Evaluation of the rigor and appropriateness of CLIA '88 toxicology proficiency testing standards

The proposed rule for the Clinical Laboratory Improvement Amendments of 1988 (CLIA '88) describes uniform standards for the design of proficiency testing (PT) challenges and for the evaluation of laboratory performance. Successful performance on PT is a condition for laboratory certification by the federal Department of Health and Human Services. We conducted a retrospective evaluation of PT data collected from laboratories participating in the New York State therapeutic substance monitoring/quantitative toxicology PT program to determine how well laboratories performed by proposed PT standards. We found that the unsuccessful performance rate is very low (less than 0.4%) and that laboratories providing limited services are more susceptible to program sanctions than are full-service laboratories. The performance criteria are empirically fixed limits that are not consistent with either the state of practice or the analytical goals based on clinical requirements for good patient care. We suggest that the performance standards, if adopted, would be a weak challenge to the capability of today's therapeutic drug monitoring service and will not provide the impetus to bring analytical performance characteristics into full compliance with analytical goals.