Challenge Your Exam Readiness With Our Free Phlebotomy Practice Questions

ESR measures the rate at which erythrocytes settle in anticoagulated whole blood. The standard specimen is EDTA (lavender-top) whole blood, mixed thoroughly and analyzed at room temperature within the manufacturer’s specified timeframe (e.g., 4 hours for Westergren methods unless otherwise validated). Option B reflects this requirement. Serum (Option A) is incorrect because ESR requires intact cellular elements in anticoagulated blood. Heparinized plasma (Option C) is not the standard and refrigeration alters viscosity and cell morphology, affecting results. Citrate (Option D) is used in some ESR systems with specific dilutions, but freezing is inappropriate and would lyse cells. Proper mixing (gentle inversions), avoidance of hemolysis, and prompt analysis are essential. Documenting collection time and maintaining tubes upright during measurement are also critical. Understanding matrix and handling ensures valid ESR results, a common hematology preanalytical question on certification exams.