Interferences in immunoassay--still a threat.

Few things in life are perfect, and unfortunately this also applies to medical diagnostic procedures such as clinical laboratory testing. In spite of the careful efforts of the developers and manufacturers of clinical laboratory tests and the vigilance of the laboratory staffs that perform the testing, most if not all tests are, on occasion, subject to interferences that lead to false-positive or false-negative results (1)(2). Immunoassay tests are no exception. Recent literature has documented false-positive or false-negative results in immunoassays or reports investigations of specific interferences (3)(4). Sources of interferences include plasma (5), serum proteins (e.g., rheumatoid factor, binding proteins) (6)(7), heterophile and anti-animal antibodies (2)(8)(9), drugs and drug metabolites (10)(11), hemolysis (12), agar (13), and cross-reacting substances (14). In most cases, a significant interference is recognized and flagged, but sometimes the interference is unsuspected and undetected. There now is adequate evidence that bad …