Processing Controls in Blood Collection Tubes Reveals Interference

Central tenets of quality control (QC) and quality assurance are that ( a ) controls should be handled by the regular staff, and ( b ) they should be treated the same way as an equivalent patient specimen. This is not always adhered to in routine practice, and recent problems with blood collection tubes underline this point (1)(2)(3)(4). Collection of blood in certain batches of Vacutainer® SST tubes was associated with errors in some immunoassays on certain immunoassay platforms [e.g., biases of 20% to 30% for total thyroxine (T4), total triiodothyronine (T3), and cortisol and −15% to 20% for follicle-stimulating hormone (FSH)]. These errors have been attributed to contamination of samples with surfactants that are used to coat the tubes; the surfactant can release reagent antibodies from some solid-phase materials used in immunoassay methods (5)(6).Blood specimens for testing are removed through a metal needle into a blood collection tube. The tube and its contents are centrifuged to isolate serum, and the serum is either sampled directly from this tube or transferred to another tube from which …