Laboratory Operations and Specimen Handling
Order of draw and collection
CLSI GP41 sets the order to limit additive carryover: blood culture bottles first, then sodium citrate (light blue), serum with or without clot activator or gel (red/gold), heparin (green), EDTA (lavender), and sodium fluoride/potassium oxalate (gray). Invert tubes gently the recommended number of times; never shake, because hemolysis releases potassium, LDH, and hemoglobin. Verify two patient identifiers at collection and label at the bedside.
Transport, accessioning, and rejection
Follow test-specific requirements: protect bilirubin from light, transport blood gases and ammonia on ice, and deliver timed specimens within the stated window. Reject specimens that are unlabeled or mislabeled, collected in the wrong tube, underfilled when a precise blood-to-additive ratio matters, grossly hemolyzed for sensitive assays, or delayed beyond stability. Document the rejection and request a redraw.
Worked example
A patient needs PT/INR, a basic metabolic panel (BMP), and a CBC. After any cultures, draw the light-blue citrate tube for PT/INR, then the gold/red serum tube for the BMP, then the lavender EDTA tube for the CBC. If the citrate tube is only half full, reject it: the target ratio is 9 parts blood to 1 part 3.2% citrate, and excess citrate lowers ionized calcium, falsely prolonging PT and aPTT. If EDTA is drawn before citrate, potassium EDTA carryover can chelate calcium in the citrate tube and also prolong clotting times.
Traps
Order of draw is not alphabetical, and additive carryover is a real preanalytical error. Do not assume every test requires fasting, and do not refrigerate whole blood for a CBC or a blood gas. Underfilled citrate tubes and unlabeled tubes are rejections, not results to note and release.