1.introduction To Chemical Pathology 4u3i42

Introduction to Chemical Pathology Intake 32 Dr I D Siriwardhana Senior Lecturer in Pathology

What are you going to learn from this lecture? • What is Chemical Pathology? – The scope

• What you should learn about Chemical Pathology? – From Clinical appointments – Clinical Pathology appointment

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What is Chemical Pathology? • Is the area of Pathology that is generally concerned with analysis of body fluids. • Other names: – Clinical Biochemistry – Clinical Chemistry • All biochemical tests are done in the Biochemistry/Chemical Pathology () section of the Pathology Laboratory. 3

Why are biochemical tests requested? • For diagnosis of disease • To get prognostic information – to predict disease severity/outcome • To monitor the effects of treatment • To screen for subclinical disease

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What are the different types of samples sent to Chemical Pathology labs? • • • • • • •

Serum Plasma Whole blood Urine CSF Peritoneal/pleural fluid t/cyst aspirates

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A modern Chemical Pathology laboratory

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The scope of Chemical Pathology • General or routine biochemistry • Endocrinology - the study of hormones • Pharmacology or Toxicology - the study of drugs

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General/Routine Biochemical Tests • • • • • • •

Plasma glucose Blood urea Serum electrolytes Serum creatinine Total protein and albumin Serum bilirubin Serum cholesterol 8

General/Routine Biochemistry – Enzyme assays

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Aspartate Transaminase (AST) Alanine Transaminase (ALT) Alkaline Phosphatase Amylase Creatine Kinase Gamma Glutamyl Transferase 9

General/Routine Biochemical Tests • • • •

Serum Calcium Serum Phosphate Arterial Blood Gas analysis Urine Analysis – Urine full report

• CSF analysis – CSF full report

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Generation of biochemical lab reports – whose responsibility? Patient

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Generation of biochemical lab reports – whose responsibility? Patient

Doctors Nursing Officers Attendants Labourers

Medical Laboratory Technologists/ Scientists

Medical Officers Registrars in Pathology Chemical Pathologist 12

If you are to become an efficient Medical Officer • • • • •

What should you learn? When to request? – Test indications What to request? – Rational selection of tests How to prepare patients How to collect samples and principles of transport • Interpretation of biochemical data 13

Test requests

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Pathology Request – TH Karapitiya

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Sample collection devices

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Proper sample collection

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Interpretation of biochemical data • Need to be aware of possible errors • Errors can occur in 3 stages – Preanalytical – Analytical – Post analytical

• Errors in preanalytical phase – Patient preparation – Sample collection and transport 18

Preanalytical Errors • Some Examples – Collection of blood proximal to an intravenous drip – Haemolysed samples – Collection of blood for serum electrolytes to an EDTA bottle

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What you should learn - Knowledge • Indications • Appropriate selection of tests based on pathological changes • Principles of sample collection and transport • How to interpret general biochemical test reports 20

Where to find knowledge? • From the laboratory staff/ clinical staff /teachers in Pathology • Text books in Clinical Chemistry – Clinical Chemistry by William J. Marshall – 8th edition • Lab Tests online (web site)

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What you should learn - Skills • Writing proper requests • Correct venipuncture technique under aseptic conditions • Collection to appropriate container and labeling • Handling of patient specimens • Observe and perform under supervision

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What you should learn -Attitudes • • • •

Patient education Consent for obtaining samples Minimize pain and number of invasive tests Explain test results in a manner which they can understand

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Learning Outcomes • Describe the scope & clinical significance of tests in Chemical Pathology • Describe the role of the requesting doctor in the preanalytical and the post-analytical phases • Describe the principles of sample collection and transport requirements for common general biochemical and specialized biochemical investigations • Be able to interpret common biochemical test reports 25