Assay methods for fentanyl in serum: gas-liquid chromatography versus radioimmunoassay

In this study, two independent laboratories assessed the validity of the fentanyl radioimmunoassay (RIA) by measuring a series of spiked control serum samples and 429 serum samples from 20 patients receiving fentanyl for their anesthesia. Additionally, a gas-liquid chromatographic (GLC) method specific for the parent drug was also applied to the same serum samples. The RIA measurement of fentanyl by the two laboratories resulted in comparable values for both control samples and samples from patients in a range of 0.5-50 ng/ml. The GLC method agreed with both RIA measurements in the spiked control and patient samples. The authors' results demonstrate the validity of the RIA as a measurement technique for fentanyl in human serum samples.