Is it possible to use expired tubes for routine biochemical analysis in dogs?

BACKGROUND Expired collection tubes may be used inadvertently and resampling is not always possible. To date, studies have not been conducted in veterinary medicine to determine whether or not biochemical measurements obtained from specimens collected into expired tubes are accurate enough for clinical decision-making. OBJECTIVES The aims of this preliminary study were to assess the impact of measuring routine plasma biochemical analytes in canine specimens collected in expired tubes and to investigate the relationship between post-expiration time and the magnitude of errors. METHODS Blood specimens were collected from 61 dogs and aliquoted equally into tubes containing lithium heparin and gel. One tube was within the expiration date, and the other tube was up to 11 months post-expiration. Plasma was separated within 1 hour of specimen collection, and concentrations of urea, creatinine, total protein, albumin, total bilirubin, cholesterol, triglycerides, magnesium, calcium, phosphates, sodium, potassium, chloride, total CO(2), and fructosamine and activities of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase (ALP), γ-glutamyltransferase, lactate dehydrogenase, creatine kinase, amylase, and lipase were analyzed immediately and results compared. RESULTS For most analytes there was no significant difference between results from specimens collected in non-expired and expired tubes. For ALP and lipase activities and fructosamine and total CO(2) concentrations, significant differences were found, and results obtained for fructosamine and total CO(2) from specimens in expired tubes may have led to erroneous interpretations. The effect of time since expiration was constant over time. CONCLUSIONS When specimens are processed within 1 hour of collection, results of routine biochemical measurements of blood collected in lithium heparin tubes remain clinically valid for up to 11 months after expiration of tubes for the majority of analytes, except for ALP, lipase, fructosamine, and total CO(2).