Specimen Collection and Handling
Begin with identification, end with documentation
Collecting a specimen is a chain of custody of quality. Positive patient identification uses two independent identifiers-full name and date of birth or medical record number-never the room number. Verify the order, prepare supplies, and choose a site; avoid an arm with a fistula, mastectomy, or IV line.
Memorize the order of draw because it protects both tube integrity and patient results: blood culture bottles, light-blue sodium citrate, serum tubes (gold/red), heparin (green), EDTA (lavender), and fluoride/oxalate (gray). Additive carryover is the reason: EDTA from a lavender tube can contaminate a later calcium test, and tissue thromboplastin from a needle stick can shorten clotting times.
Tourniquet time should not exceed one minute; prolonged tourniquet causes hemoconcentration and falsely elevated potassium, protein, and cell counts. Use the appropriate gauge-21 g for most venipuncture, smaller for fragile veins-and never force blood through a small needle, which hemolyzes cells.
Capillary collections have their own order: EDTA first, then other additive tubes, serum last. For infants, use the lateral heel, not the fingers; for adults, the side of the fingertip.
Urine and timed collections require patient instructions, correct preservative, refrigeration, and complete documentation of start and stop times.
Traps: confusing order of draw, ignoring a short-draw citrate tube, or accepting a hemolyzed sample. A citrate tube must fill to at least 90% of its capacity to maintain the 9:1 ratio; a short draw is recollected, not topped off.