Specialized Laboratory Tests Lecture Notes

Cardiac Enzymes

• Troponin Levels: Preferred test for diagnosing myocardial infarction (heart attack).

  • Specific to heart muscle.
  • Released 1-3 hours post-injury, peaks at 12-24 hours, normalizes in 5-7 days.
  • Sensitive indicators, used when EKG is negative for MI.
  • Serial testing at admission, 4, 8, and 12 hours after chest pain.
  • No special preparation needed.

• Other Enzymes (e.g., CK): Can be falsely elevated in chronic muscular disorders or kidney disease.

Drug Levels Monitoring

• Digoxin Levels: Used for cardiac dysrhythmias.
  • Risk of toxicity; monitored to ensure therapeutic range.
  • Draw blood 30-60 mins before next dose.
  • Apical pulse must be checked before administration; hold if <60 bpm.

Coagulation Studies

• PTT (Partial Thromboplastin Time): Monitors blood clotting ability.

  • Normal range: 21.0-35.0 seconds.
  • Used for patients on heparin.

• PT (Prothrombin Time): Measures clotting function.

  • Normal range: 11.0-13.0 seconds.
  • Monitored for patients on Coumadin (warfarin).

• INR (International Normalized Ratio): Standardizes PT readings across labs.

• Preparation for Coagulation Tests: No fasting required, list of current meds needed.

  • Post-venipuncture: Hold manual pressure longer due to bleeding risk from anticoagulants.

• Dietary Considerations for Coumadin: Limit Vitamin K-rich foods (green leafy vegetables).

  • Adjust doses based on test results to avoid excessive bleeding or clotting.

D-Dimer Test

• Indicates thrombosis (e.g., DVT, PE).
• Elevation suggests clot formation but can be positive in other conditions (e.g., surgery, pregnancy).
• Negative result rules out thrombosis.

BNP (B-type Natriuretic Peptide)

• Produced by heart ventricles; indicates ventricular overload/heart failure.
  • Normal range: <100.
  • Fasting preferred for accurate results.

Autoimmunity & Systemic Rheumatic Disease Tests

• Antinuclear Antibody (ANA) Test: Screens for autoimmune disorders (e.g., lupus, RA).

  • Positive does not confirm disease, used with symptom analysis.

• Rheumatoid Factor & C-Reactive Protein (CRP):

  • RF: Higher in rheumatoid arthritis, other conditions.
  • CRP: Indicates inflammation, used to monitor disease and treatment response.

• Erythrocyte Sedimentation Rate (ESR): Indicates inflammation/necrotic processes.

  • Faster sedimentation rate correlates with inflammation.

Iron Studies

• Ferritin Levels: Indicator of iron stores; reflects iron deficiency before anemia.

• Vitamin B12: Necessary for RBC production, can be deficient in vegetarians or malabsorption syndromes.

• Folate (Folic Acid): Essential for RBC formation, energy production, and WBC function.

  • Deficiency noted in alcoholism, malnutrition, etc.

• Vitamin D: Required for calcium/phosphorus absorption; deficiency leads to bone issues.

  • Fasting required for testing accuracy.