Use of the BD vacutainer rapid serum tube reduces false-positive results for selected beckman coulter Unicel DxI immunoassays.

We investigated the use of serum samples from BD Vacutainer rapid serum tubes (RSTs; BD, Franklin Lakes, NJ) to reduce undetermined interferences contributing to false-positive immunoassay results in heparin plasma samples. Patients being evaluated for suspected myocardial infarction had specimens drawn into an RST in addition to the standard lithium-heparin plasma separator tube (PST). We measured 28 separate analytes in both specimens using immunoassay, electrochemical, and spectrophotometric methods. Higher results were observed in some PST specimens tested for troponin I, creatine kinase-MB isoenzyme, human chorionic gonadotropin, and thyroid-stimulating hormone. These discrepancies were investigated by repeating analyses after recentrifugation of both specimens. Reanalysis gave results for the PST specimens that were lower and agreed well with initial results from RSTs, suggesting false-positive rates of 10.8% for troponin I and about 2% for each of the other 3 analytes. Overall, specimens collected in RSTs had fewer false-positive immunoassay results than specimens collected in plasma separator tubes.