The impact on accuracy and cost of ligase chain reaction testing by pooling urine specimens for the diagnosis of Chlamydia trachomatis infections.
OBJECTIVE
Nucleic acid amplification testing is the most accurate approach to diagnosing Chlamydia trachomatis infections. Our objective was to compare the accuracy and cost savings of pooling urines as opposed to individual testing.


METHODS
Strategies of pooling urine specimens into groups of four (4x pool) or eight (8x pool) followed by testing the positive pools individually were compared to individual specimen testing to determine if significant cost savingS could be realized without compromising the sensitivity and specificity 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 female (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% (48/49), respectively, when eight urines were pooled. Both pooling and individual testing strategies identified all the negative samples accurately. Cost 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 LCx system is a simple, accurate, and cost-saving approach that can significantly reduce the cost of amplified nucleic acid testing with minimal sacrifice of testing accuracy.
Krepel
J
J
Scilab Microbiology Services, Thornhill, Ontario, Canada.
Patel
J
J
Sproston
A
A
Hopkins
F
F
Jang
D
D
Mahony
J
J
Chernesky
M
M
D000293:Adolescent; D000328:Adult; D000465:Algorithms; D002690:Chlamydia Infections / Q000175:diagnosis* / Q000652:urine; D002692:Chlamydia trachomatis / Q000302:isolation & purification*; D017046:Cost Savings; D011088:DNA Ligases; D005260:Female; D005784:Gene Amplification; D006801:Humans; D008297:Male; D012680:Sensitivity and Specificity; D014556:Urine / Q000382:microbiology
D011088:DNA Ligases