Assessment of the Corvac blood collection tube for drug specimen processing

The Corvac integrated serum separator tube (TM Monoject Scientific) has been examined for use in processing specimens for drug analysis. This study was undertaken because the SST serum separator tube (Becton-Dickinson) was shown to cause decreases in drug levels of lidocaine, pentobarbital, and phenytoin, which were dependent upon blood volume and time of contact with the gel. Pools of donor blood were spiked with lidocaine or phenytoin and processed in Corvac tubes and red top tubes. Lidocaine levels were depressed by 5.2% when Corvac was used. Phenytoin levels were unchanged. The lidocaine depression was independent of blood volume, time of gel contact, or tube lot number. Paired patient specimens for quinidine, lidocaine, or theophylline analysis were obtained in Corvac and red top tubes. Lidocaine levels were depressed by 6.0% (p less than 0.01). Quinidine and theophylline levels were unchanged. All drug analyses were carried out using the Syva enzyme multiplied immunoassay technique. The Corvac tube has been shown to cause decreased levels of lidocaine but not of the other drugs tested. Corvac (silicone gel) results differ from SST (polyester gel) results because of the different construction of these tubes.