clinical preventive medicine
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Clinical Preventive Medicine. Wang Min ( 王敏) School of Public health and general medicine. Clinical Preventive Medicine ( CPM ) - PowerPoint PPT PresentationTRANSCRIPT
Clinical Preventive MedicineClinical Preventive Medicine
Wang Min (王敏)School of Public health and general medicinSchool of Public health and general medicin
ee
Clinical Preventive Medicine
( CPM ) those personal health services provided in the
context of clinical medicine, the purpose of which is to maintain health and reduce the risk of disease and untimely disease.
Preventive services were divided into three categories
Screening tests (筛检) Counseling interventions (健康咨询) and health e
ducation (健康教育) The Periodic Health Examination (周期性健康检
查) Nutrition guidance (营养指导) Immunizations (免疫预防) Chemoprophylaxis (化学预防)
Screening
Screening is a public health service in which members of a defined population, who do not necessarily perceive they are at risk of, or are already affected by a disease or its complications, are asked a question or offered a test, to identify those individuals who are more likely to be helped than harmed by further tests or treatment to reduce the risk of a disease or its complications.
The Purpose of Screening:
to find persons with risk factors in which preventive interventions could be used or to identify individual with early or asymptomatic treatable disease.
The principle of screening test:1.The disease should be an important health problem ,
having severe consequences or high prevalence2. The detection of rare diseases may lead to high cost-
benefit ratios. 3.The epidemiology and natural history of the condition,
including development from latent to declared disease, should be adequately understood and there should be a detectable risk factor, disease marker, latent period or early symptomatic stage.
4.An effective preventive intervention or treatment should be available.
5.All the cost-effective primary prevention interventions should have been implemented as far as possible.
The test
1.There should be a simple, safe, precise and validated test.
2.The distribution of the test values in the target population should be known and a suitable cut-off level defined.
3.The test should be acceptable to the population 4.There should be an agreed policy on the further
diagnostic investigation of individuals with a positive test result and on the choices available to those individuals.
The treatment
1.There should be an effective treatment or intervention for patients identified through early detection, with evidence of early treatment leading to better outcomes than late treatment.
2.There should be agreed evidence-based policies covering which individuals should be offered treatment and the appropriate treatment to be offered.
3.Clinical management of the condition and patient outcomes should be optimised by all health care providers prior to participation in a screening programme.
screening test must satisfy two major requirements to be considered effective:
1The test must be able to detect the target condition earlier than without screening and with sufficient accuracy to avoid producing large numbers of false-positive and false-negative results (accuracy of screening test ).
2 Screening for and treating persons with early disease should improve the likelihood of favorable health outcomes (e.g., reduced disease-specific morbidity or mortality) compared to treating patients when they present with signs or symptoms of the disease (effectiveness of early detection ).
Pros and cons of screening
Advantages Disadvantages
Improved prognosis for some Cases Less radical treatment Resource savings Reassurance
Longer morbidity for cases whose prognosis is Unaltered Overtreatment of questionable abnormalities Resource costs False reassurance of false negative people Anxiety and hazard for false positive cases Hazard of screening test
Counseling interventions
are those in which the patient receives information and advice regarding personal behaviors (e.g., diet) that could reduce the risk of subsequent illness or injury. The Task Force did not consider counseling that addresses the health-related behaviors of persons who have already developed signs and symptoms of the target condition.
Counseling interventions and health education
1. Use plain language.
2.Start with the most important information
first.
3.Use repetition to reinforce your message.
4.Ask the patient to restate the message.
5.Provide an opportunity for questions.
Counseling/Education about Disease
• Be specific and concrete. • Start with the most important information
first. • Use repetition to reinforce your message. • Ask the patient to restate the message. • Provide opportunities for questions.
What Works? • Provide information – Use multiple forms of information. – Answer questions. • Reward patients for positive behavioral change. • Tailor the intervention to the patient’s needs. • Provide feedback about the change in health status measure.
Example
What is Hypertension? Why does hypertension need to be
treated? How is hypertension treated? Managing and Preventing Hypertension • BMI 18.5 – 24.9 kg/m2
Exercise – 30 minutes per day most days of week “Moderate” alcohol consumption – Men 2 drinks or fewer per day – Women 1 drink or fewer • Increase dietary intake potassium – 3500 mg a day • Increase dietary intake potassium – 3500 mg a day
History RPHE developed with consideration of
overall financial impact and patient considerationsSpecific costs not calculatedspecific patient considerations not elicited
but board members served as surrogates
Periodic Health Examinations(RPHE: 周期性健康体检 )
The RPHE
“These recommendations are provided only as assistance for physicians making clinical decisions regarding the care of patients.” “Can not substitue for the individual judgement brought to each clinical situation by the patient’s family physician.”
AAFP Recommendations
SR Strongly Recommend: Good quality evidence exists which demonstrates substantial net benefit over harm; the intervention is perceived to be cost effective and acceptable to nearly all patients
R Recommend: Although evidence exists which demonstrates net benefit, either the benefit is only moderate in magnitude or the evidence supporting a substantial benefit is only fair. The intervention is perceived to be cost effective and acceptable to most patients.
AAFP Recommendations
NR No Recommendation Either for or Against: Either good or fair evidence exists of at least a small net benefit. Cost-effectiveness may not be known or patients may be divided about acceptability of the intervention.
RA Recommend Against: Good or fair evidence which demonstrates no net benefit over harm.
AAFP Recommendations
I Insufficient Evidence to Recommend Either for or Against: No evidence of even fair quality exists or the existing evidence is conflicting.
I-HB Healthy Behavior is identified as desirable but the effectiveness of physician’s advice and counseling is uncertain.
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Health Examination ProcessHealth Examination Process
Definitionof needs
Process:- planning- implementation- health education- recommendat-ions
Results Evaluation
Example
Immunization
Terms Immunization – conferring immunity by
artificial means Vaccination – conferring immunity to a
disease using a vaccine or special antigenic material to stimulate the formation of appropriate antibodies
Vaccine – preparation of antigenic material – stimulates Ab production – confers active immunity
vs.disease Latin “vacca” = cow (from cowpox)
ImmunizationUsing vaccines or antibody-containing
preparations to provide immune protection vs. specific diseases
PassivePreformed antibodies - another hostProtect individual exposed to disease
Active (vaccines)Modified / purified pathogens or their
productsStimulate host to produce own specific
immunity
Passive Immunization
IgG - immediate protection - no memory Standard Igs (human, animals) Non-specific
Pooled plasma from donors Igs vs. many common viruses
Human hyperimmune serum (high titre) SpecificFrom donor c. high titre Abs to specific virusAgainst specific (single) virus
Passive Immunization
Indications: Exposure has occurred, or is expected to occur soon No effective vaccine exists or time req’d too short Underlying illness – prevents admin. vaccineE.g. uses: Standard Ig – Congenit./acq. Ig deficiency, prevent Hep
A Rabies Ig (HRIg) – post-exposure prophylaxis VZ Ig – post-exposure prophylaxis if at high risk CMV Ig – passive imm. renal transplant recipient
Vaccines - Active
Injection of viable / non-viable pathogens or purified pathogen productsResponse as if being attacked by intact
organism Live / inactivated / DNA vaccines Effective starting after ~2 wks to few
months Prolonged immunity <-- own antibodies
produced
Active vaccine - Live attenuated pathogens
Multiplies inside human host & provides strong antigenic stimulation
Provides prolonged immunity (yrs to life), often with single dose
Vaccine often provides cell-meditated immunity
Disadvantage – can revert to virulent form--> Do not give to immunocomprom., pregnant
Active - Killed micro-organism
Does not multiply in human host Immune response depends on Ag content
of vaccine Multiple doses of vaccine required with
subsequent booster doses Provides little cell-mediated immunity No possibility of a vaccine-assoc. infection
Active - Microbial extracts
Extracted molecules (Ags): from pathogen from acellular (non-infectious) filtrate of
culture medium in which org. grown recombinant DNA techniques
Vaccines can be prepared with toxoids (=derivatives of exotoxins) Used when pathogenicity of org. is due to secreted
toxin E.g., tetanus, diphtheria
Active - Toxoids
Derivatives of bacterial exotoxins Rendered non-toxic But remain immunogenic Admin – IM, SC E.g.
TetanusDiphtheria
Attenuated pathogen
Killed pathogen
Microbial extract / product
Bacterial Diseases
Typhoid (PO)
BCG (M. bovis)
(Salmonella)
Typhoid fever
Cholera
Pertussis
Plague (Y. pestis)
Anthrax
B. pertussis Ag
*Hib
Diphtheria (Tox.)
*Meningococcal
*Pneumococcal
Tetanus (Tox.)
Viral Diseases
Measles
Mumps
Rubella
Chickenpox
Polio (Sabin - PO)
Yellow fever
Polio (Salk)
Hep. A
Influenza
Rabies
Japanese encephalitis
Hep. B
Vaccine components
Age & Immunity
Passive immunity from motherMaternal IgG passes the placentaBefore and at birth – IgG presentBreast milk – secretory Abs (GI & resp. tract)
Active Immunization Infant begins to produce Abs in 1st yrStart immunization at 2 months (usually)
Elderly --> weaker immune response
Problems with vaccines
Localized - at site of injection Anaphylaxis to Ag or non-microbial
content vaccine (eggs) Contamination with pathogen Reversion of attenuation Lack of efficacy if another concurrent
infection (rubella & polio vaccine) Organisms with lots of serotypes
Vaccine development
Properties of good candidate: Organism – causes significant illness Organism – 1 serotype Organism – no oncogenic potential Antibodies – block infection / systemic
spread Vaccine – heat stable
Success of immunization program
Composition of vaccine Life-long immunity Administration
TimingSiteConditions
Immunization - ? When Birth - Hep B Childhood - DTP, Polio, Hep B (2,4,6/12),
Hib (2,4,12), MMR (12/12), DT (15 -19yrs)
Adult - Boosters, 50yrs – DT(unless booster <10 yrs)
Travellers - Yellow fever, Typhoid Non-immune ♀ - MMR Risky lifestyle - Hep B, Heb A Aboriginal & >50yrs – Influenza (yearly),
or non-Abor & > 65 yrs - Pneumococcus (5-yearly)
Standard vaccination schedule
For footnotes, see: http://www.dh.sa.gov.au/pehs/Immunisation/aust-vacc-schedule-web.pdf
From: http://www.dh.sa.gov.au/pehs/communicable-diseases-index.htm
Recommended Childhood and Adolescent Immunization Schedule
Other target groups
From: Vaccine brochure, SmithKline Beecham
Challenges Predicting the protective ags
e.g., Influenza (haemagglutinin & neuraminidase variants)
Not knowing the virulence determinantse.g., Tuberculosis
Antigenic variation Promoting T-cell stimulation
Vaccine Safety – New Challenges…
1.More vaccines to oversee
2.Investment not kept up with demands
3.Benefits “invisible” as
diseases disappear
4.Real and perceived risks of vaccine more apparent
5.Public trust at stake
Chemoprophylaxis
Chemoprophylaxis as primary prevention
refers to the use of drugs or biologics taken
by asymptomatic persons to reduce the risk
of developing a disease.
The use of chemoprophylaxis is limited primarily by two factors:
1.All medications have the potential to cause side effects. In general, chemoprophylaxis should be initiated only when the benefits of treatment outweigh the risks.
2.The cost associated with chemoprophylaxis may be prohibitive, particularly when the cost of treatment is high or the incidence of the target disease is low. Many forms of chemoprophylaxis are therefore not cost-effective.
Thank Thank youyou !!