Evaluation of urine-based screening strategies to detect Chlamydia trachomatis among sexually active asymptomatic young males
Shafer, M.A.; Schachter, J.; Moncada, J.; Keogh, J.; Pantell, R.; Gourlay, L.; Eyre, S.; Boyer, C.B.
JAMA 270(17): 2065-2070
Objective: To evaluate the performances of diagnostic screening tests alone or in combination to detect asymptomatic chlamydial urethral infection in young males. Design: Comparisons of the performance profiles of the following chlamydia screening strategies were done: urethral culture; identification of polymorphonucleocytes (PMNs) on spun first-void urine (FVU); urinary leukocyte esterase test (LET) on unspun FVU; chlamydial enzyme immunoassay (EIA) applied to FVU sediment; combining LET on unspun FVU followed by EIA with or without direct fluorescent antibody (DFA) confirmation on FVU sediment; and combining PMNs on spun FVU followed by EIA with or without DFA confirmation. Setting: General clinics at a youth detention center, university-based teen clinic, college health service, and a military screening clinic. Patients: A total of 618 males aged 12 to 35 years (mean, 17 years) were recruited as a convenience sample; site participation rates ranged from 50% to 80%. Eligible subjects were sexually active, denied symptoms of urethritis, and had taken no antibiotics in the prior 2 weeks. Main Outcome Measures: Sensitivity, specificity, and positive and negative predictive values of each test strategy's ability to detect Chlamydia trachomatis infection, and cost to confirm each positive case. Results: With a 7% prevalence of chlamydial infection, tissue culture had a sensitivity of only 61 %. However, two strategies yielded significantly better performance profiles compared with the others: EIA confirmed by DFA test with a sensitivity of 84%, a specificity of 100%, and a cost to identify each positive case of 434; and PMNs followed by EIA confirmed by DFA test with a sensitivity of 78%, a specificity of 100%, and a cost to identify each positive case of 199. The LET followed by EIA-DFA had a similar performance profile to the PMN test strategies. Conclusions: A combination of a nonspecific screening of FVU for PMNs or LET followed by specific testing with EIA with DFA confirmation has superior clinical and cost-effective performance for detecting asymptomatic C. trachomatis urethritis in young males compared with other strategies. However, an evaluation of the medical, fiscal, and psychological benefits and risks associated with a specific screening strategy for sexually transmitted diseases must be made before adopting a specific strategy for a particular population.