A research note: an analysis of RIA and GC/MS split hair samples from the New Orleans Pretrial Diversion Program

This paper compares the outcomes of hair analysis for cocaine conducted by two different, independently developed analytical methods, one using radioimmunoassay and the other GC/MS chemical ionization. In this study two hair samples were collected from each subject and a sample was sent simultaneously to each laboratory. The assays were done independently with each laboratory being unaware of the results of the other laboratory. The laboratories each developed their own cutoff criteria, and did not utilize the same cutoff criteria. Analysis of the comparative performance shows a strong correlation between the two procedures, although the GC/MS method, which used a lower cutoff value, identified more positive specimens than did the RIA method. Additionally, there were no cases in which the RIA procedure identified a positive sample which was negative according to GC/MS, although a number of GC/MS positive assays were reported as negative by the RIA laboratory.