estudios observacionales
DESCRIPTION
Lectura crítica de estudios observacionales, i.e., estudios de casos y controles así como los de una cohorteTRANSCRIPT
![Page 1: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/1.jpg)
prácticabasada en
evidencia
de la investigación a la toma de decisiones en salud
Oxygen therapy for acute myocardial infarction (Review)
Cabello JB, Burls A, Emparanza JI, Bayliss S, Quinn T
This is a reprint of a Cochrane review, prepared and maintained by The Cochrane Collaboration and published in The Cochrane Library2010, Issue 6
http://www.thecochranelibrary.com
Oxygen therapy for acute myocardial infarction (Review)
Copyright © 2010 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
![Page 2: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/2.jpg)
Estudios observacionales
casos y controles&cohortes
Oxygen therapy for acute myocardial infarction (Review)
Cabello JB, Burls A, Emparanza JI, Bayliss S, Quinn T
This is a reprint of a Cochrane review, prepared and maintained by The Cochrane Collaboration and published in The Cochrane Library2010, Issue 6
http://www.thecochranelibrary.com
Oxygen therapy for acute myocardial infarction (Review)
Copyright © 2010 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
![Page 3: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/3.jpg)
Tocino
• incrementa el riesgo de cáncer colorrectal en un 20%
![Page 4: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/4.jpg)
¿Qué significa?
a. El 20% de la gente que come tocino tendrá cáncer colorrectal alguna vez en su vida
b. El 20% de los cánceres colorrectales son producidos por haber comido tocino
c. 1 de cada100 personas que come tocino, tendrá cáncer de colon por esta causa.
d. Si como tocino, tengo un 20% (cada año) de probabilidades de tener cáncer colorrectal.
e. Mi riesgo basal de cáncer colorrectal, se incrementa un 20% por comer tocino.
![Page 5: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/5.jpg)
Los pasos de la Medicina Basada en Evidencia
PILAR
Preguntar
Indagar/buscar
Leer críticamente
Aplicar
Repasar
![Page 6: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/6.jpg)
Lectura crítica✓Validez✓Importancia✓Aplicabilidad
![Page 7: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/7.jpg)
Lectura crítica de un estudio observacional
• ¿Es el estudio válido?
• ¿Cuáles son los resultados?
• ¿Puedo aplicar los resultados a mi paciente?
![Page 8: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/8.jpg)
¿Qué tipo de estudio debo buscar?
![Page 9: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/9.jpg)
ejemplos
![Page 10: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/10.jpg)
¿Vacunas producen autismo?
Tomo a un paciente que tiene autismo
⚇
![Page 11: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/11.jpg)
Presentó el antecedente de que fue vacunado en la época que inició con los síntomas
⚇Conclusión: la vacuna produjo el autismo
![Page 12: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/12.jpg)
Reporte de un caso
![Page 13: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/13.jpg)
Observo varios pacientes con autismo
evalúo cuántos estuvieron expuestos a la vacuna
⚇⚇⚇⚇⚇⚇⚇⚇⚇⚇
![Page 14: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/14.jpg)
Conclusión: vacuna produjo autismo
⚇⚇⚇⚇⚇⚇⚇⚇⚇⚇
El 80% tenían fueron expuestos
![Page 15: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/15.jpg)
Serie de casos
![Page 16: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/16.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇
⚇⚇⚇ ⚇
⚇
⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇
⚇⚇⚇ ⚇
⚇
⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente pasado
Enfe
rmos
Sano
s
![Page 17: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/17.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇
⚇⚇⚇ ⚇
⚇
⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇
⚇⚇⚇ ⚇
⚇
⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente pasado
Enfe
rmos
Sano
s
![Page 18: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/18.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇ ⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇ ⚇
⚇⚇
⚇⚇⚇ ⚇
⚇
⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇
⚇⚇⚇ ⚇
⚇
⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente pasado
Enfe
rmos
Sano
s
![Page 19: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/19.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇ ⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇ ⚇
⚇⚇
⚇⚇⚇ ⚇
⚇
⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇
⚇⚇⚇ ⚇
⚇
⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente pasado
Enfe
rmos
Sano
sExpuestosNo
expuestos
![Page 20: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/20.jpg)
Casos y controles
![Page 21: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/21.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente futuro
![Page 22: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/22.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente futuro
![Page 23: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/23.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente futuro
![Page 24: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/24.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente futuro
![Page 25: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/25.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇ ⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente futuro
![Page 26: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/26.jpg)
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇⚇
⚇⚇⚇⚇⚇ ⚇
⚇⚇
⚇⚇⚇⚇
⚇⚇⚇ ⚇⚇
⚇⚇ ⚇
⚇⚇⚇⚇⚇⚇⚇
⚇⚇⚇
presente futuro
![Page 27: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/27.jpg)
Cohorte
![Page 28: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/28.jpg)
Pacientes sanos en edad de vacunarse... 200
1 1
99 99
100 100
P
niños
I C
autismo
Vacuna Placebo
+
-
azar
O
![Page 29: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/29.jpg)
Ensayo clínico aleatorio
![Page 30: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/30.jpg)
Síntesis
= Revisiones sistemáticas
entre otros...
Ensayos clínicos individuales
![Page 31: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/31.jpg)
¿asociación = causalidad?
![Page 32: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/32.jpg)
Ileal-lymphoid-nodular hyperplasia, non-specific colitis, andpervasive developmental disorder in childrenA J Wakefield, S H Murch, A Anthony, J Linnell, D M Casson, M Malik, M Berelowitz, A P Dhillon, M A Thomson, P Harvey, A Valentine, S E Davies, J A Walker-Smith
THE LANCET • Vol 351 • February 28, 1998 637
Early report
EARLY REPORT
Summary
Background We investigated a consecutive series ofchildren with chronic enterocolitis and regressivedevelopmental disorder.
Methods 12 children (mean age 6 years [range 3–10], 11boys) were referred to a paediatric gastroenterology unitwith a history of normal development followed by loss ofacquired skills, including language, together with diarrhoeaand abdominal pain. Children underwentgastroenterological, neurological, and developmentalassessment and review of developmental records.Ileocolonoscopy and biopsy sampling, magnetic-resonanceimaging (MRI), electroencephalography (EEG), and lumbarpuncture were done under sedation. Barium follow-throughradiography was done where possible. Biochemical,haematological, and immunological profiles wereexamined.
Findings Onset of behavioural symptoms was associated,by the parents, with measles, mumps, and rubellavaccination in eight of the 12 children, with measlesinfection in one child, and otitis media in another. All 12children had intestinal abnormalities, ranging fromlymphoid nodular hyperplasia to aphthoid ulceration.Histology showed patchy chronic inflammation in the colonin 11 children and reactive ileal lymphoid hyperplasia inseven, but no granulomas. Behavioural disorders includedautism (nine), disintegrative psychosis (one), and possiblepostviral or vaccinal encephalitis (two). There were nofocal neurological abnormalities and MRI and EEG testswere normal. Abnormal laboratory results were significantlyraised urinary methylmalonic acid compared with age-matched controls (p=0·003), low haemoglobin in fourchildren, and a low serum IgA in four children.
Interpretation We identified associated gastrointestinaldisease and developmental regression in a group ofpreviously normal children, which was generally associatedin time with possible environmental triggers.
Lancet 1998; 351: 637–41See Commentary page
Inflammatory Bowel Disease Study Group, University Departmentsof Medicine and Histopathology (A J Wakefield FRCS, A Anthony MB,J Linnell PhD, A P Dhillon MRCPath, S E Davies MRCPath) and theUniversity Departments of Paediatric Gastroenterology (S H Murch MB, D M Casson MRCP, M Malik MRCP,M A Thomson FRCP, J A Walker-Smith FRCP,), Child and AdolescentPsychiatry (M Berelowitz FRCPsych), Neurology (P Harvey FRCP), andRadiology (A Valentine FRCR), Royal Free Hospital and School ofMedicine, London NW3 2QG, UK
Correspondence to: Dr A J Wakefield
IntroductionWe saw several children who, after a period of apparentnormality, lost acquired skills, including communication.They all had gastrointestinal symptoms, includingabdominal pain, diarrhoea, and bloating and, in somecases, food intolerance. We describe the clinical findings,and gastrointestinal features of these children.
Patients and methods12 children, consecutively referred to the department ofpaediatric gastroenterology with a history of a pervasivedevelopmental disorder with loss of acquired skills and intestinalsymptoms (diarrhoea, abdominal pain, bloating and foodintolerance), were investigated. All children were admitted to theward for 1 week, accompanied by their parents.
Clinical investigationsWe took histories, including details of immunisations andexposure to infectious diseases, and assessed the children. In 11cases the history was obtained by the senior clinician (JW-S).Neurological and psychiatric assessments were done byconsultant staff (PH, MB) with HMS-4 criteria.1 Developmentalhistories included a review of prospective developmental recordsfrom parents, health visitors, and general practitioners. Fourchildren did not undergo psychiatric assessment in hospital; allhad been assessed professionally elsewhere, so these assessmentswere used as the basis for their behavioural diagnosis.
After bowel preparation, ileocolonoscopy was performed bySHM or MAT under sedation with midazolam and pethidine.Paired frozen and formalin-fixed mucosal biopsy samples weretaken from the terminal ileum; ascending, transverse,descending, and sigmoid colons, and from the rectum. Theprocedure was recorded by video or still images, and werecompared with images of the previous seven consecutivepaediatric colonoscopies (four normal colonoscopies and threeon children with ulcerative colitis), in which the physicianreported normal appearances in the terminal ileum. Bariumfollow-through radiography was possible in some cases.
Also under sedation, cerebral magnetic-resonance imaging(MRI), electroencephalography (EEG) including visual, brainstem auditory, and sensory evoked potentials (where compliancemade these possible), and lumbar puncture were done.
Laboratory investigationsThyroid function, serum long-chain fatty acids, andcerebrospinal-fluid lactate were measured to exclude knowncauses of childhood neurodegenerative disease. Urinarymethylmalonic acid was measured in random urine samples fromeight of the 12 children and 14 age-matched and sex-matchednormal controls, by a modification of a technique describedpreviously.2 Chromatograms were scanned digitally oncomputer, to analyse the methylmalonic-acid zones from casesand controls. Urinary methylmalonic-acid concentrations inpatients and controls were compared by a two-sample t test.Urinary creatinine was estimated by routine spectrophotometricassay.
Children were screened for antiendomyseal antibodies andboys were screened for fragile-X if this had not been done
![Page 33: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/33.jpg)
![Page 34: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/34.jpg)
Ileal-lymphoid-nodular hyperplasia, non-specific colitis, andpervasive developmental disorder in childrenA J Wakefield, S H Murch, A Anthony, J Linnell, D M Casson, M Malik, M Berelowitz, A P Dhillon, M A Thomson, P Harvey, A Valentine, S E Davies, J A Walker-Smith
THE LANCET • Vol 351 • February 28, 1998 637
Early report
EARLY REPORT
Summary
Background We investigated a consecutive series ofchildren with chronic enterocolitis and regressivedevelopmental disorder.
Methods 12 children (mean age 6 years [range 3–10], 11boys) were referred to a paediatric gastroenterology unitwith a history of normal development followed by loss ofacquired skills, including language, together with diarrhoeaand abdominal pain. Children underwentgastroenterological, neurological, and developmentalassessment and review of developmental records.Ileocolonoscopy and biopsy sampling, magnetic-resonanceimaging (MRI), electroencephalography (EEG), and lumbarpuncture were done under sedation. Barium follow-throughradiography was done where possible. Biochemical,haematological, and immunological profiles wereexamined.
Findings Onset of behavioural symptoms was associated,by the parents, with measles, mumps, and rubellavaccination in eight of the 12 children, with measlesinfection in one child, and otitis media in another. All 12children had intestinal abnormalities, ranging fromlymphoid nodular hyperplasia to aphthoid ulceration.Histology showed patchy chronic inflammation in the colonin 11 children and reactive ileal lymphoid hyperplasia inseven, but no granulomas. Behavioural disorders includedautism (nine), disintegrative psychosis (one), and possiblepostviral or vaccinal encephalitis (two). There were nofocal neurological abnormalities and MRI and EEG testswere normal. Abnormal laboratory results were significantlyraised urinary methylmalonic acid compared with age-matched controls (p=0·003), low haemoglobin in fourchildren, and a low serum IgA in four children.
Interpretation We identified associated gastrointestinaldisease and developmental regression in a group ofpreviously normal children, which was generally associatedin time with possible environmental triggers.
Lancet 1998; 351: 637–41See Commentary page
Inflammatory Bowel Disease Study Group, University Departmentsof Medicine and Histopathology (A J Wakefield FRCS, A Anthony MB,J Linnell PhD, A P Dhillon MRCPath, S E Davies MRCPath) and theUniversity Departments of Paediatric Gastroenterology (S H Murch MB, D M Casson MRCP, M Malik MRCP,M A Thomson FRCP, J A Walker-Smith FRCP,), Child and AdolescentPsychiatry (M Berelowitz FRCPsych), Neurology (P Harvey FRCP), andRadiology (A Valentine FRCR), Royal Free Hospital and School ofMedicine, London NW3 2QG, UK
Correspondence to: Dr A J Wakefield
IntroductionWe saw several children who, after a period of apparentnormality, lost acquired skills, including communication.They all had gastrointestinal symptoms, includingabdominal pain, diarrhoea, and bloating and, in somecases, food intolerance. We describe the clinical findings,and gastrointestinal features of these children.
Patients and methods12 children, consecutively referred to the department ofpaediatric gastroenterology with a history of a pervasivedevelopmental disorder with loss of acquired skills and intestinalsymptoms (diarrhoea, abdominal pain, bloating and foodintolerance), were investigated. All children were admitted to theward for 1 week, accompanied by their parents.
Clinical investigationsWe took histories, including details of immunisations andexposure to infectious diseases, and assessed the children. In 11cases the history was obtained by the senior clinician (JW-S).Neurological and psychiatric assessments were done byconsultant staff (PH, MB) with HMS-4 criteria.1 Developmentalhistories included a review of prospective developmental recordsfrom parents, health visitors, and general practitioners. Fourchildren did not undergo psychiatric assessment in hospital; allhad been assessed professionally elsewhere, so these assessmentswere used as the basis for their behavioural diagnosis.
After bowel preparation, ileocolonoscopy was performed bySHM or MAT under sedation with midazolam and pethidine.Paired frozen and formalin-fixed mucosal biopsy samples weretaken from the terminal ileum; ascending, transverse,descending, and sigmoid colons, and from the rectum. Theprocedure was recorded by video or still images, and werecompared with images of the previous seven consecutivepaediatric colonoscopies (four normal colonoscopies and threeon children with ulcerative colitis), in which the physicianreported normal appearances in the terminal ileum. Bariumfollow-through radiography was possible in some cases.
Also under sedation, cerebral magnetic-resonance imaging(MRI), electroencephalography (EEG) including visual, brainstem auditory, and sensory evoked potentials (where compliancemade these possible), and lumbar puncture were done.
Laboratory investigationsThyroid function, serum long-chain fatty acids, andcerebrospinal-fluid lactate were measured to exclude knowncauses of childhood neurodegenerative disease. Urinarymethylmalonic acid was measured in random urine samples fromeight of the 12 children and 14 age-matched and sex-matchednormal controls, by a modification of a technique describedpreviously.2 Chromatograms were scanned digitally oncomputer, to analyse the methylmalonic-acid zones from casesand controls. Urinary methylmalonic-acid concentrations inpatients and controls were compared by a two-sample t test.Urinary creatinine was estimated by routine spectrophotometricassay.
Children were screened for antiendomyseal antibodies andboys were screened for fragile-X if this had not been done
RETRACTED
![Page 35: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/35.jpg)
FRAUDE
![Page 36: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/36.jpg)
![Page 37: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/37.jpg)
![Page 38: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/38.jpg)
TABACO i nc rementa e l r iesgo de par to prematuro
![Page 39: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/39.jpg)
¿Cómo demostrarlo?
![Page 40: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/40.jpg)
¿mediante un ECA?
PMujeres
embarazadas
I ó E C
Parto pretérmino
• No ético
Fumar Cigarrillos
FumarPlacebo
OT
+
-
A
![Page 41: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/41.jpg)
Cohorte
PMujeres
embarazadas
E C
Parto pretérmino
• ¿Ético?
Fuma cigarrillos No fuma
OT
+
-
![Page 42: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/42.jpg)
Casos y controles
PMujeres elegibles
E C
Parto pretérmino
Fumó Cigarrillos No fumó
OT
+
-
Grupos con y sin desenlace
Evalúan la exposición o no
exposición
![Page 43: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/43.jpg)
Se
sg
o
Recomendaciones de experto
Transversales(cross-sectional)
Observaciones clínicas(serie de casos, reporte de un
caso)
casos y controles
cohorte
Ensayo clínico aleatorio
Revisión sistemática
Analíticos
Descriptivos
Observacional
Experimental
Síntesis
![Page 44: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/44.jpg)
![Page 45: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/45.jpg)
![Page 46: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/46.jpg)
¿Son%válidos%los%resultados?%
1. ¿El&estudio&se¢ra&en&un&tema&claramente&definido?&– PISTA:'Una'pregunta'se'puede'
definir'en'términos'de:'• La'población'estudiada.'• Los'factores'de'riesgo'estudiados.'
• Si'el'estudio'intentó'detectar'un'efecto'beneficioso'o'perjudicial.%
Sí%
No%sé%
No%
![Page 47: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/47.jpg)
¿Son%válidos%los%resultados?%
2. ¿Los'autores'han'u/lizado'un'método'apropiado'para'responder'a'la'pregunta?'
• PISTA:'Considerar:'– ¿Es'el'estudio'de'Casos'y'Controles'una'forma'adecuada'para'contestar'la'pregunta'en'estas'circunstancias?'(¿Es'el'resultado'a'estudio'raro'o'prejudicial?)'
– ¿El'estudio'está'dirigido'a'contestar'la'pregunta?%
Sí%
No%sé%
No%
![Page 48: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/48.jpg)
¿Son%válidos%los%resultados?%2%preguntas%de%detalle%2%
Sí%
No%sé%
No%
3. ¿Los'casos'se'reclutaron'/'incluyeron'de'una'forma'aceptable?'PISTA:'Se'trata'de'buscar'sesgo'de'selección'que'pueda'
comprometer'la'validez'de'los'hallazgos'
– ¿Los'casos'se'han'definido'de'forma'precisa?'– ¿Los'casos'son'representaBvos'de'una'población'
definida'(geográfica'y/o'temporalmente)?'– ¿Se'estableció'un'sistema'fiable'para'la'selección'de'
todos'los'casos?'– ¿Son'incidencia'o'prevalencia?'– ¿Hay'algo'“especial”'que'afecta'a'los'casos?'– ¿El'marco'temporal'del'estudio'es'relevante'en'
relación'a'la'enfermedad/exposición?'– ¿Se'seleccionó'un'número'suficiente'de'casos?'– ¿Tiene'potencia'estadísBca?%
![Page 49: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/49.jpg)
¿Son%válidos%los%resultados?%4. ¿Los'controles'se'seleccionaron'
de'una'manera'aceptable?'
PISTA:'Se'trata'de'buscar'sesgo'de'selección'que'pueda'comprometer'la'generalizabilidad'de'los'hallazgos.'
• ¿Los'controles'son'representa?vos'de'una'población'definida'(geográfica'y/o'temporalmente)?'
• ¿Hay'algo'“especial”'que'afecta'a'los'controles?'• ¿Hay'muchos'no'respondedores?'• ¿Podrían'ser'los'no'respondedores'de'alguna'
manera'diferentes'al'resto?'• ¿Han'sido'seleccionados'de'forma'aleatorizada,'
basados'en'una'población?'• ¿Se'seleccionó'un'número'suficiente'de'controles?%
Sí%
No%sé%
No%
![Page 50: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/50.jpg)
¿Son%válidos%los%resultados?%
5. ¿La&exposición&se&midió&de&forma&precisa&con&el&fin&de&minimizar&posibles&sesgos?&
PISTA:'Estamos'buscando'sesgos'de'medida,'re8rada'o'de'clasificación:'
• ¿Se'definió'la'exposición'claramente'y'se'midió'ésta'de'forma'precisa?'
• ¿Los'autores'u8lizaron'variables'obje8vas'o'subje8vas?'• ¿Las'variables'reflejan'de'forma'adecuada'aquello'que'se'
suponen'que'8ene'que'medir?'(han'sido'validadas).'• ¿Los'métodos'de'medida'fueron'similares'tanto'en'los'
casos'como'en'los'controles?'• Cuando'fue'posible'¿se'u8lizó'en'el'estudio'cegamiento?'• ¿La'relación'temporal'es'correcta'(la'exposición'de'interés'
precede'al'resultado/variable'de'medida)?%
Sí%
No%sé%
No%
![Page 51: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/51.jpg)
Para que haya asociación válida y pensar en causalidad, hay que evaluar...
• El sesgo
• Factores de confusión
• El papel del azar
![Page 52: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/52.jpg)
Sesgos
• Sesgos de selección
• Berksonian
• Sesgo del respondedor (response bias)
• Sesgos de información
• Sesgo de clasificación (missclassification bias)
• Sesgo de recuerdo (recall bias)
• Sesgo de reporte (reporting bias)
• Sesgo de detección (surveillance bias)
![Page 53: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/53.jpg)
Sesgos
• Sesgos de selección
• Berksonian - cuando se usa la frecuencia de admisiones hospitalarias; son distintas para los que tienen enfermedad que en los controles
• Sesgo del respondedor (response bias) - aquellos que aceptan entrar a un estudio son distintos a los que no (voluntarios son distintos)
• ... El autor determina los criterios de elección y los aplica diferente en los casos que en los controles
![Page 54: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/54.jpg)
Sesgos
• Sesgos de información
• Sesgo de clasificación (missclassification bias)
- mal clasifican los casos y los controles por indagar más al momento de ingresarlos al estudio, p. ej., casos de TDAH vs controles, al momento de evaluar si los controles son o no TDAH, puede que a ellos no se les haga las preguntas más a fondo o no se hagan pruebas de detección.
• Sesgo de recuerdo (recall bias)
- Mujeres que tuvieron aborto pueden recordar más que estuvieron expuestas a campos magnéticos de antenas, que aquellas (controles) que no tuvieron un aborto.
![Page 55: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/55.jpg)
Sesgos
• Sesgos de información
• Sesgo de reporte (reporting bias)
- Los casos no reportan ciertas actitudes o problemas; p. ej., los adictos pueden no decir que consumieron drogas
• Sesgo de detección (surveillance, ascertainment bias)
- mujeres que toman la píldora tendrán más exámenes pap = más cáncer se detecta en ellas. Al momento de hacer un casos-controles, los casos (cáncer) habrán tomado más píldoras y se creerá que las píldoras producen cáncer.
![Page 56: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/56.jpg)
Channeling effect (tiro por la culata)
• Acto #1: se crea el ketoprofeno
• Acto #2: los creadores dicen que produce menos sangrado gastrointestinal (SGI) y así lo promocionan
• Acto #3: los doctores se lo dan a los pacientes con alto riesgo de sangrar (claro, porque produce menos sangrados)
• Resultado: posteriormente, al hacer un estudio de cohorte o casos-controles, los resultados dicen que los pacientes que toman ketoprofeno, sangran más que los que toman otros AINEs
![Page 57: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/57.jpg)
¿Son%válidos%los%resultados?%6"A."¿Qué"factores"de"confusión"han"tenido"en"
cuenta"los"autores?"• Haz$una$lista$de$los$factores$que$piensas$que$son$
importantes$y$que$los$autores$han$omi6do$(gené6cos,$ambientales,$socioeconómicos).$
B."¿Han"tenido"en"cuenta"los"autores"el"potencial"de"los"factores"de"confusión"enl"diseño"y/o"análisis?"
PISTA:$Busca$restricciones$en$el$diseño$y$técnica,$por$ejemplo,$análisis$de$modelización,$estra6ficación,$regresión$o$de$sensibilidad$para$corregir,$controlar$o$ajustar$los$factores$de$confusión.%
Sí%
No%sé%
No%
![Page 58: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/58.jpg)
Algo%no%está%bien…%nuestro%aire%es%limpio,%el%agua%es%pura,%hacemos%
ejercicio%todo%el%día,%todo%lo%que%comemos%es%“orgánico%y%natural”…%
sin%embargo,%nuestro%promedio%de%vida%sigue%siendo%menos%de%30%
años.%
Factores de confusión
![Page 59: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/59.jpg)
Café
Infartos
Tabaquismo
¿Factor confusor?
![Page 60: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/60.jpg)
Cigarrillos
Suicidio
Depresión
¿Factor confusor?
![Page 61: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/61.jpg)
![Page 62: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/62.jpg)
4 casas pérdida x casa$
100,000
1,000,000
camiones usados
![Page 63: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/63.jpg)
CONCLUSIONES
• Entre más camiones de bomberos se usen, más dinero se pierde.
• Es necesario reducir el número de camiones en los incendios
![Page 64: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/64.jpg)
Asociación no siempre es causalidad
• La vacuna MMR produce autismo
• Adenovirus causa obesidad
• Los divorcios son producidos por el incremento de los precios de la cerveza
• Tamaño del zapato e inteligencia
• Tomar café es malo para la salud
• Niños que desayunan son más sanos e inteligentes
![Page 65: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/65.jpg)
Criterios de Bradford Hills
• Fuerza de asociación
• Credibilidad biológica
• Especificidad
• Consistencia
• Temporalidad
• Dosis-respuesta
• Analogía
• Evidencia experimental
• Coherencia
![Page 66: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/66.jpg)
Carrera pueblerina
![Page 67: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/67.jpg)
Hipótesis
• Los hombres serán más veloces que las mujeres
![Page 68: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/68.jpg)
Primera ronda
gana
![Page 69: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/69.jpg)
Primera ronda
No es justo, el promedio de PESO era mayor en las mujeres, eso influye en el resultado
final
Es necesario ajustar el peso...
![Page 70: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/70.jpg)
Segunda ronda
gana
![Page 71: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/71.jpg)
Segunda ronda
No es justo, el promedio de EDAD era mayor en las mujeres, eso influye en el resultado
final
Es necesario ajustar la edad...
![Page 72: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/72.jpg)
tercer ronda
gana
![Page 73: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/73.jpg)
tercer ronda
No es justo, el promedio de LARGO
DEL CABELLO
era mayor en las mujeres, eso influye
en el resultado
final
Es necesario ajustar...
¡Un momento...!
![Page 74: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/74.jpg)
¿Cuáles(son(los(resultados?(
7"¿Cuáles"son"los"resultados"de"este"estudio?"PISTA:'• ¿Cuáles'son'los'resultados'netos?'• ¿El'análisis'es'apropiado'para'su'diseño?'• ¿Cuán'fuerte'es'la'relación'de'asociación'
entre'la'exposición'y'el'resultado'(mira'los'odds'raAo'(OR))?'
• ¿Los'resultados'se'han'ajustado'a'los'posibles'factores'de'confusión'y,'aun'así,'podrían'estos'factores'explicar'la'asociación?'
• ¿Los'ajustes'han'modificado'de'forma'sustancial'los'OR?(
Sí(
No(sé(
No(
![Page 75: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/75.jpg)
¿Cuáles(son(los(resultados?(
8"¿Cuál"es"la"precisión"de"los"resultados?"• ¿Cuál"es"la"precisión"de"la"es5mación"del"riesgo?"
PISTA:'• Tamaño'del'valor'de'P.'• Tamaño'de'los'intervalos'de'confianza.'• ¿Los'autores'han'considerado'todas'las'variables'importantes?'
• ¿Cuál'fue'el'efecto'de'los'individuos'que'rechazaron'el'parDcipar'en'la'evaluación?(
Sí(
No(sé(
No(
![Page 76: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/76.jpg)
Cohorte
PMujeres
embarazadas
E C
Parto pretérmino
• resultados
• OR=3.2 (1.42 a 7.23)
Fuma cigarrillos No fuma
OT
+
-
n=251 n=1992
25 88
1904226
![Page 77: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/77.jpg)
¿Cuáles(son(los(resultados?(
9"¿Te"crees"los"resultados?"PISTA:'
• ¡Un'efecto'grande'es'di6cil'de'ignorar!'• ¿Puede'deberse'al'azar,'sesgo'o'confusión?'• ¿El'diseño'y'los'métodos'de'este'estudio'son'
lo'suficientemente'defectuosos'para'hacer'
que'los'resultados'sean'poco'creíbles?'
• Considera'los'criterios'de'Bradford'Hills'(por'ejemplo,'secuencia'temporal,'gradiente'
dosisOrespuesta,'fortaleza'de'asociación,'
verosimilitud'biológica).(
Sí(
No(sé(
No(
![Page 78: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/78.jpg)
¿Son%los%resultados%aplicables%a%tu%medio?%
¿merece%la%pena%con4nuar?!10%¿Se%pueden%aplicar%los%resultados%a%tu%medio?%
PISTA:'Considera'si…'• Los'pacientes'cubiertos'por'el'estudio'pueden'ser'suficientemente'diferentes'de'los'de'tu'área.'
• Tu'medio'parece'ser'muy'diferente'al'del'estudio.'
• ¿Puedes'es@mar'los'beneficios'y'perjuicios'en'tu'medio?!
Sí!
No!sé!
No!
![Page 79: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/79.jpg)
¿Son%los%resultados%aplicables%a%tu%medio?!
11%¿Los%resultados%de%este%estudio%coinciden%con%otra%evidencia%disponible?%
PISTA:'
• Considera'toda'la'evidencia'disponible:'Ensayos'Clínicos'aleatorizados,'Revisiones'Sistemá?cas,'Estudios'de'Cohorte'y'Estudios'de'Casos'y'Controles,'así'como'su'consistencia.!
Sí!
No!sé!
No!
![Page 80: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/80.jpg)
¿Momios?
odds
![Page 81: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/81.jpg)
Odds vs probabilidad
Pastel de reyes con un muñeco escondido dentro del mismo.
Partido en cuatro partes
Si tomas un pedazo...
¿Qué probabilidad hay de sacar el muñeco?
![Page 82: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/82.jpg)
En probabilidad
1 de 4
1/4 = 0.25 ó 25%
![Page 83: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/83.jpg)
En momios
1 de sacarlo
vs
3 de no sacarlo
1 a 3
1/3 = 0.333
![Page 84: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/84.jpg)
Cómo convertir probabilidad a odds (momios)
odds = p/1-podds = 0.25/1-0.25odds =0.25/0.75odds = 0.333
![Page 85: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/85.jpg)
Cómo convertir odds a probabilidad
p= odds/1+oddsp= 0.33/1+0.33p=0.33/1.33p= 0.25
![Page 86: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/86.jpg)
PMujeres
embarazadas
E C
Parto pretérmino
Fuma cigarrillos No fuma
OT
+
-
n=251 n=1992
25 88
1904226
Odds de parto pretérmino en
grupo de exposición
Odds de parto pretérmino en grupo control
0.11
0.04OR crudo = 2.7
![Page 87: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/87.jpg)
PMujeres
embarazadas
E C
Parto pretérmino
• resultados
• OR=3.2 (1.42 a 7.23)
Fuma cigarrillos No fuma
OT
+
-
n=251 n=1992
25 88
1904226
0.1 0.5 0.7 1 2 3 5 7
IC 95%
![Page 88: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/88.jpg)
Tocino
• incrementa el riesgo de cáncer colorrectal en un 20%
![Page 89: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/89.jpg)
¿Qué significa?
a. El 20% de la gente que come tocino tendrá cáncer colorrectal alguna vez en su vida
b. El 20% de los cánceres colorrectales son producidos por haber comido tocino
c. 1 de cada100 personas que come tocino, tendrá cáncer de colon por esta causa.
d. Si como tocino, tengo un 20% (cada año) de probabilidades de tener cáncer colorrectal.
e. Mi riesgo basal de cáncer colorrectal, se incrementa un 20% por comer tocino.
![Page 90: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/90.jpg)
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
TOCINO NO TOCINO
![Page 91: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/91.jpg)
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � ☹ ☹ ☹ ☹ ☹
TOCINO NO TOCINO
5 con cáncer
![Page 92: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/92.jpg)
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � ☹ ☹ ☹ ☹ ☹ ☹
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � � � � � �
� � � � � ☹ ☹ ☹ ☹ ☹
TOCINO NO TOCINO
5 con cáncer6 con cáncer
![Page 93: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/93.jpg)
200
6 5
94 95
100 100
P
I C
OCÁNCER
NO CÁNCER
TOCINO Control
PEE PEC
ODDS 5/95
= 0.052
ODDS 6/94
= 0.063
![Page 94: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/94.jpg)
ODDS 5/95
= 0.052
ODDS 6/94
= 0.063
![Page 95: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/95.jpg)
ODDS 5/95
= 0.052
ODDS 6/94
= 0.063=1.21
![Page 96: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/96.jpg)
Tocino
FelicidadAlegríaDicha
![Page 97: Estudios Observacionales](https://reader035.vdocuments.net/reader035/viewer/2022081401/55842949d8b42a86478b4dc9/html5/thumbnails/97.jpg)
GRACIAS