Multivariate approach to quality control in clinical chemistry.

When monitoring analyzer performance in the clinical setting, laboratories are required to test multiple concentrations of control material on a daily basis. Because of the nature of laboratory testing, there is the potential for correlation between the concentrations of control material being monitored. Although traditional clinical quality-control approaches make an underlying assumption of independence with respect to the control concentrations, this will not always be the case. The presence of correlation in some circumstances suggests the use of a new approach for evaluating clinical laboratory monitoring data: the multivariate control chart. Such a chart (the chi2 chart) is evaluated and compared with traditional quality-control approaches used in the laboratory setting. Results indicate that the multivariate approach provides an attractive alternative to many traditional methods of quality assurance when control concentrations are correlated.