The impact on accuracy and cost of ligase chain reaction testing by pooling urine specimens for the diagnosis of Chlamydia trachomatis infections

Background and Objectives: Nucleic acid amplification testing is the most a ccurate approach to diagnosing Chlamydia trachomatis infections. Our object ive was to compare the accuracy and cost savings of pooling urines as oppos ed to individual testing. Study Design: Strategies of pooling urine specimens into groups of four (4x pool) or eight (8x pool) followed by testing the positive peals individual ly were compared to individual specimen testing to determine if significant cost savings could be realized without compromising the sensitivity and sp ecificity of the LCx C. trachomatis Assay (Abbott Laboratories, Abbott Park , Chicago, IL) performed in a busy private medical laboratory. Results: A total of 1,220 patient urine samples, 1,187 male (97%) and 33 fe male (3%), were tested using the normal LCx specimen to cutoff ratio (S/CO) of 1.0 and a decreased S/CO value of 0.2. Individual testing identified 98 .2% (109/111) of positive urines. The 4x pooling maneuver identified 92.8% (103/111) of positive patients with the regular cutoff and 96.4% (107/111) when the cutoff was decreased. These values were 95.9% (47/49) and 97.9% (4 8/49), respectively, when eight urines were pooled. Both pooling and indivi dual testing strategies identified all the negative samples accurately. Cas t savings of pooling were calculated to be 44.5% for pools of four and 37.5 % for pools of eight, applying the lowered cutoff. Conclusions: Pooling urine specimens for testing with the C. trachomatis LC x system is a simple, accurate, and cost-saving approach that can significa ntly reduce the cost of amplified nucleic acid testing with minimal sacrifi ce of testing accuracy.