Definition Laboratory medicine a specialty in which pathologists provide testing of patient samples (usually blood or urine) in several different areas. • Determination of the level of enzymes in blood in case of heart attack or • Level of glucose (sugar) in the blood of a patient with diabetes. • The presence of bacteria and other microorganisms. • Blood cells studies for various types of anemias
Course objectives • application of basic science to those clinical disciplines practiced by the medical laboratory scientist. • the scope of Laboratory Medicine, and of its potential applications. • How to analyze various samples under certain circumstances.
Course contents • Clinical Biochemistry • Cardiac profiles • Liver and renal panels • Bone metabolism • Lipid chemistry • Special chemistry • Cardiovascular markers • Tumour markers • Nutritional markers • Calculi
Immunology and Immunodiagnostics • Drug monitoring • Urine and serum proteins • Autoimmune disease testing • Endocrinology tests • Fertility testing • Point-of-Care Testing • Cardiac markers • Glucose monitoring program • Blood gases and metabolites • Routine chemistry panels • Routine urinalysis and pregnancy screening • Coagulation • Complete Blood Counts • Urine toxicology screening
Laboratory Hematology • Routine and special hematology • Hemoglobinopathy studies • Special stains • Hematopathology • Bone marrow consultations and interpretive report • Flow cytometry • CD 34 (stem cell) enumeration • CD4/CD8 monitoring • Leukemia/lymphoma immunophenotyping • PNH
Special coagulation • Coagulation profiles, screening and factors and inhibitors • Platelet studies • Thrombophilia testing • Microbiology • Bacterial culture and sensitivities • Blood cultures • Molecular typing of organisms • Viral detection methodologies • HIV viral load -public health lab accredited site for viral load • Chlamydia detection
Infection control • Reference centre for medical microbiology and infectious diseases • Detection and typing of epidemiologically significant organisms • Serology • Clostridium difficile toxin testing • Wide range of viral and non-viral serologies • Molecular Diagnostic Testing • Wide range of molecular testing for viral and bacterial agents • Mycology • Fungus detection • Cells/tissues/organ donor testing • Blood Bank/Donor Center • Concepts of immunohematology and histocompatibility • Blood transfusion services and quality assurance • Blood donation and storage of blood • Blood grouping • Compatibility testing
Recommended Books Textbook: District laboratory practice in tropical countries by Monica Cheesbrough. Clinical chemistry by William J Marshall. Reference books: Medical Laboratory technology by RamnikSood.
Reasons for ordering tests • Aid in diagnosis • Confirm diagnosis • Evaluate prognosis • Monitor therapy • Screen for a disease
Sections of the Laboratory CLINICAL PATHOLOGY 1. Clinical Chemistry • BUN • Cholesterol • FBS 2. Clinical Microscopy • Analysis of body fluids • Urin analysis • Fecal anaysis • Semen analysis 3. Microbiology • Cultures (sputum, blood, urine) 4. Hematology Biggest section Includes CBC,coagulation, PT, PTT
Blood bank Very critical section Bec. May have errors • Blood typing • Cross match • AB • Identification Goes hand in hand with serology and immunology Tests done for • MALARIA • SYPHILIS • HIV Serology/Immunology • Cardiac and thyroid fxntest II. ANATOMY PATHOLOGY Histopathology Submission of tissues for tests
Laboratory services • Laboratory investigations of the patient. • Laboratory aspects of detection and prevention of diseases. • Request • System of analysis • System for interpretation of results and timely advice relevant to the urgency of the clinical problem
Functions of a hospital laboratory • To meet the request for laboratory investigations by maintaining adequate diagnostic facilities. • To arrange for laboratory investigations from referral laboratories if not available in the premises. • To provide professional advice on the management of the patient. • To monitor individual patients. • To provide laboratory facilities for research projects under taken by clinicians. • To collaborate in development, study and control of new methods of treatment.
To understand applied research on pathology related problems. • To arrange for the training of the medical and paramedical staff.
Nature of Request STAT • Performed immediately and by itself. • Run control and standard • 20-50% More expensive • TAT is shortened • Request is needed Today • Confusing • Performed as soon as possible, given priority • Based on “running time” Routine • Done with the batch • Wait for TAT stated by laboratory
Values REFERENCE VALUES • Better term than “normal value” • Pulled value, usually 95%of population • Vary in diff. hospitals but not that far SIGNIFICANT VALUES • Clinical decision should be made if higher or lower than reference value • Usually when 2x to 3x
CRITICAL VALUES • Needs immediate attention • “panic values” • Should call physician • Patient is at risk
Reference Values Not fixed for all Should consider: • Age • Sex • Pregnancy • Diurnal Variation • Race • Blood type
Routine Examinations ROUTINE ADMISSION TESTS CBC, Urinalysis, Fecalysis ROUTINE CHEMISTRIES BUN, Creatinine, Glucose, Uric Acid, Cholesterol Sometimes triglycerides
Basic lab equipments • The Light Microscope. • Colorimeters and photometers • Water bath • Laboratory centrifuge • Balance • Cold incubators refrigerators • pH meters • Mixers • Ovens • De-ionizers • Safety cabinets. • Glassware and plasticware
Sampling • Pathologist should try to answer the question which is imposed by the clinician. • Correct specimen for requested test with necessary information so that right test is carried out And result is delivered to the requesting clinician with the minimum of delay. • Patient identification must be correct.
Specimen types • Venous blood serum or plasma. • Arterial blood. • Capillary blood • Urine • Feces • Cerebrospinal fluid • Sputum and sliva • Tissue and cells • Aspirates (pleural fluid, ascites, joint fluid, intestinal (duodenal) fluid, pancreatic pseudocysts. • Calculi
Blood specimens • Serum • Plasma Urine specimen • Preservative may be added to prevent bacterial growth or acid may be added to stabilize metabolites. Other specimen types Dangerous specimen • Labelled as “dangerous specimen” yellow sticker. • Similar label should be attached on the request form. • HBV and HIV
Sampling errors • Blood sampling techniques • Prolonged stasis during venepuncture • Insufficient specimen • Errors in timing • Incorrect specimen container • In appropriate sampling site • Incorrect sample storage.
Lipid chemistry and cardiovascular profile • Main lipids in the blood are the triglycerides and cholesterol.(phospholipids, FFA) • These are insoluble in the water. • Transport in the blood is via lipoproteins.(protein) • 4 major classes of lipoproteins. • Chylomicrons • Very low density lipoproteins (VLDL) • Low density lipoproteins (LDL) • High density lipoproteins (HDL)
lipoproteins • Chylomicrons carry triglycerides ( dietary fat) from the intestines to the liver, to skeletal muscle, and to adipose tissue. • Very-low-density lipoproteins (VLDL) carry (newly synthesised or endogenous) triglycerides from the liver to adipose tissue and metabolized to LDL through IDL. • Intermediate-density lipoproteins (IDL) are intermediate between VLDL and LDL. They are not usually detectable in the blood. • Low-density lipoproteins (LDL) carry cholesterol from the liver to cells of the body. LDLs are sometimes referred to as the "bad cholesterol" lipoprotein. • High-density lipoproteins (HDL) collect cholesterol from the body's tissues, and take it back to the liver. HDLs are sometimes referred to as the "good cholesterol" lipoprotein.
60% of plasma cholesterol is present in LDL, 25% in HDL and small quantity in VLDL. • Lipoprotein metabolism is controlled by their protein component apolipoproteins. • Apo A-1 in HDL and Apo B-100 in LDL are very important ones. • Lipoprotein (a) in also present in human plasma. It is synthesized in the liver. • Smaller but denser than LDL. • Cholesterol esters are major lipids and it is an independent risk factor for IHD.
LDL and VLDL are associated with premature atherosclerosis. • HDL high levels are negative risk factors for IHD. • HYPERLIPIDEMIA • Coronary heart disease • Acute pancreatitis • Failure to thrive and weakness • Cataract
Endothelial dysfunction • Lpid accumulation. • Migration of inflammatory cells into the arterial wall. Atherosclerosis and plaque formation Plaque stability SCAD (asymptomatic) Chest pain at rest (angina, non ST elevation MI, STEMI)
pathophysiology • Atherosclerotic plaque, rupture and thrombus formation. • Obstruction of coronary circulation. • Necrosis of the heart tissue. • Irreversible cardiac injury if occlusion is complete for 15-20 mins. • Starts from endocardium and spreads towards epicardium. • If full thickness of myocardium is involved then it is transmural infarct.
Precipitating factors • Physical exertion • After surgical operation • Early in the morning (adrenergic activity, fibrinogen level, platelet adhesiveness is increased). • In the winter months • Emotional stress
Diagnosis of MI • Detection of rise and fall of cardiac biomarker troponinT/I with one of the following: • Symptoms of ischemia • ECG changes • Q wave
CARDIAC PROFILE TEST • ENZYMES • CreatinineKinase –MB(CK-MB) • Lactate Dehydrogenase(LDH 1 and 2) • AspartateAminotransferase(AST)/Serum Glutamate OxaloacetateTransaminase(SGOT) • AlanineAminotransferase(ALT)/ Serum PyruvateTransaminase(SGPT) • LIPID PROFILE • CHOLESTEROL • TRIGLYCERIDE • HDL • LDL
Proteins • Myoglobin • Troponins
Cardiac profile Cardiac Enzymes Cardiac Profile assesses the function of the heart’s muscle and the increased level of enzymes following a myocardial infarction. The cardiac enzymes include the following: • Aspartateaminotransferase (AST) • Lactate dehydrogenase (LD) • CreatineKinase (CK)
ASPARTATE AMINOTRANSFERASE (AST) (SGOT) found in all tissue, especially the heart, liver, and skeletal muscles it catalyzes the transfer of the amino group of aspartic acid to alpha-ketoglutaric acid to form oxaloacetic acid and glutamic acid Reaction catalyzed: Amino group Alpha-keto group Oxaloacetate & In aspartic acid In alpha-ketoglutaric acid glutamate Considerations in AST assays -Serum is the best specimen -Hemolyzed samples must be avoided -Alcohol lowers AST values -Muscle trauma like intramuscular injections, exercise, or surgical operation can significantly increase AST levels
Clinical significance • Myocardial infarction • In myocardial infarction, AST levels are usually 4-10 times the upper limit of normal • These develop within 4-6 hours after the onset of pain • Peak on the 24th – 36th hour • Usually normalize on the 4th or 5th day • Muscular dystrophy • Hepatocellular disorders • Skeletal muscle disorders • Acute pancreatitis
Increased levels of AST • Drug hepatoxicity • Pulmonary infarction • Pericarditis • Acute hepatitis • Skeletal muscle disorders
Decreased levels of AST • Pregnant women Falsely elevated results • Bilirubin • Aceto-acetatae • N-acetyl compounds • P-aminophenol • Sulfathiozole • Isoniazid • Methyldopa • L-dopa • Ascorbic acid
LACTATE DEHYDROGENASE (LDH) • Catalyzes the reversible oxidation of lactate to pyruvate • Used to indicate AMI • Is a cytoplasmic enzyme found in most cells of the body, including the heart • Not specific for the diagnosis of cardiac disease
Distribution of LD isoenzymes • LD1 and LD2 (HHHH, HHHM) • Fast moving fractions and are heat-stable • Found mostly in the myocardium and erythrocytes • Also found in the renal cortex • LD3 (HHMM) • Found in a number of tissues, predominantly in the white blood cells and brain • LD4 and LD5 (HMMM, MMMM) • Slow moving and are heat labile • Found mostly in the liver and skeletal muscle
Considerations in LD assays • Red cells contain 150 times more LDH than serum, therefore hemolysis must be avoided • LDH has its poorest stability at 0°C Clinical Significance • In myocardial infarction, LD increases 3-12 hours after the onset of pain • Peaks at 48-60 hours and remain elevated for 10-14 days • In MI, LD1 is higher than LD2, thus called “flipped” LD pattern
flipped LDH An inversion of the ratio of LD isoenzymes LD1 and LD2; LD1 is a tetramer of 4 H–heart subunits, and is the predominant cardiac LD isoenzyme; Normally the LD1 peak is less than that of the LD2, a ratio that is inverted–flipped in 80% of MIs within the first 48 hrs DiffDx. LD flips also occur in renal infarcts, hemolysis, hypothyroidism, and gastric CA
Increased levels of LD • Megaloblastic anemia • Pulmonary infarction • Granulocyte leukemia • Hodgekin’s disease • Hemolytic anemia • Infectious mononucleosis • Progressive muscular dystrophy (PMD)