Clinical Chemistry

CLINICAL CHEMISTRYI. PROTEINS AND TUMOR MARKERS PROTEINS: PLASMA, URINARY, CSF TUMOR MARKERS: PSA, APP, CEA, B-HCG, CA 15-3, CA 125, CA 19-9 II. NONPROTEIN NITROGENOUS COMPOUNDS III. CARBOHYDRATES IV. LIPIDS AND LIPOPROTEINS V. ENZYMES PROTEINS AND TUMOR MARKERS PROTEINS  Macromolecules made up of amino acids, with each AA being linked to another via a peptide bond  Functions: o Energy production: Proteins can be broken down into AA that can be used in the citric acid cycle to produce energy o Water distribution: Maintain the colloidal osmotic pressure between different body compartments o Buffer: The ionisable R groups of the individual AA provide buffering capacity by binding or releasing H+ ions as needed o Transporter: Binding of proteins to hormones, free Hgb, lipids, drugs, Ca, unconjugated bilirubin allows movement of these and other molecules in the circulation o Antibodies: Function as receptors for hormones so that the hormonal message can activate cellular components; some hormones are protein in nature e.g. ACTH, FSH, TSH o Structural proteins:Collagen is the fibrous component that maintains the structure of body parts o Enzymes: catalysts that accelerate chemical reactions PLASMA TOTAL PROTEIN 1. REGULATION  The liver synthesizes most of the plasma proteins. Plasma cells synthesize the Igs.  Proteins are synthesized from AA.  When proteins degrade, their constituent AA undergoes deamination with the formation of ammonia, which is converted to urea to excretion in the urine.  Some cytokines released at the site of injury or inflammation cause the liver to increase synthesis of the acute- phase reactant proteins (nonspecific response to inflammation that may be caused by autoimmune disorders, infections, tissue injury from tumors, MI, trauma, or surgical procedures)  Some proteins will decrease in concentration – negative acute-phase proteins, e.g. prealbumin (transthyretin), albumin, and transferrin.  Immunoglobulins – humoral Ab produced in response to foreign Ag for the purpose of destroying them  Reference ranges: Total protein 6.5 – 8.3 g/dL Changes in total protein concentration:  Hypoproteinemia – caused by urinary loss, GIT inflammation, liver disorders, malnutrition, inherited immunodeficiency disorders, and extensive burns  Hyperproteinemia – caused by dehydration, increased protein production (gammopathies) and chronic inflammatory disease associated with paraprotein production. Clinical Significance of the Major Proteins 1. Prealbumin (transthyretin)  Indicator of nutritional status; transports thyroid hormones  Decreased in liver disorders, inflammation, malignancy, poor nutrition  Increased in steroid therapy, CRF, alcoholism 2. Albumin  Synthesized in the liver  Highest concentration of all plasma proteins  Binds many analytes for transport in blood, including unconjugated bilirubin steroids, ions such as Ca and Mg, FA, and drugs  Significantly contributes to plasma osmotic pressure  Decreased in liver disorders, malabsorption, muscle-wasting diseases, severe burns, renal diseases (nephrotic syndrome, glomerulonephritis), starvation, malnutrition 3. Alpha 1 – Antitrypsin  Acute-phase reactant  A protease inhibitor that neutralizes trypsin-type enzymes that can damage structural proteins  Decreased in emphysema-associated pulmonary disease and severe juvenile hepatic disorders that may result in cirrhosis  Increased in inflammatory disorders 4. Alpha 1 – Fetoprotein (AFP)  Is synthesized during gestation in the yolk sac and liver of the fetus, peaking at 13 wks and declining at 34 wks.  Normally adult levels are very low.  Maternal serum AFP is measured between 15 and 20 wks AOG and is reported as multiples of the median (MoM)  Increased level: neural tube defects, spina bifida, and fetal distress  Decreased level: Down syndrome, trisomy 18  In adults, increased levels of AFP can be indicative of hepatocellular carcinoma and gonadal tumors. 5. Alpha 1 – Acid glycoprotein (orosomucoid)  Acute-phase reactant; bonds to basic drugs  Increased in inflammatory disorders such as RA, pneumonia and conditions associated with cell proliferation  Decreased in nephrotic syndrome 6. Haptoglobin  Alpha 2 – globulin that binds free hemoglobin; an acute-phase reactant  Increased in inflammatory conditions, burns, trauma  Decreased in intravascular hemolysis because of formation of a haptoglobin-hemoglobin complex for removal by the liver 7. Ceruloplasmin  Ab acute phase reactant that is an a2-globulin, copper-containing protein with enzymatic activity  90% of serum copper is bound in ceruloplasmin  Increased in pregnancy, inflammatory disorders, malignancies, and with intake of oral estrogen and OCP  Decreased in Wilson disease, malnutrition, malabsorption, severe liver disease 8. a2-Macroglobulin  proteolytic enzyme inhibitor thatinhibits thrombin, trypsin, and pepsin  increased in nephrotic syndrome, contraceptive use, pregnancy, estrogen therapy  decreased slightly in acute inflammatory disorders and prostatic cancer, decreased markedly in acute pancreatitis 9. Transferrin  β-globulin that transport iron  decreased in infections, liver disease, and nephrotic syndrome  increased in iron-deficiency anemia and pregnancy 10. C-reactive protein (CRP)  β-globulin acute-phase reactant  increased in tissue necrosis, RF, infections, MI, RA gout 11. Immunoglobulins (Ig): Antibodies  Five major classes: IgA, IgD, IgE, IgG, and IgM  Synthesized in plasma cells as an immune response  One of the Igs will be increased in a monoclonal gammopathy (e.g. multiple myeloma) – generally associated with increase in IgG, IgA, or IgM  IgG can cross the placenta.  Increased in liver disorders, infection, and collagen disease  Decreased in presence of increased susceptibility to infection and when a monoclonal gammopathy is associated with an increase in another immunoglobulin  IgA levels increase after birth.  Increased in liver disorders, infections, and autoimmune diseases  Decreased in inhibited protein synthesis and hereditary immune disorders  IgM cannot cross the placenta; it is made by the fetus  Increased in various bacterial, viral and fungal infections and Waldenstrom macroglobulinemia  Decreased in renal disease associated with protein loss and immunodeficiency disorders  IgD is increased in liver disorders, infections, connective tissue disorders  IgE is increased in allergies, asthma, and hay fever, parasitic infections Proteins In Other Body Fluids  Urinary Proteins  Quantifications performed on 24-hour urine specimens  Reference range urine total protein: 1-4 mg/dL; <100 mg/day Clinical significance of proteinuria  May result from tubular or glomerular dysfunction, multiple myeloma, Waldenstrom macroglobulinemia, nephrotic syndrome  Bence Jones protein may be found in urine of patients with multiple myeloma  Glomerular membrane can be damaged in diabetes, amyloidosis, and collagen diseases.  Glomerular dysfunction can be detected in its early stages by measuring microalbumin in urine.  Microalbuminuria – the quantity of albumin in urine is greater than normal, yet it undetectable by urine dipstick method; generally precedes nephropathy  Reference range for urine albumin: < 30 mg/day 2. CSF  Reference range 15-45 mg/dL Clinical Significance  Increased in viral, bacterial, and fungal meningitis, traumatic tap (bloodly), multiple sclerosis, herniated disk, and cerebral infarction  Decreased in hyperthyroidism and with CNS leakage of CSF TUMOR MARKERS Tumor Marker Utilization  In general, tumor markers are not very useful in diagnosis.  Useful in tumor staging, monitoring therapeutic responses, predicting patient outcomes, and detecting cancer recurrence. Ideal Characteristic for Tumor Markers includes:  Measured easily  High analytical sensitivity of assay method  High analytical specificity of assay method  Cost-effective  Test result contributes to patient care and outcome  Prostate Specific Antigen (PSA)  Function: 1. Produced by epithelial cells of the prostate gland and secreted into seminal plasma 2. Glycoprotein protease that functions in liquefaction of seminal coagulum  Forms of PSA found in the blood 1. Enveloped by protease inhibitor, a2-macroglobulin; lacks immunoreactivity 2. Complexed to another protease inhibitor, a1-antichymotrypsin; immunologically detectable 3. Free PSA, not complexed to protease inhibitor, immunologically detectable 4. Total PSA assays measure complexed and free PSA dorms, as they are immunologically detectable  Specificity 1. A tissue-specific marker but not tumor specific 2. Small amount present in serum normally 3. Lacks specificity because serum level of PSA is increased in BPH as well as in adenocarcinoma of the prostate  Prostate cancer detection 1. Early detection guidelines endorse lower cutoff of PSA up to 2.5 ng/mL 2. PSA >2.5 ng/mL perform biopsy 3. PSA velocity is measurement of the rate of change per year. a. Biopsy recommended when PSA rises more than 0.75 ng/mL/year even when PSA is <2.5 ng/mL. 4. Free PSA: Men with prostate cancer tend to have lower % free PSA (free PSA/total PSA) than men with benign disease. Lower % free PSA is associated with a higher risk of prostate cancer. 5. PSA is used to monitor therapeutic response and to follow radical prostatectomy.  α1-Fetoprotein (AFP)  Oncofetal glucoprotein antigen 1. Synthesized in liver, yolk sac, and GI tract of fetus 2. Fetal serum AFP peaks at 12-15 weeks of gestation with levels of 2-3 mg/mL. 3. At birth levels fall to 50 µg/mL, and at 2 years of age only trace amounts are present. 4. Adult levels <20 ng/mL Clinical Significance  Increased level of AFP in adults are associated with hepatocellular carcinoma, testicular, and ovarian teratocarcinomas, pancreatic carcinoma, gastric and colonic carcinomas.  Increased levels in adults are also seen in non-malignant disorders, including viral hepatitis and chronic active hepatitis  Useful in monitoring therapeutic response of cancer patient to treatment protocols  In pregnancy, increased maternal serum levels are associated with spina bifida, neural tube defects, and fetal distress. Decreased levels of maternal serum AFP are associated with increased incidence of Down syndrome.  Carcinoembryonic antigen (CEA)  Oncofetal glycoprotein antigen  Normally found in epithelial cells of the fetal GI tract Clinical Significance in adults 1. Increased levels of CEA are associated with adenocarcinoma of digestive tract and colorectal carcinoma. 2. Elevations are seen in other malignancies and noncancerous disorders. 3. Useful in monitoring therapeutic response of cancer patients to treatment protocols.  Enzyme immunoassay methods are used for measurement. 4. Human chorionic gonadotropin (hCG)  A glycoprotein composed of α- and β- subunits. The β- subunit is unique and not common to other hormones; α- subunit is common to other hormones.  Normally secreted by the trophoblast cells of the placenta  Increased secretion is associated with trophoblastic tumors, choriocarcinoma, nonseminomatous testicular tumors, and ovarian tumors.  Useful for monitoring the progress of patients  Immunoassay measurement is made of β-hCG 5. CA 125  Mucin glycoprotein antigen  Marker for ovarian and endometrial cancer  Useful for monitoring the progress of patients 6. CA 19-9  Glycolipids blood group antigen-related marker  Marker for pancreatic, colorectal, lung, and gastric carcinomas  Useful for monitoring the progress of patients 7. CA 15-3  Mucin glycoprotein antigen  Useful for monitoring therapeutic response and for detecting recurrence of breast cancer in patients previously treated  Elevated levels observed in non-malignant diseases such as chronic hepatitis, tuberculosis, and SLE. NONPROTEIN NITROGENOUS COMPOUNDS  UREA  CREATININE  URIC ACID  AMMONIA 1. UREA Regulation of Urea  Major nitrogen-containing compound in the blood  Results from protein catabolism  Synthesized in the liver from the deamination of AAs  Excreted by the kidneys Clinical Significance  Abnormal urea levels may be due to prerenal, renal or post renal d/o  ↑ Renal failure, GN, UTI, CHF, dehydration, increased protein catabolism  ↓ Severe liver disease, vomiting, diarrhea, malnutrition  Blood urea nitrogen (BUN) – an older term still in use, terminology based on previous methodology where nitrogen was measured. To convert BUN to urea: BUN x 2.14 = Urea 2. CREATININE Regulation:  A waste product of muscle contraction that is formed from phosphocreatinine, a high energy comp.  Levels regulated by kidney excretion.  Measurements of creatinine in serum and urine (creatinine clearance) are used to assess the glomerular filtration rate  Levels not changed by diet or rate of urine flow  Creatinine is not reabsorbed by renal tubules. Clinical Significance  ↑ Renal disease, renal failure 3. URIC ACID Regulation  Major waste product of purine (adenosine and guanisine) catabolism  Synthesized in the liver  Elimination from the blood is regulated by the kidneys through glomerular filtration  Some excreted through the GI tract Clinical Significance  ↑ Gout, renal d/o, tx of myeloproliferative d/o, lead poisoning, lactic acidosis, toxaemia of pregnancy, Lesch-Nyhan syndrome  ↓ severe liver disease as a secondary d/o, tubular reabsorption d/o, drug induced 4. AMMONIA Regulation  Ammonia produced from deamination of AAs  Hepatocytes convert ammonia to urea for excretion  With severe liver cell malfunction, blood levels of ammonia increase  Ammonia is neurotoxic Clinical Significance  ↑ hepatic failure and Reye syndrome CARBOHYDRATES Glucose Metabolism  During fast, the blood glucose level is kept constant by mobilizing the glycogen stores in the liver.  During long fast, gluconeogenesis is required to maintain blood glucose levels because glycogen stores are used up in about 24-48 hours. Hypoglycemia: FBS < 50 mg/dL Hyperglycemia: FBS> 200 mg/dL Hormones Affecting Blood Glucose Levels  Insulin  Beta cells of the islets of Langerhans  Promotes entry of glucose into the liver, muscle, and adipose tissue to be stored as glycogen and fat  Inhibits the release of glucose from the liver  Somatostatin  Delta cells of the islets of Langerhans  Inhibits secretion of insulin, glucagon, and growth hormone  Results in an increase in plasma glucose level  Growth hormone and adenocorticotropic hormone (ACTH)  Secreted by the anterior pituitary  Raise blood glucose  Cortisol  Secreted by the adrenal glands  Stimulates glycogenolysis, lipolysis, and gluconeogenesis  Epinephrine  Secreted by the medulla of the adrenal glands  Stimulates glycogenolysis, lipolysis, and gluconeogenesis  Inhibits secretion of insulin  Physical or emotional stress causes increased secretion of epinephrine and an immediate increase in blood glucose levels.  Glucagon  Secreted by the α cells  Increases blood glucose by stimulating glycogenolysis and gluconeogenesis  Thyroxine  Secreted by the thyroid gland  Stimulates glycogenolysis and gluconeogenesis  Increase glucose absorption from the intestines Renal Threshold for Glucose (RTG)  Glucose is filtrated by the glomeruli, reabsorbed by the tubules, and normally not present in urine.  If the blood glucose level is elevated, glucosuria occurs.  RTG varies between 160 and 180 mg/dL.  When blood glucose reaches this level or exceeds it, the renal tubular transport mechanism becomes saturated, which causes glucose to be excreted into the urine. ABNORMAL CARBOHYDRATE METABOLISM  Diabetes mellitus Type 1 DM  Insulinopenia  Required tx with insulin to sustain life  An autoimmune disorder affecting β cells  Peak incidence in childhood and adolescence, but may occur at any age  Primary sx include polyuria, polydipsia and weight loss  Ketosis-prone: Can produce excess ketones, resulting in diabetic ketoacidosis (DKA) Type 2 DM  Defect in insulin secretion and cellular resistance to insulin  Generally responds to dietary intervention and oral hypoglycemic agents, but some may require insulin therapy.  Associated with obesity and sedentary lifestyle  Sx include polyuria, polydipsia, and weight loss  Associated with age over 40, but becoming a significant problem in children and adolescents  Non-ketosis prone: without exogenous insulin or oral hypoglycemic medication, these individuals will have an elevated glucose but will not go into DKA. Gestational diabetes mellitus (GDM)  Onset of DM during pregnancy  Return to normal metabolism seen after childbirth  There is an increased chance that type 2 DM may develop later in life. 2. Inherited disorders of carbohydrate metabolism Glycogen storage disease  Inherited diseases involving the deficiency of particular enzymes  Deficiencies cause defects in the normal metabolism of glycogen  Von Gierke, type I: G6PD  Pompe, type II: α-1, 4-glucosidase deficiency 3. Galactosemia  A deficiency or absence of galactokinase, galactose 1-phosphate uridyl transferase, or uridyl diphosphate galactose  Galactose is found in milk as a component of lactose, with galactosemia generally identified in infants.  Most commonly, galactose 1-phosphae uridyl transferase is deficient, which leads to excessive galactose in blood and excretion in urine. Laboratory Diagnosis  Fasting plasma glucose Normal < 100 mg/dL Impaired 100-125 mg/dL  Provisional Dx of DM is made when FPG ≥ 126 mg/dL.  The Dx must be confirmed by one of the three methods described in the following outline: Diagnosis of DM:  A plasma glucose analysis that yields any one of the following results is diagnostic for the presence of DM, provided that unequivocal hyperglycemia is apparent.  If unequivocal hyperglycemia is not apparent, the glucose result must be confirmed by repeat analysis on a subsequent day using any one of the ff. 3 methods: a. Physical sx and a casual plasma glucose level of ≥ 200 mg/dL b. FPG level that is ≥ 126 mg/dL (fasting defined as no caloric intake for minimum of 8 hours) c. Plasma glucose level of ≥ 200 mg/dL at 2-hr point of an OGTT. GDM  A woman at high risk of GDM should have an initial screening early in the pregnancy, and if found negative, retesting done 24-28 weeks of AOG  For women of average risk, testing should be performed at 24-28 AOG  For GDM, FPG ≥ 126 mg/dL or a casual plasma glucose ≥ 200 mg/dL is diagnostic  If unequivocal hyperglycemia is not apparent, retesting must be performed on a subsequent day.  Two-step approach: GCT + OGTT  Initial screening: Glucose Challenge Test a. 50-g oral glucose load (time of day or time of last meal not relevant) b. Plasma is tested at 1 hour, and if glucose threshold value ≥ 140 mg/dL, an OGTT is performed c. Some experts recommended using a threshold value of ≥ 130 mg/dL  OGTT – oral ingestion of 100 g of glucose  Must meet or exceed two or more of the ff criteria: 1. FPG > 95 mg/dL 2. 1-hr > 180 mg/dL 3. 2-hr > 155 mg/dL  Alternatively, a 75-g glucose load may be used and glucose measured through the 2-hour period. OGTT  Patient preparation:  Unrestricted CHO-rich diet for 3 days before the test with physical activity, restrict medication on the test day, 12-hr fast required, no smoking  Adult patient ingests 75 g of glucose in 300-400 mL of water and children 1.75 g/kg up to 75 g of glucose. For assessment of GDM, 50 g, 75 g, or 100 g of glucose may be used (see previous)  Plasma glucose specimen is collected fasting at 10 min, before glucose load and 2-hr after. Urine glucose may be measured.  Impaired fasting glucose: FPG is between 110 and 125 mg/dL  Impaired glucose tolerance (IGT): FPG ≤ 126 mg/dL and 2-hr plasma glucose level (OGTT) between 140-199 mg/dL  DM: FPG ≥ 126 mg/dL or the 2-hour glucose is ≥ 200 mg/dL HbA1c  Glycated/glycosylated hemoglobin  HbA composed of 3 forms, HbA 1a , HbA 1b , and HbA 1c , which are referred to as glycated or glycosylated hemoglobin. HbA 1c is the main form.  Glycated Hb is formed from the nonenzymatic, irreversible attachment of glucose to HbA 1a  Measurement of glycated Hb reflects blood glucose levels for the past 2-3 months.  Useful in monitoring effectiveness and tx and compliance of diabetic individual to tx protocol  Specimen collection: Nonfasting blood drawn in EDTA tubes  Reference range: 4-6 % HbA 1c Effective treatment range < 7% HbA 1c LIPIDS AND LIPOPROTEINS LIPID STRUCTURE 1. FAs  Exist as short, medium, and long chains of molecules that are major constituents of triglycerides and phospholipids.  Minimal amounts bound to albumin and circulate free (unesterified) 2. Triglyceride (TG)  Formed from one glycerol molecule with 3 FA molecules attached viva ester bonds  Comprise 95% of all fats stored in adipose tissue  Transported by chylomicrons and VLDL (very low density lipoprotein)  Metabolism involves releasing the FA to the cells for energy, then recycling the glycerol into the TG  Lipase, lipoprotein lipase, epinephrine, and cortisol break sown TGs. 3. Cholesterol  Unsaturated steroid alcohol; exists in the esterified form. Where a FA forms an ester bond at carbon-3, & free (unesterified) form  Precursor for synthesis of bile acids, steroid hormones, & vit. D  LDL is the primary carrier of cholesterol 4. Phospholipid  Composed of one glycerol molecule and 2 FA molecules attached via ester bonds  Found on the surface of lipid layers  Major constituents of cell membranes and outer shells of lipoprotein molecules Classification of Lipoproteins (Lp) 1. Lipoproteins  are molecules that combine water insoluble dietary lipids and water-soluble proteins (apolipoproteins) so that lipids can be transported throughout the body. Micelles are spherical and have an inner core of neutral fat. 2. Chylomicrons are the largest Lps and have the lowest density  Formed in the intestines and transport TGs after a meal, giving serum a turbid appearance.  Low density: chylomicrons will float to the top and form a creamy layer when plasma is stored overnight  Composed of 86% TG, 5% cholesterol, 7% phospholipid, and 2% apolipoprotein  Enter the circulation and are metabolized to remnant particles for uptake and further modification by the liver. 3. Very-low-density lipoprotein (VLDL)  Carries endogenous TGs synthesized in the liver  Composed of 55% TG, 19% cholesterol, 18% phospholipid, 8% apolipoprotein  Secreted into the blood by the liver for metabolism in peripheral tissues 4. Intermediate-density lipoprotein (IDL)  A transitional form, as it is formed from VLDL and then further modified in the liver to LDL  IDLs carry endogenous TGS cholesterol esters  Composed of 23% TG, 38% cholesterol, 19% phospholipid, 19% apolipoprotein 5. Low-density lipoprotein (LDL)  Major cholesterol carrier  Transports a large amount of endogenous cholesterol  LDL is easily taken up by cells, so elevated levels are associated with increased risk for atherosclerosis  Composed of 50% cholesterol, 22% phospholipid, 6% TG and 22% protein  Brings cholesterol to peripheral cells for membrane synthesis and formation of adrenal and reproductive hormones. 6. High-density lipoprotein (HDL)  Synthesized in the intestine and liver cells  Recycled chylomicron and VLDL molecules  50% protein, 28% phospholipids, 19% cholesterol and 3% TG  Has apoproteins A-I, mainly, and A-II on its surface  Removes excess cholesterol from peripheral tissues and transports it to other catabolic sites (antiatherogenic effect) 7. Lp(a)  Composed primarily of cholesterol esters, phospholipids and apolipoprotein (a) and B-100  Elevated levels assoc. with increased risk for coronary heart disease, MI, and cerebrovascular disease Clinical Significance  Abnormal lipid metabolism can be due to genetic defects or it can be acquired.  Abnormal lipid metabolism is associated with risk of CAD and other disorders.  The National Cholesterol Education Program established the Adult Treatment Panel III Classification (ATP III), which sets cutoff values for cholesterol and triglyceride levels based on a 9- to 12- hour fast. TOTAL CHOLESTEROL REFERENCE RANGE Desirable Borderline High High Total Cholesterol (mg/dL) < 200 200-239 ≥240 HDL CHOLESTEROL REFERENCE RANGE Protective against Heart Disease The Higher, the Better Major Risk Factor for Heart Disease HDL Cholesterol (mg/dL) ≥60 40-59 <40 LDL CHOLESTEROL REFERENCE RANGE Optimal Near optimal Borderline High Very High <100 100-129 130-159 160-189 ≥190 TRIGLYCERIDE REFERENCE RANGE Normal Borderline High Very High Triglyceride (mg/dL) <150 150-199 200-499 ≥500 Clinical Significance Cholesterol  ↑ linked to atherosclerosis, CAD and increased for MI  ↓ various forms of liver disease, most notably alcoholic cirrhosis HDL Cholesterol  ↑ HDL decreases the atherosclerotic process – decreased risk of CAD  ↓ increased risk of coronary artery disease LDL Cholesterol  LDL is directly associated with atherosclerosis and CAD Triglyceride Test  ↑ in Type I, IIb, IV, and V hyperlipoproteinemias, pancreatitis alcoholism, obesity, hypothyroidism, nephrotic syndrome, and storage diseases (Gaucher, Niemann-Pick) ENZYMES AND CARDIAC ASSESSMENT ENZYMES  Proteins that function as biological catalyst  Neither consumed nor permanently altered during a chemical reaction  Appear in the serum in increased amounts after cellular injury or tissue damage  Based on the px sxs, several enzymes may be chosen for analysis to determine if a pattern develops that aids in identifying the tissue source source of the enzyme elevation 1. Lactate dehydrogenase (LD) Tissue location 1. Highest concentrations: liver, heart, skeletal muscle, kidney, erythrocytes 2. LD isoenzymes a. Each LD isoenzymes is a tetramer with five isoenzymes types: LD-1 & LD-2 – asso. with AMI and RBC destruction LD-3- asso. with pulmonary disorders, pancreatitis and lymphocytosis LD-4 & LD-5 – asso. With liver & skeletal muscle d/o Clinical significance: 1. ↑ cardiac disorders (AMI)  Hepatic diseases (viral hepatitis, cirrhosis, infectious mononucleosis), skeletal muscle dses  Haemolytic and hematologic d/o, pernicious anemia, neoplastic d/o (ALL) 2. In AMI, LD levels rises within 8-12 hours, peak at 24-48 hours, and returns to normal in 7-10 d. 2. Creatinine kinase (CK) and CK isoenzymes Tissue location 1. Highest concentrations: Skeletal muscle, heart muscle, brain tissue 2. CK isoenzymes a.Two subunits: M for muscle and B for brain b. CK-MM (CK-3), CK-MB (CK-2), and CK-BB (CK-1) c. CK-MB ↑ indicative of AMI when used in conjunction with other markers, such as troponin DDx: skeletal muscle damage CK-MM ↑ assoc. with skeletal muscle and heart muscle d/o CK-BB ↑ in CNS d/o & tumor of various organs, e.g. prostate Clinical Significance 1. ↑ total CK asso. with cardiac d/o, such as AMI, skeletal m. d/o, e.g. muscular dystrophy Occasionally, d/o of the CNS, incl. seizures and CVA 2. CK-MB >6% of total CK: suggestive of AMI When AMI suspected, troponin is assayed in conjunction with CK-MB, and sometimes myoglobin too. Following AMI, CK-MB levels rise within 4-6 hrs, peak at 12-24 hrs, and return to normal within 2-3d. 3. Aspartate aminotransferase (AST)  Highest in heart, liver, and skeletal m. Clinical Significance 1. AST is used to evaluate hepatocellular disorders (up to 100x upper reference limit in viral hepatitis, hepatitis, up to 20x in infectious mononucleosis, and up to 4x in cirrhosis) Skeletal m. d/o (up to 8x) Pulmonary emboli (up to 3x) Acute pancreatitis 2. In AMI, AST rises within 6-8 hours, peaks at 18-24 hrs, & returns to normal within 4-5 d. 4. Alanine aminotransferase (ALT)  Highest in liver, with lesser amounts in other tissues, including kidneys and erythrocytes Clinical Significance:  Hepatocellular d/o (hepatitis, cirrhosis) exhibit higher ALT. ALT is more specific for liver disease than AST.  Elevated ALT & AST = to assess liver involvement in an AMI 5. Alkaline phosphatase (ALP)  Highest in liver, bone, intestine, spleen, kidney, placenta Clinical Significance:  ↑ in hepatobiliary and bone d/o (with osteoblastic involvement)  In obstructive hepatobiliary d/o – ALP levels are increased more significantly than ALT and AST a. In biliary tract obstruction, synthesis of ALP is induced by cholestasis, which cause ALP levels to rise 3-10x b. In hepatitis and cirrhosis, (hepatocellular conditions) – ALP rise up to 3x c. Highest elevations of ALP seen in Paget disease 6. Acid phosphatase (ACP)  Highest in prostate gland, with lesser amount in bone (osteoclasts), liver spleen, erythrocytes, platelets Clinical Significance 1. Increased in prostate cancer, BPH, bone disease, Paget disease, breast cancer with bone metastases, Gaucher disease, platelet damage, idiopathic thrombocytopenic purpura 2. Use of ACP in forensic cases involving rape – vaginal washings containing seminal fluid would exhibit ACP activity 7. Gamma-glutamyltransferase (GGT)  Found in liver (canaliculi of hepatic cells and epithelial cells lining biliary ductules), kidneys, pancreas, intestine, etc. Clinical Significance 1. Increased levels in all hepatobiliary disease:  2-5x – viral hepatitis, alcoholic cirrhosis  Very sensitive indicator for these conditions 2. Higher levels (5030x) observed in intra- and posthepatic biliary tract obstruction, increases before and remains elevated longer than ALP, AST, ALT 3. GGT activity induced by drugs (e.g., phenobarbital and phenytoin) and by alcohol consumption 8. Amylase  Found in pancreas, salivary glands, SI, FT, and other tissues Clinical Significance 1. Acute pancreatitis: increased levels in 2-12 hrs after the onset of pain, peak hrs, return to normal in 3-4 d. 2. Increased: Mumps, perforated peptic ulcer, intestinal obstruction, cholecystitis, ruptured ectopic pregnancy, mesenteric infarction, acute appendicitis 9. Lipase (LPS) Tissue location  Found in pancreas, with lesser amounts in gastric mucosa, intestinal mucosa, adipose tissue Clinical significance 1. Acute pancreatitis – increased levels in 4-8 hours after the onset of pain, peak in 24 hrs, return to normal in 8-14 d. 2. Increased: Perforated peptic ulcer, duodenal ulcers, intestinal obstruction, cholecystitis 10. Glucose-6-phosphate dehydrogenase (G6PD)  Found in RBCs, adrenal glands, thymus, lymph nodes, spleen Clinical significance 1. Decreased: Primary importance of G6PD is in cases of deficiency, inherited as a sex-linked trait (x- chromosome) In G6PD deficiency a hemolysis occurs with administration of antimalarial drugs or primaquine, infections and after ingestion of fava beans. 2. Increased: Megaloblastic anemias and AMI CARDIAC PROFILE  Upon arrival to the ER, a cardiac profile would be ordered to establish baseline values. Then the cardiac profile would be ordered for several sampling in 3- to 8—hr intervals over a 12-24 hr pd. Frequently blood is drawn every 3 hrs for analysis during the 1 st 12 hrs.  Laboratory tests to assess AMI include cardiac troponin T or I, CK-MB, and sometimes myoglobin. In many institutions, sampling and testing is halted since it is considered diagnostic for AMI. 1. TROPONIN  Troponins T, I, and C form a complex of 3 proteins that bind to filaments of skeletal muscle and cardiac muscle to regulate muscle contraction. Clinical Significance 1. cTnT or cTnI (cardiac troponin T or cardiac troponin I) is used as an AMI indicator because of specificity and early rise of serum concentration following AMI. 2. In cases of AMI cTnT increases in 3-4 hrs, peaks in 10-24 hrs and returns to normal in 10-14 d. whereas, cTnI increases in 3-6 hrs, peaks in 14-20 hrs, and returns to normal in 5-10 d. 2. MYOGLOBIN  Found in skeletal and cardiac muscles Clinical significance 1. Increased in skeletal muscle injuries, muscular injuries, muscular dystrophy and AMI 2. Released early in cases of AMI, rising in 1-3 hrs, peaks in 5-12 hrs, and returns to normal in 18-30 hrs. However, it is not tissue specific. It is better used as a negative predictor in the first 2-4 hrs following chest pain. NATRIURETIC PEPTIDES: POLYPEPTIDE HORMONES a. Three forms: ANP, CNP, BNP b. Effects are minimal;  Function – promote excretion of Na and H2O by increasing the GFR and decreasing the renal tubular reabsorption of Na. c. B-type (brain) natriuretic peptide (BNP) is synthesized in and secreted from myocardial ventricles in response to ventricular volume expansion and pressure overload. BNP causes vasodilation and promotes Na and H2O loss, thus reducing fluid load in the heart to improve cardiac function. d. Clinical significance: BNP increased in CHF High Sensitivity CRP (hs-CRP) 1. C-reactive protein (CRP): β-globulin that is an acute-phase reactant 2. Refers to the sensitivity of the assay to determine low level in serum. 3. Clinical significance: Used as a predictor for cardiovascular risk; increased levels seen in inflammation, infection, stress, trauma, and AMI