IMPACT OF QUALITY-CONTROL ON ACCURACY IN ENZYME-IMMUNOASSAY TESTING FOR HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 ANTIBODIES

Objective.-To assess use of quality control (QC) material, supplementa l to internal kit controls (calibrators), as protection against errors in enzyme immunoassay testing for human immunodeficiency virus type 1 antibodies. Design.-From August 1994 to January 1996, enzyme immunoas say testing accuracy was assessed for laboratories participating in th e Centers for Disease Control and Prevention Model Performance Evaluat ion Program that provided information regarding their use of QC materi al. Error rates were examined for human immunodeficiency virus type 1 antibody-negative, strongly positive, and weakly positive samples. Res ults.-The overall error rate with QC (2.20%) was significantly (P =.00 23) tower than the error rate without QC (2.90%). With QC use there wa s a significant reduction in the relative risk of error for negative ( P =.014) and weakly positive (P =.0067) samples. After multivariate an alysis, use of QC lowered overall error rate by 29% (P =.0009). Labora tories not using QC were at increased risk of systematic error. Follow ing the Clinical Laboratory Improvement Amendments of 1988 guidelines for QC material was relatively more protective against error than lowe r frequencies/number of levels. Conclusions.-Using QC protected agains t errors in enzyme immunoassay testing for human immunodeficiency viru s type 1 antibodies. Two levels of QC should be used with each run as mandated by the Clinical Laboratory Improvement Amendments of 1988.