Development of a Web-based Program to Calculate Sample Size for Evaluating the Performance of In Vitro Diagnostic Kits

Background : Many studies evaluating the performance of in vitro diagnostic kits have been criti-cized for the lack of reliability. To attain reliability those evaluation studies should be preceded bysample size calculation ensuring statistical power. This study was intended to develop a web-basedsystem to estimate the sample size, which was often neglected because it would require expert knowl-edge in statistics.Methods :For sample size calculation, we extracted essential parameters from the performancestudies on the 3rd generation anti-hepatitis C virus (HCV) kits reported in the literature. We developeda system with PHP web-script language and MySQL. The statistical models used in this system wereas follows; one sample without power consideration (model 1), one sample with power consideration(model 2), and two samples with power consideration (model 3).Results :Among the articles published between 1989 and 2005, 13 articles that evaluated theperformance of anti-HCV kits were identified by searching with Medical Subject Headings (MeSH).The diagnostic sensitivity was 83-100% with a median of 145 samples (range; 12-1,091) and thespecificity was 97-100% with a median of 1,025 samples (range; 33-4,381). The estimated samplesize would be 280 in the model 1, 817 in the model 2, and 1,510 in the model 3, when we set 2%prevalence of HCV infection, 95% sensitivity of a conventional kit, 97% sensitivity of a new kit , 95%significance level (two-sided test), 2% allowable error, and 80% power.Conclusions :Our study indicates that an insufficient sample size is still a problem in performanceevaluation. Our system should be helpful in increasing the reliability of performance evaluation byproviding an appropriate sample size. (Korean J Lab Med 2006;26:299-306)Key Words