INTRODUCTION TO LABORATORY MEDICINE
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 profilesLiver and renal panelsBone metabolismLipid chemistry
Special chemistryCardiovascular markersTumour markersNutritional markersCalculi
Immunology and ImmunodiagnosticsDrug monitoringUrine and serum proteinsAutoimmune disease testingEndocrinology testsFertility testing
Point-of-Care TestingCardiac markersGlucose monitoring programBlood gases and metabolitesRoutine chemistry panelsRoutine urinalysis and pregnancy screeningCoagulationComplete Blood Counts Urine toxicology screening
Laboratory Hematology Routine and special hematology
Hemoglobinopathy studiesSpecial stains
HematopathologyBone marrow consultations and
interpretive report Flow cytometry
CD 34 (stem cell) enumerationCD4/CD8 monitoringLeukemia/lymphoma immunophenotypingPNH
Special coagulationCoagulation profiles, screening and factors
and inhibitorsPlatelet studiesThrombophilia testing
MicrobiologyBacterial culture and sensitivitiesBlood culturesMolecular typing of organismsViral detection methodologiesHIV viral load -public health lab accredited
site for viral loadChlamydia 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 Ramnik Sood.
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 BANKVery 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 REQUESTSTAT Performed immedi
ately 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 VALUESNot fixed for allShould consider:
Age Sex Pregnancy Diurnal Variation Race Blood type
ROUTINE EXAMINATIONSROUTINE ADMISSION TESTS
CBC, Urinalysis, FecalysisROUTINE 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 typesDangerous 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 COMPOSITIONS
COMPOSITION OF LIPOPROTEINS
Class Diameter (nm)
% protein
% cholesterol
% phospholipid
% triacylglycerol& cholesterol ester
HDL 5–15 33 30 29 4LDL 18–28 25 50 21 8IDL 25–50 18 29 22 31VLDL 30–80 10 22 18 50Chylomicrons 100-1000 <2 8 7 84
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.
LIPOPROTEIN METABOLISM
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
ECG CHANGES
CARDIAC PROFILE TEST
ENZYMES Creatinine Kinase –MB(CK-MB) Lactate Dehydrogenase(LDH 1 and 2) Aspartate Aminotransferase(AST)/Serum
Glutamate Oxaloacetate Transaminase(SGOT) Alanine Aminotransferase(ALT)/ Serum Pyruvate
Transaminase(SGPT)
LIPID PROFILE CHOLESTEROL TRIGLYCERIDE HDL LDL
PROTEINS Myoglobin Troponins
CARDIAC PROFILECardiac 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: Aspartate aminotransferase (AST) Lactate dehydrogenase (LD) Creatine Kinase (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)
CREATINE KINASE (CK)
Is a cytosolic enzyme involved in the transfer of energy in muscle metabolism
Catalyzes the reversible phosphorylation of creatine by ATP
-Is a dimer comprised of two subunits, resulting in three CK isoenzymes The B, or brain form The M, or muscle form
Three isoenzymes isolated after electrophoresis:
CK-BB (CK1) isoenzyme
Is of brain origin aand only found in the blood if the blood-brain barrier has been breached
CK-MM (CK3) isoenzyme Accounts for most of the CK activity in skeletal muscle
CK-MB (CK2) isoenzyme Has the most specificity for cardiac muscle It accounts for only 3-20% of total CK activity in the heart Is a valuable tool for the diagnosis of AMI because of its
relatively high specificity for cardiac injury Established as the benchmark and gold standard for
other cardiac markers
Considerations in CK assays
CK is light sensitive and anticoagulants like
oxalates and fluorides inhibit its action CK in serum is very unstable and rapidly loss
during storage Stored specimens are not used since it
contains cellular products and intermediate like adenylate kinase, ATP and G-6-Phosphate which affect the assay
Exercise and intramuscular injections causes CK elevations
Clinical Significance -In myocardial infarction, CK will rise 4-6
hours after the onset of pain -Peaks at 18-30 hours and returns to normal
on the third day -CK is the most specific indicator for
myocardial infarction (MI)
Raised levels of CK Progressive muscular dystrophy Polymyositis Acute psychosis Alcoholic myopathy Delirium tremens Hypothyroidism Malignant hyperthermia Acute cerebrovascular disease Trichinosis and dermatomyositis
Normal Value: a. Male – 25-90 IU/mL b. Female – 10-70 IU/mL
CHOLESTEROL
Normal values: range varies according to age Total Cholesterol: 150-250mg% Cholesterol esters: 60-75% of the total
cholesterol
CHOLESTEROL IS ADVISED IF YOU have been diagnosed with coronary heart disease, stroke or mini-stroke (TIA) or peripheral arterial disease (PAD) are over 40 have a family history of early cardiovascular disease have a close family member with cholesterol-related condition are overweight have high blood pressure, diabetes or a health condition that can increase cholesterol levels, such as an underactive thyroid
FACTORS LEADING TO RAISED CHOLESTEROL an unhealthy diet: some foods already contain
cholesterol (known as dietary cholesterol) but it is the amount of saturated fat in your diet which is more important
smoking: a chemical found in cigarettes called acrolein stops HDL from transporting LDL to the liver, leading to narrowing of the arteries (atherosclerosis)
having diabetes or high blood pressure(hypertension) having a family history of stroke or heart disease There is also an inherited condition known as familial
hypercholesterolaemia (FH). This can cause high cholesterol even in someone who eats healthy diet.
TRIGLYCERIDES Ester derived from glycerol and three fatty acids. Main lipids in the blood and important energy substrate. Insoluble in water. Hypertriglyceridemia
Not an important risk facotr for coronary artery disease. It can cause pancreatitis when severe.
Both hypertriglyceridemia and hypercholesterolemia are associated with various types of cutaneous fat deposition and xanthomatas.
Hypertension Very common clinical problem. Usually essential type
meaning that have no identifiable cause. Investigations for treatable causes like endocrine is
necessary.
HYPERLIPIDEMIAS
LIVER
Anatomy of liver
LIVER HISTOLOGY
I. TESTS BASED ON EXCRETORY FUNCTIONS
LABORATORY RESULTS
II. TESTS DUE TO DETOXIFICATION
TESTS B/O SYNTHETIC FUNCTION
Liver is the main source of synthesis of Plasma proteins
Albumin Globulin
Blood clotting factors Prothrombin Factors V, VII, and X
SERUM ALBUMIN 3.5- 5.5 gm/dl
SERUM GLOBULIN 2 -3.5 gm/dl
TOTAL PROTEINS 6-8 gm/dl
Albumin/ Globulin ratio 1.2:1 – 2.5: 1
Prothrombin time
TESTS B/O METABOLIC FUNCTIONS
SERUM TRANSAMINASES SERUM ALKALINE PHOSPHATASES
REFERENCE RANGE ALT ( upto 42 U/L) AST (0-37 U/L) ALP (65-306 U/L) raised in obstructive
jaundice.
OTHER ENZYMES GGT (11-60 u/l) 5- NUCLEOTIDASE (2-17u/L) LDH (180-360 u/l)
pathogenesisDifferent cells have different enzymes inside them,
depending on the function of the cell. Liver cells happen to have lots of AST, ALT, and GGTP inside them. When cells die or are damaged, the enzymes leak out causing the blood level of these enzymes to rise; that is why the levels of these enzymes in the blood are considered good indicators of liver cell damage. ALT is more specific for liver disease than AST because AST is found in more types of cell (e.g. heart, intestine, muscle). The AST, for instance, will rise after a heart attack or bruised kidney. GGTP and AP are said to be more specific for evaluating biliary disease since they are made in bile duct cells. In liver disease caused by excess alcohol ingestion, the AST tends to exceed the ALT, while the reverse is true to for viral hepatitis. However, this particular generalization is often wrong. There are several things to remember:
GGT (OR GGTP) Gamma Glutamyl Transpeptidase. This
enzyme level is elevated in case of liver disorders. In contrast to the alkaline phosphatase, the GGT tends not to be elevated in diseases of bone, placenta, or intestine
PROTHROMBIN TIME
good correlation between abnormalities in prothrombin time and the degree of liver dysfunction.
Expressed in seconds and compared to a normal control patient's blood
SPECIALIZED TESTS serum iron, the percent of iron saturated in blood, the storage protein ferritin for hemochromatosis. accumulation of copper in the liver in wilson
disease.
RENAL PANEL
Creatinine Calcium Sodium Chloride Carbon dioxide Albumin Blood urea nitrogen (BUN) Protein Phosphorus Glucose Potassium
Glucose Potassium Phosphorous Sodium Albumin BUN Creatinine BUN/Creatinine Ratio Calcium Chloride Carbon Dioxide (CO2), Total
BONE METABOLISM Bone is constantly remodelling Bone resorption= bone formation Why remodelling is necessary?
To withstand changing environment To cope with workload To repair damage caused by recurrent
microtraumasBONE METABOLISMOsteoclasts and OsteoblastsOsteocytes\Encased osteoblasts which are connected to each
other by long cellular processes forming a network connected by gap junctions.