Reliability of the cloned-enzyme donor immunoassay (CEDIA) for cocaine in human serum in the range between the detection limit and the cut-off

Immunoassays are used worldwide for the rapid screening of drugs. Despite the fact that they are highly valuable tools for the testing of legal and illicit drugs, there is a non-negligable risk of false-positive and false-negative findings and many pitfalls must be taken into account when using these tests in an uncritical manner and without valid confirmation procedures. In order to check the correlation between cloned-enzyme donor immunoassay (CEDIA) readings and exact determined gas chromatography/mass spectrometry (GC/MS) values for benzoylecgonine, a total of 472 serum samples was measured with an immunoassay (CEDIA) as well as GC/MS. As a result, it was shown that in the lower area of concentration, up to approx. 300 ng equ. benzoylecgonine/ml, there is a semiquantitative useful correlation. With higher concentrations, the values shift more and more apart and many runaways are visible. Generally the use of tests for materials other than those declared is excluded from the manufacturer's warranty and is at the user's own risk, but the authors found that many immunochemical tests with a certification only for the use in urine are well suited to the screening of serum samples, and even low readings could be confirmed by GC/MS. With blood or serum as sample, it could be regularly observed that generally very small readings could not only be confirmed with mass spectrometry but could in most cases also be quantified. This was the key factor in determining the rate of confirmation in 495 cases. In total, an incredibly high reliability for the CEDIA cocaine test (via benzoylecgonine) was shown up to the area of detection (detection limit), far below the cut-off. These results confirm the extraordinary sensitivity and specificity of this test also for blood or serum as sample material to be tested.