BD Vacutainer Heparin Tube 4ml (Green — Lithium Heparin, Plasma Chemistry)

Lithium heparin is the standard anticoagulant in green-top chemistry tubes because lithium does not interfere with routine clinical chemistry analytes. Sodium heparin introduces exogenous sodium into the plasma sample, which causes falsely elevated sodium measurements in plasma electrolyte panels. Since sodium is one of the most frequently ordered clinical chemistry tests, sodium heparin would invalidate serum sodium results on every tube drawn. Lithium heparin avoids this problem because plasma lithium is not a routine analyte in standard biochemistry panels. The critical exception: lithium heparin tubes must not be used for therapeutic lithium drug level monitoring, since the tube's lithium heparin would contaminate the sample and produce a falsely elevated plasma lithium result.

Certain tests should not be performed on lithium heparin plasma specimens. Therapeutic lithium drug level monitoring — the heparin itself introduces lithium into the sample, invalidating the result. Coagulation tests (PT, APTT, fibrinogen, D-dimer, coagulation factor assays) — these require the sodium citrate tube as heparin artificially alters all coagulation endpoint times. Some specific immunoassays and molecular biology applications where heparin is a known inhibitor of PCR amplification — heparin plasma is incompatible with PCR-based tests and must not be used for DNA extraction. Blood bank crossmatch and antibody screening — these require EDTA or acid-citrate-dextrose (ACD) tubes. Each laboratory should check the specific test manufacturer's package insert for acceptable specimen types.

The BD Vacutainer PST (Plasma Separation Tube) combines spray-coated lithium heparin (to prevent clotting and produce plasma) with a thixotropic polymer gel separator (to separate plasma from cells after centrifugation). In the plain lithium heparin tube (green, no gel), after centrifugation the plasma supernatant sits directly over the packed cell pellet and must be carefully pipetted or poured off to avoid cellular contamination. In the PST tube (light green Hemogard, gel present), centrifugation causes the gel to migrate to the plasma-cell interface, forming a stable barrier. Plasma can then be aspirated directly from above the gel, or the tube stored and transported without re-mixing of cells. PST eliminates the aliquoting step and is preferred in high-throughput laboratories. The plain heparin tube without gel is preferred for trace element testing and certain assays where gel may interfere.

BD specifies that heparin blood collection tubes should be inverted 8 to 10 times gently immediately after blood collection. This is consistent with CLSI guidelines for heparin tubes. The inversions distribute the dry spray-coated lithium heparin uniformly throughout the blood sample to ensure complete anticoagulation. Inadequate mixing leaves areas of the sample without sufficient heparin concentration, allowing partial clotting — fibrin threads and microclots that can block analyser sample probes, produce inaccurate results, and cause instrument alarms. Vigorous shaking must be avoided as it causes haemolysis, which interferes with many chemistry assays (notably LDH, potassium, AST, and haemoglobin-dependent measurements).

BD Vacutainer lithium heparin tubes are available in multiple volumes: 3ml (13x75mm, REF 367856) for paediatric or low-volume adult testing; 4ml (13x75mm, REF 367861) for standard adult chemistry panels; 6ml (13x100mm, REF 367884) for larger volume testing requirements; and 10ml (16x100mm, REF 367886) for high-volume multi-analyte panels or research applications. The PST gel separator variants are available in 3ml (REF 367960) and 4.5ml (REF 367962) in light green Hemogard closure format. All formats are packaged 100 tubes per box and 1,000 per case. The appropriate volume selection depends on the number of chemistry tests ordered per patient draw, the analyser's minimum and maximum sample volume requirements, and paediatric vs adult patient population.