POOLING URINE SAMPLES FOR LIGASE CHAIN-REACTION SCREENING FOR GENITALCHLAMYDIA-TRACHOMATIS INFECTION IN ASYMPTOMATIC WOMEN

The accuracy of pooling urine samples for the detection of genital Chl amydia trachomatis infection by ligase chain reaction (LCR) was examin ed, A model was also developed to determine the number of samples to b e pooled for optimal cost savings at various population prevalences, E stimated costs included technician time, laboratory consumables, and a ssay costs of testing pooled samples and retesting individual specimen s from presumptive positive pools: Estimation of population prevalence based on the pooled LCR results was also applied, After individual ur ine specimens were processed, 568 specimens were pooled by 4 into 142 poets and another 520 specimens were pooled by 10 into 52 pools. For c omparison, all 1,088 urine specimens were tested individually. The sam ple-to-cut-off ratio was lowered from 1.0 to 0.2 for pooled samples, a fter a pilot study which tested 148 samples pooled by 4 was conducted. The pooling algorithm was 100% (48 of 48) sensitive when samples were pooled by 4 and 98.4% (61 of 62) Sensitive when samples were pooled b y 10. Although 2.0% (2 of 99) of the negative pools of 4 and 7.1% (1 o f 14) of the negative pools of 10 tested presumptive positive, all sam ples in these presumptive-positive pools were negative when retested i ndividually, making the pooling algorithm 100% specific. In a populati on with 8% genital C. trachomatis prevalence, pooling by four would re duce costs by 39%. The model demonstrated that with a lower prevalence of 2%, pooling eight samples would reduce costs by 59%. Pooling urine samples for detection of C. trachomatis by LCR is sensitive, specific , and cost saving compared to testing individual samples.