The quality of diagnostic testing may be impaired during shipment of lithium-heparin gel tubes

Background: Provided that basic criteria are fulfilled, it is widely assumed that centrifuged gel tubes may be safely shipped from one center to another. The aim of this study was to evaluate sample stability after shipment of centrifuged serum and lithium-heparin gel tubes from a peripheral collection center to the core laboratory. Methods: The study population consisted in 30 unselected outpatients requiring collection of both serum and lithium-heparin gel tubes. The primary blood tubes were centrifuged, an aliquot was taken and tubes were recapped. All samples were then shipped by courier from the peripheral facility to the core laboratory, located 34 km away (52 min transportation). In the core laboratory the following parameters were assessed: albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), bilirubin, calcium, chloride, cholesterol, creatine kinase (CK), creatinine, C reactive protein (CRP), ferritin, glucose, lactate dehydrogenase (LDH), potassium, sodium, total protein, thyroid stimulating hormone (TSH) and urea nitrogen. Results: Compared with paired aliquots, significant differences were observed for ALT, AST, bilirubin, calcium, chloride, CK, glucose, LDH, potassium and urea nitrogen in lithium-heparin gel tubes, and for calcium, chloride, CK, LDH, potassium and urea nitrogen in serum gel tubes. When percentage variations were compared with the desirable specifications, significant bias was found for AST (+7.8%), calcium (+1.2%), glucose (-3.3%) and LDH (+35%) in lithium-heparin gel tubes. The bias in serum gel tubes was always lower than the desirable specifications. Conclusions: Serum gel tubes seem to have practical advantages over lithium-heparin gel tubes during medium-term transportation, and hence should be preferred for sample shipment.