Published on

  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide


  1. 1. INTRODUCTION TO CHEMICAL PATHOLOGY Prof. David Marais 6.33 Falmouth Building UCT Health Science Faculty & NHLS Anzio Rd, Observatory, 7925, South Africa Ms Farhana Hassan - Telephone O21 4066192 UCT MBChB Semester 3 Language of Medicine Wednesday 16th January 2013, 09:00-10:00 New Learning Centre
  2. 2. Aqenda Chemical Pathology Division of Chemical Pathology Chemical Pathology Course2 lnvestigations Methods lnterpretation lmplications3 Chemical Pathology and Medical Practice Systems approach and problems
  3. 3. Definition of Chemical PatholoqvSYNONYMS ClinicalBiochemistry,ClinicalChemistry Pathologic Biochemistry (Metabolic Medicine)ETYMOLOGY Pathology: knowledge & study of disease Chemistry: knowledge and study of composition and properties and reactions of substances; Biochemistry: chemistry pertaining to life Anatomical Pathology: macro- & microscopic apearance Medical Microbiology: disease from microorganisms Forensic Pathology: causes of death, natural/criminal
  4. 4. FORMAL DEFINITION OF CHEMICAL PATHOLOGYA discipline in the Health Sciences concerned with the description of the(bio)chemical constitution of humans evidenced by samples during humanHealth and Disease, in relation to environmental or genetic factors ormetabolic stress. The changes vary in scope and degree, signifying successof homeostasis and prognosis. The findings are used in the management ofpatients, in detecting unfavourable changes in health ahead of disease so asto anticipate and avoid or ameliorate disease, and to gain insight into themechanisms of disease. Like other disciplines in healthcare thecommitment is to the patient care.ln the modern era places more reliance on objective description of disease;in 75% of medical diagnoses a laboratory test is required. This disciplinerequires interaction with clinical practitioners (contributions to special clinicsare increasing), other disciplines in pathology and (bio)chemistry as well asgenetics. Like other disciplines in Healthcare, chemical pathology not onlyprovides service but has special requirements for its practice, researches thepathophysiology of disease and diagnostic strategies whilst being aware offinancial resources. Subspecialties are emerging as technology and clinicaldemands increase
  5. 5. ORGANISATION OF CHEM PATHOLOGYCLINICAL LABORATORY SCIENCES1. Anatornical Pathology2. Chemical Pathology3. Forensic Pathology4. Haematology5. Human Genetics6. lmmunology7. lvedical Biochemistry8. lVicrobiologyCHEM ICAL PATHOLOGY(UCT & National Health Laboratory Service)Falmouth Building: Offices and Research LaboratoriesProf. Marais, Dr Blackhurst, Dr King, Ms Leisegang, Dr Mcca(hy, Mr Mohamed,Ms Solomon,Ms Ratanjee, Mr Woolley. Students.Groote Schuur Hospital C17: Clinical Service LaboratoryDr Haarburger, Dr King, Dr Omar, Dr Vreede. Dr Fortgens. Registrars.Red Cross Hospital ICH: Clinical Service Laboratory, Metabolic DisordersDr G vd Watt
  6. 6. CHEMICAL PATHOLOGY COURSE. Lectures, tutorials, patientbased problemsa Reference books, in-house notes. Principles & Concepts > facts. Scientific vs Clinical Approach (assumptions, general experience). Emphasise Diagnosis & Disorders rather than Chemistry. Read & Understand, distill to principles and vital facts. Revise anatomy biochemistry, chemistry, physiology
  7. 7. STUDY MATERIALMarshall and Bangert. Clinical Chemistry,6th ed. Published in 2008 by Elsevier - CHEMICALISBNl 0:0-7234-3455-7 PATHOLOGY I,TiCTI]RE NOTES BJ. Baynes & Marek Dominicza k MedicalBiochemistry, Mosby 2nd Ed. 2005Paula Yurkanis Bruice. Essential OrganicChemistry, Pearson lnternational Edition or2nd Edition, Pearson.Silberberg, (McGraw Hill) Chemistry. TheMolecular Nature of Matter and Change 3rd,4th or 5th edition, Mccraw HillOther Text Books. JournalsEspecially reviewslnternet searchDiscussions w
  8. 8. CHEMICAL PATHOLOGY SERVICEIN DICATIONSDIAGNOSIS: Differentialdiagnosis(chestpain)SCREEN: Disorders without much clinical manifestation (thyroid)MON ITOR: Response to treatment (hypokalaemia, diabetes)PROGNOSIS: Susceptibility to disease or complications (cholesterol)Key tests and Related tests in context(heart failure electrolytes, renal function, thiamine deficiency)SAM PLESBlood (venous/arterial), serum or plasma. Phlebotomists.U rine (dipstick or test tube analysis)Stool (occult blood, fat malabsorption by stool collection)CSF (glucose, protein)Effusions (protein)
  9. 9. SAMPLE ANALYSISCONSENT Explanation. Verbal consent unless invasive.PREPARATION Fasting,provocativetests.TIMING Diurnal rhythms.PRESERVATION Appropriateforanalysis Blood: Heparin or EDTA anticoag, NaF stops glycolysis Gases escape. Gln degradation to NH3 Urine: toluene or azide to prevent bacterial growth acidify for Mg, Ca, alkalinise for urateTECHNIQUE Venesection, etc. Stasis, haemolysis, bleed into...LABELLING Medicolegal ! Leave sample visisble, tube managableINFORMATION Report in relation to result, associated testsRECEPTION On time for lab service !COST Limit number. Preliminary test before additional.PROBLEMSPre-pre-analytical Preparation,posture,technique,formsPre-Analytical Transport, separation, aliquots, 2nd container & storeAnalytical Lab quality control.PostAnalytical Report and lnterpretation. Delay to attention.
  10. 10. METHODSManual or Automated Analysis.Analyte in matrix, interfering substances.lnspection - turbidity, lipaemia, haemolysis, colour, odour,COLORIMETR ICChemical reaction coupled to colour product, direcuindirectShort times, inexpensive, automatable, not very sensitive (mmol/L to FimoUL)U rea, creatinine, albuminFLU OR IMETRICMolecule or product responds to Excitation l, Emission.l.Not as quantitative but more sensitive (pmol/L to nmol/L).Manual, seldom in routine labs.ION SENSE ELECTRODESSelective permeability to ion changes.lnexpensive, rapid, automatable, measures unbound ions.H. for pH, Na., Ca..
  11. 11. METHODSENZYMATIC ASSAYSEnzyme specific for substrate yields product that can yield indicator orcofactor can indicate reactionLactate dehydrogenase uses NAD and generates NADH (UV absorbance)Lactate + NAD. +pyruvate+NADH +H.Concentration: molar extinction coefficient, standardsActivity: moles/time (units) relate to volume; for enzyme description.IMMU O-ASSAYS NAntibodies (Ab) are highly specific to epitopes on proteinAnalyte = antigen (Ag). Can be radio labelled and added to reaction (Ag*)Very sensitive, specific, some automation, costly to produce Ag and AbCompetitive assay: add Ag*, mix with AgAdd specific antibody (Ab) to bind Ag and/or Ag* and form complexAnalyse radio-activity in complexNo Ag means only Ag* binds and radioactivity is highLarge amount Ag successfully competes against Ag*, counts are low
  12. 12. METHODSELECTROPHORES ISProteins in buffer (sustains charge) will migrate (to anode).Agarose migration more complex, acrylamide by sizeStain, patterns: monoclonal lg, lsoenzymesRelatively inexpensive, sensitiveCH ROMATOG RAPH YSeparation between mobile and stationary phasesThin Layer Chromatography (TLC): simple, low cost, time, qualitativelon Exchange Chromatography: amino acidsGas Chromatography (volatile by derivative): organic acids, sterols, fatty acidsDNAPolymerase chain reaction (PCR); amplifies DNA (blood, buccal)Generally for specific mutations by several techniquesBiochemical phenotype similar from different genes, also polymorphismsFounder effects more cost-effective
  13. 13. INTERPRETATIONIDENTITY Ensure correct sample, timeCONTEXT Symptoms,signs,treatment,differentialdiagnosis Can assay assist in solving problem ? Pitfalls in interpretation (T4 & TSH on treatment)UNITS Reference range (age, gender, ...) Report in Sl vs other units. (TC 5.18 mmo/L = 200m9/dL) 1 mole = atomic (molecular) mass in grammes. (Avogadros Nr) NaCl: 23 da + 35 da = 58 da. Thus 589 in 1L is 1 mol/L Plasma concentration of Na. is -140 mmol/L "Physiologic saline" is 0.99/dL or 155mmol/L (31omosm/L) mmol/L Na., K., Ca.., M9.., urea, glucose, triglyceride, cholesterol pmol/L creatinine, iron, albumin (-600, or 409/L) nmol/L cortisol (-500), H. (40, or pH= 7.40), pmol/LACTH (50)
  14. 14. REF. RANGES FOR COMMON ANALYTES AMLYTE BEFERNCE UNIT RANGF ACI}BASE PH 7,36 7,41 pc02 ,1,5 6.1 Std Bicaftonale 22 -26 2,51o +2,5 il) 10,0 16,0 soDtUM 135- i45 POTASSIT]M 3,5 5,0 cHtoRtoF s7, t07 CAI CIUM 2,1 2,6 1,6 CBEATININE rmoul sFBUM OSMOIAI tfY 275 - X7 mo!1ig GTUCOSE tfasting) 3,9 6,l
  15. 15. STATISTICSDESCRIPTIVE Mean (avg) of observations (>) = ( L / n) {NB: n-1 for sample) Median (midway in observations) Variance=r(r_obs), Std deviation = ., Variance Std error of mean = StdDev / (., n) CV=StdDev/x Reference lnterval (normal ranoe): aoe. oender. socio-economic. oenes Generally >120 samples, well collected and analysed Centiles along range, lowest end is 1 and highest 100 Precision = closeness of repeated observations Accuracy = conformance with exact standard Sensitivity (%) = proportion with disease who test +ve Specificity (%) = proportion without disease who test -veCHAN GES Cvtotd of parameter relates to CV""""y & Cvbiol TC: Cvbior 5% and -Cv""""r 3% CV,*",= [(5)+(3)]= [34] =5.8 Thus on one repeat test require a change of > 11o/o
  16. 16. IMPLICATIONS OF INVESTIGATIONINSIGHT Need for test, implications for management. Confidentiality. lnformed consent for H lV disease. Gate-keeping of requests.U RGEN CY Relates to clinical decision making and cost Turn-Around-Time in lab is geared to this. Critical values are generally reported to Dr (N B contact!) Emergency: treat hypoglycaemia regardlessDOCU MENT Sending and Receiving Response to result
  17. 17. COMMON CLINICAL SETTINGS FOR INVESTIGATION Acid/base disturbances GIT disturbances acidosis/alkalosis diarrhoea respi ratory/m etabolic malabsorption Water and electrolyte disturbances pancreatitis overhydration & dehydration malignancy hypematraemia & hyponatraemia Endocrine disease hyperkalaemia & hypokalaemia diabetes Calcirm and phosphate disorders thyroid bone disease parathyroid endocrine disorders Metabolic disease Carbolrydrate homeostasis u ric acid (gout) diabetes and hypoglycaemia iron metabolism Liver dysfunction dyslipidaemias hepatitis-cirrhosis€ilu re inherited metabolic disease metabolic disorders nutritional (vitamins) jaundice (bili,transaminase,alk phos) Neoplastic disease Kidney dysfunction tumor markers (PSA, CEA) acute vs chronic failure protein (myeloma) nephrotic syndrome Toxicology metabolic disorders paracetamol Heart disease aspirin,organophosphate, ... acute myocardial infarction (CK) alcohol Fe metabolism, thiamine, ...
  18. 18. CONCLUSIONS ABOUT CHEM PATHOLOGY1. Vital for diagnosis & management of many disorders and thus has serious responsibilities in healthcare2. Appropriate investigation for patient requires good clinical assessment and careful consideration of tests (likelihood, differential, cost)3. Responsibility of requesting doctor to ensure results are applied4. Must be understood and be related to anatomy, physiology, chemistry, biochemistry, pathology, microbiology, pharmacology, ...and all else!5. Application is not restricted to laboratories but open to all medical practitioners as sideroom investigations (urine dipstick) and pointof- care testing.6. ls a fascinating discipline which will still improve our insights into disease, its diagnosis and its treatment in future.