A comparison of chemiluminescence immunoassay and radioimmunoassay for the detection of nortestosterone residues in meat samples

A chemiluminescence immunoassay, with a nantiserum raised against 19-nortestorone-3- carboxymethyloxime/bovine serum albumin and the N-(4-aminobutyl)-N-ethylisoluminol conjugate of 19-nortestosterone as tracer is compared to a radioimmunoassay, with an antiserum against 19-nortestosterone-17-hemisuccinate/bovine serum albumin and 19-(6,7-³H) nor testosterone as the radioactive label. Both methods have a similar sensitivity but the limit of quantification is much lower for radioimmunoassay (0.08 μg kg^-1) than for chemiluminescence immunoassay (0.6 μg kg^-1). A more practical appraoch, the limit of decision, is defined which is determined by the analytical results obtained from certified blank reference samples. This concept gives a good qualitative agreement between the two immunoassay techniques and the number of false positive and negative results, as ascertaind by GC/MS, is minimized; this is shown for assays of 38 meat samples.