introduction to clinical biochemistry - slides

7/25/2019 Introduction to Clinical biochemistry - Slides

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AUTOMATION IN

CLINICAL

BIOCHEMISTRYCLINICAL

BIOCHEMICALANALYSES OF

PROTEINS, PLASMAPROTEIN SPECTRUM


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Introduction to Clinicl!ioc"#$i%tr&

CLINICAL BIOCHEMISTRY(also known asclinicchemistryorchemical pathology)is the laborservice absolutely essential for medical practice obranch of laboratory medicine in which chemical biochemical methods are applied to the study of

The results of the biochemical investigations carin a clinical chemistry laboratory will help the clinto determine the diseases (diagnosis) and for follthe treatment/recovery from the illness (prognosi


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T"# u%# o' !ioc"#$icl t#%t%( Biochemical investigations are involved in every branch

clinical medicine.The results of biochemical tests may be of use in: diagnosis and in the monitoring of treatment. screening for disease or in assesing the prognosis.

reseach into the biochemical basis of disease clinical trials of new drugs Biochemical investigations hold the key for the diagnosi

prognosis of diabetes mellitus !aundice myocardial infagout pancreatitis rickets cancers acid-base imbalance"uccessful medical practice is unimaginable without theof clinical biochemistry laboratory.


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#n general biochemical tests can be broadly divided into twgroups: #n discretionary or selective requesting,the tests are

out on the basis of an individual patient$s clinical situation.for discretionary re%uesting has been put admirably (&she

'. +hy do # re%uest this test, . +hat will # look for in the result,

. #f # nd what # am looking for will it a0ect my diagnosis, *. 1ow will this investigation a0ect my management of the . +ill this investigation ultimately benet the patient, #n contrast %cr##nin) t#%t%are used to search for diseas

there being any necessary clinical indication that disease i


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T#%t %#l#ction 'or t"# *ur*o%#% o' di%cr#tiot#%tin)Ct#)or& E+$*l#To conr$ di)no%i% Pl%$ -'r## T/ nd

-t"&roid0%ti$ultin)"or$on#, TSH/ in %u%*#ct#d"&*#rt"&roidi%$

To id di1#r#ntil di)no%i% To di%tin)ui%" !#t2##ndi1#r#nt 'or$% o' 3undic#

To r#n# di)no%i% U%# o' ACTH to locli4#Cu%"in)5% %&ndro$#

To %%#% t"# %#6#rit& o'di%#%#

Pl%$ -cr#tinin#/ or -ur#/in r#nl di%#%#

To $onitor *ro)r#%% Pl%$ -)luco%#/ to 'ollo2 o'*ti#nt% 2it" di!#t#%$#llitu%

To d#t#ct co$*liction% or%id# #1#ct%

ALT $#%ur#$#nt% in*ti#nt% tr#t#d 2it""#*toto+ic dru)

To $onitor t"#r*& Pl%$ dru) conc#ntrtion in*ti#nt% tr#t#d 2it"

nti#*il#*tic dru)%


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T!l# 7. E+$*l#% o' t#%t% u%#d in c%#0n*ro)r$$#%.Pro)r$$#% to d#t#ct

di%#%#% inC"#$icl in6#%ti)tion%

N#ont#%(P9A -*"#n&l:#tonuri/ S#ru$ ;*"#n&llnin#DU. M

)#n#rt#d 2it"in t"# L!ortor& occur t t"# R#c#*tion % r#%ult o' $o' %$*l#% 2it"in t"# L!ortor&


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COLLECTION OF BLOOD( Venousbloodis most commonly used for a ma!ority

biochemical investigations. #t can be drawn from anyprominent vein (usually from a vein on the front of the

Capillary blood (GF. ml) obtained from a nger or tless fre%uently employed.

Arterial blood (usually drawn under local anesthesia

for blood gas determinations. Pr#cution% 'or !lood coll#ction (=se of sterile (p

disposable) needles and syringes cleaning of patientsblood collection in clean and dry vials/tubes are someimportant precautions.


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Introduction to Clinicl!ioc"#$i%tr& Bioc"#$icl in6#%ti)tion% cn !# *#r'or$#don o' !lood %*#ci$#n%I whole blood plasma serum andblood cells. The selection of the specimen depends on thparameter to be estimated.

7. Whole blood(usually mi3ed with an anticoagulant) ifor the estimation of hemoglobin carbo3yhemoglobin pglucose urea non-protein nitrogen pyruvate lactate aetc. (@ote : for glucose determination plasma is prefererecent years).

. Pl%$,obtained by centrifuging the whole blood cowith an anticoagulant is employed for the parametersJbrinogen glucose bicarbonate chloride ascorbic acid


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. S#ru$is the supernatant 5uid that can be collafter centrifuging the clotted blood. #t is the mostfre%uently used specimen in the clinical biochemislaboratory. The parameters estimated in serum incproteins (albumin/globulins) creatinine bilirubincholesterol uric acid electroylets (@aC DC >l-) e

(&9T &"T 981 >D &9 &> amylase lipase) andvitamins.

. R#d !lood c#ll%are employed for the determiof abnormal hemoglobins glucose K-phosphatedehydrogenase pyruvate kinase etc.


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Introduction to Clinicl!ioc"#$i%tr& Coll#ction nd *r#%#r6tion o' !lood %*#ci$#n%

9ack of thought before collecting specimens or carelessness in colleadversely a0ect the interpretation or impair the validity of the testson the specimens. "ome factors to consider include the following:

7.iet8ietary constituents may alter the concentrations of analytsignicantly (e.g. plasma LglucoseM and LtriglycerideM are a0ected bcarbohydrate and fat-containing meals respectively).

.rugs4any drugs in5uence the chemical composition of blood. e0ects of drug treatment for e3ample antiepileptic drugs have to

into account when interpreting test results. 8etailsof relevant drugmust be given when re%uesting chemical analyses especially whento3icological investigations are to be performed.

.iurnal variation.The concentrations of many substances in bconsiderably at di0erent times of day (e.g. cortisol). "pecimens for analyses must be collected at the times specied by the laboratorymay be no reference ranges relating to their concentrations in blootimes


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Introduction to Clinicl!ioc"#$i%tr& Cr# 2"#n coll#ction !lood %*#ci$#n%

The posture of the patient the choice of skin-cleansing athe selection of a suitable vien (or other source) are the pfactors to consider before proceeding to collect each spe

7. !he s"in must be cleanover the site for collecting specimen. 1owever it must be remembered that alconolmethylated spirits can cause haemolysis and that their u

clearly to be avoided if blood LethanolM is to be determine . #imbs into $hich intravenous infusionsare being

must not be selected as the site of venepuncture unless care is taken. The needle or cannula must rst be thorou5ushed out with blood to avoid dilution of the specimen winfusion 5uid.


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Introduction to Clinicl!ioc"#$i%tr& . Venepuncture technique should be standardisedas fa

possible to enable closer comparison of successive results on p .Venous blood specimens should be obtained $ith min

stasisrolonged stasis can markedly raise the concentrations proteins and other non-di0usible substances (e.g. protein-bounsubstances). #t is advisable to release the tourni%uet before witthe sample of blood.

.%osture should be standardised if possible+hen a patposture changes from lying to standing there may be an increa

much as 'N in the concentration of plasma proteins or proteinconstituents due to redistribution of 5uid in the e3tracellular sp . &aemolysis should be avoided,since it renders specime

unsuitable for plasma K+,magnesium and many protein and enactivity measurements.

J.'nfection haard 1igh-risk specimens re%uire special carecollection and this danger must be clearly indicated on the re%


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Introduction to Clinicl!ioc"#$i%tr& Cr# o' !lood %*#ci$#n% 't#r coll#ction

Blood specimens should be transported to the laborasoon as possible after collection. "pecial arrangemenneeded for some specimens (e.g. for acid-basemeasurements or unstable hormones) because of thof stability. 4ost other analytes are stable for at leastwhole blood or longer if plasma or serum is rst sepa

from the cells. &s a rule whole blood specimens for canalysis must not be stored in a refrigerator,since iopumps that maintain electrolyte gradients across themembrane are inactiveatlow temperatures. >onverseparated serum or plasma is best refrigerated to mchemical changes or bacterial growth.


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Introduction to Clinicl!ioc"#$i%tr& "everal changes occur in whole blood specimens followin

collection. The commoner and more important changes thpriorto the separation of plasma or serum from the cells

'. ;lucose is converted to lactate: this processisinhibite5uorideE

. "everal substances pass through the erythrocyte memmay be added in signicant amounts to plasma as a resucell destruction insuOcient to cause detectable haemolys

63amples include DC

and lactate dehydrogenaseE . 9oss of >Poccurs since the co of blood is much hig

in airE *. lasma LphosphateM increases due to hydrolysis of orga

phosphates in the red cellsE . 9abile plasma enymes lose their activity.

introduction to clinical biochemistry - slides

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