T-lymphocyte immunophenotyping blind proficiency testing: a model system for CD4+ T-cells.

Abstract

OBJECTIVE: To develop and evaluate methods and results for blind proficiency testing for CD4+ T-cells by T-lymphocyte immunophenotyping. DESIGN: A model system was developed to submit duplicate specimens for T-lymphocyte immunophenotyping as if they were routine patient specimens rather than proficiency specimens. Testing results were compared both interlaboratory and intralaboratory. The model system was designed to gather information on not just the analysis, but other segments of the total testing process. SETTING: Research facilities at the Graduate School of Public Health, San Diego State University, San Diego CA. PARTICIPANTS: 1) A healthy adult volunteer donating one pint of blood. 2) Laboratories offering T-lymphocyte immunophenotyping. MAIN OUTCOME MEASURES: 1) Feasibility of blind proficiency so that PT specimens are received, analyzed, and reported by laboratories without being identified as 'proficiency specimens.' 2) The ease and cost of such a system. 3) The comparability of results and report content among laboratories. RESULTS: A total of twenty-two laboratories received blind proficiency specimens. The model developed to submit specimens and receive results proved feasible. The interlaboratory coefficient of variation for CD4+ count for the four survey years ranged from 10% to 66% and for the CD4+ percent ranged from 4% to 15%. The per specimen cost in this blind proficiency testing was $437.65, approximately seven and a half times the cost for nonblinded proficiency testing or performance evaluations. CONCLUSIONS: Blind proficiency as a tool to compare laboratory test results for T-lymphocyte immunophenotyping is feasible but adds costs. The model system is useful to examine more of the laboratory total testing process than the analysis segment.