INTRODUCTION TO LABORATORY MEDICINE

LIPID CHEMISTRY AND CARDIOVASCULAR PROFILE Main lipids in the blood are the triglycerides

and cholesterol. These are insoluble in the water. Transport in the blood is via lipoproteins. 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 (fat) from the intestines to

the liver, to skeletal muscle, and to adipose tissue.

Very-low-density lipoproteins (VLDL) carry (newly synthesised) triglycerides from the liver to adipose tissue.

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.

CHYLOMICRON STRUCTURE

LIPOPROTEIN METABOLISM

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

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   Reference range: < 35 U/L in male and < 31 in female

Considerations in AST assays -Serum is the best specimen-Hemolyzed samples must be avoided-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 Chronic alcohol abuse 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

Interferences

Mercury Cyanide fluoride

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 LDHAn 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 Trauma 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 and 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 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 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 cholesterol 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.

LIVER

Anatomy of liver

LIVER HISTOLOGY

FUNCTIONS OF LIVER Metabolic Synthesis Breakdown Other functions – storage of vitamin

A,D,B12,F… Excretion of waste products from

bloodstream into bile Vascular – storage of blood

SYNTHESIS Protein metabolism Synthesis of amino acids Carbohydrate metabolism Gluconeogenesis Glycogenolysis Glycogenesis Lipid metabolism Cholesterol synthesis Lipogenesis Production of coagulation factors I, II, V, VII, IX, X and XI, and

protein C, protein S and antithrombin Main site of red blood cell production Produces insulin-like growth factor 1 (IGF-1), a polypeptide

protein – anabolic effects Production of trombopoetin

BREAKDOWN Breaks down insulin and other hormones Breaks down hemoglobin Breaks down or modifies toxic substances

(methylation) → sometimes results in toxication

Converts ammonia to urea

OTHER FUNCTIONS Produces albumin, the major osmolar

component of blood serum Synthesizes angiotensinogen, the hormone

responsible for raising blood pressure when activated by renin (enzyme released when the kidney senses low blood pressure)

LIVER PROFILEThe typical Liver Profile test includes

ALT AST Alkaline Phosphatase GGTP Bilirubin Prothrombin time Protein LDL Albumin Globulin.

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.

AMINOTRANSFERASESThe normal range is 5-40 IU/L 

 ALKALINE PHOSPHATASE Sites Liver

Gallstone tumor blocking the common bile duct alcoholic liver disease drug-induced hepatitis

o Bone, placenta, and intestine. o GGT is utilized as a supplementary test

GGT (OR GGTP) (0-30 IU/L) 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

BILIRUBIN Jaundice breakdown of a substance in red blood cells

called "heme. less than 1.1 mg/dL Increased production Decreased excretionALBUMIN3.5- 5.2 g/dL  chronic liver diseaseKidney diseases (20 mg/ g of creatinine)GIT diseasesEdema and ascites.

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 PRO FILE

RENAL PANEL

Glucose BUN Creatinine Potassium Phosphorous Sodium Albumin BUN/Creatinine Ratio Calcium Chloride Carbon Dioxide (CO2), Total

GLUCOSE ( To find out the cause of renal disease. Diabetic nephropathy.

BUN (7 to 20 mg/dl)

Formed in the liver by the metabolism of the proteins.

Kidney function May be low if there is liver pathology even if

kidneys are normal

BUN/CREATININE RATIO BUN-to-creatinine ratio can help your doctor

check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.

High BUN-to-creatinine ratios occur with sudden (acute) kidney failure, which may be caused by shock or severe dehydration. A low BUN-to-creatinine ratio may be associated with a diet low in protein, a severe muscle injury called rhabdomyolysis, pregnancy, cirrhosis or syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Normal Results: 10:1 to 20:1

CREATININE (0.8 TO 1.4 MG/DL) It is a breakdown product of creatine (muscle proteine). Formed in liver and kidney. Excretion is via klidneys so level raises when kidney is diseased.

POTASSIUM(3.7 to 5.2 mEq/L) the amount of potassium in the blood High blood potassium levels may be caused by damage or injury

to the kidneysPHOSPHORUS Phosphorus is a mineral that makes up 1% of a person's total

body weight. High levels of phosphorus in blood only occur in people with

severe kidney disease or severe dysfunction of their calcium regulation.

Along with excess calcium they may calcify in the soft tissues.

SODIUM(135 TO 145 MEQ/L) High levels of sodium can increase the chance of high

blood pressure. If your total body water is low, high sodium levels may be

due to fluid loss from excessive sweating, diarrhea, use of diuretics or burns.

If your total body water is normal, high sodium levels may be due diabetes insipidus or too little of the hormone vasopressin.

If your total body water is high, high sodium levels may indicate hyperaldosteronism, Cushing syndrome, or a diet that's too high in salt or sodium bicarbonate

Low total body water and sodium levels may be due to dehydration, vomiting, diarrhea, over diuresis, or ketonuria

An increase in total body water and low sodium levels may indicate congestive heart failure, nephrotic syndrome or other kidney disease, or cirrhosis of the liver

ALBUMIN (3.4 TO 5.4 G/DL) The albumin test measures the amount of albumin in

serum, the clear liquid portion of blood and determines if the liver is making enough albumin. This test helps in determining if a patient has liver disease or kidney disease, or if not enough protein is being absorbed by the body. Albumin is one of the two major proteins in the blood, the other is Globulin.  Albumin also helps carry some medicines and other substances through the blood and is important for tissue growth and healing.  Because albumin is made by the liver, decreased serum albumin may result from liver disease.  It can also result from kidney disease which allows albumin to escape into the urine.  Decreased albumin may also be explained by malnutrition or a low protein diet

CO2 (TOTAL) This test measures the amount of carbon dioxide in

the liquid part of your blood. Carbon dioxide (CO2) is a gaseous waste product made from metabolism. The blood carries carbon dioxide to your lungs, where it is exhaled. Changes in your CO2 level suggest you may be losing or retaining fluid, cause an imbalance in your body's electrolytes. Electrolytes are minerals in your blood and other body fluids.

Abnormal levels of carbon dioxide suggest your body is having trouble maintaining its acid-base balance and your electrolyte balance is upset.

Normal Results: 20 to 29 mEq/L

CALCIUM (8.5 TO 10.2 MG/DL) To build and fix bones and teeth help nerves work make muscles contraction help blood clot and help the heart to work. The Calcium test screens for problems with the parathyroid

glands or kidneys, certain types of cancers and bone problems, inflammation of the pancreas (pancreatitis), and kidney stones.

CHLORIDE (96 to 106 mEq/L)Chloride levels can be used to help monitor high blood

pressure, heart failure and kidney disease.  High levels of chloride, known as hyperchloremia, typically indicate dehydration, metabolic acidosis and other conditions.  Decreased levels of chloride, known as hypochloremia, can indicate kidney disorder, Addison's disease, congestive heart failure and other conditions.

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 OsteoblastsOsteocytesEncased osteoblasts which are connected to each

other by long cellular processes forming a network connected by gap junctions.