Screening for Chlamydia Trachomatis in Young Men by Ligase Chain Reaction

Routine screening for Chlamydia trachomatis in men provides an accurate estimate of the disease prevalence and enhances control and prevention programs in that C. trachomatis is one of the most common sexually transmitted diseases (STD) among adolescents and young adults in the United States.1C. trachomatis infection among men has been underestimated because of noncompliance of asymptomatic men with screening programs to avoid the discomfort of urethral swab specimen collection. The rapid diagnostic test, LCx C. trachomatis Assay (Abbott Laboratories, Abbott Park, IL), which uses ligase chain reation (LCR) amplification technology to detect plasmid DNA from C. trachomatis in urine samples, is a noninvasive screening method.1-6 We report our experience using LCx to determine the prevalence and risk factors for C. trachomatis infection among young men seeking care at a health clinic in New York City. Methodology. From February to June 1997, screening for C. trachomatis by urine testing was offered to all men attending the Young Men's Clinic, an outpatient clinic of New York Presbyterian Hospital (Columbia campus) in New York City. The clinic's standardized data collection forms were used to assess risk factors. This study was approved by the Institutional Review Board for pediatric and adult subjects. The first 20 to 50 ml of the subjects' urine was processed according to the manufacturer's guidelines including recommendations for minimizing cross-contamination of specimens by barrier pipet tips and a dedicated work area. Positive samples were repeated for verification, and supplemental testing of all urine samples was done by Abbott Laboratories with the use of an LCR directed against the major outer membrane protein of C. trachomatis when specimens met the cutoff requirment for processing.7 Cultures were not performed. According to current Young Men's Clinic practice men considered at "high risk" for an STD (e.g. multiple sexual partners, previous history of an STD, unprotected sexual intercourse, history of signs or symptoms and an exposure to an STD) had traditional testing with urethral swabs for C. trachomatis by the Gen-Probe PACE 2 assay (Gen-Probe Inc., San Diego, CA). Men with signs or symptoms of an STD or an exposure history were given empiric antibiotic therapy. Partners of men with STD-related complaints or men who tested positive by either method were referred for testing and treatment. Univariate analysis using chi square and Student t tests were used to determine significant (P < 0.05) risk factors associated with infection in the 253 men who reported sexual activity. Results. The majority of the eligible subjects (302 of 304 men) participated in the study. One subject provided an inadequate volume of urine and was excluded. The mean age of the study population was 20 years (range, 13 to 33 years) and 73% were Hispanic. By age 17, 91% of the patients were sexually active. The stated reasons for the clinic visit were: general physical examination (56%); an STD-related complaint (33%); medical follow-up (6%); and HIV counseling and testing (5%). The prevalence of C. trachomatis in this population as determined by LCx was 8% (24 of 301). However, the prevalence among the 90 high risk study subjects was 2-fold higher; 15.5% (14 of 90) had positive tests using PACE 2, and 18.8% (17 of 90) had positive tests using LCx (Table 1).TABLE 1: Comparison of LCx vs. Gen-Probe PACE 2 test results* As others have reported, risk factors significantly associated with a positive LCx test were a self-reported history of an STD [odds ratio (OR), 3.61; 95% confidence interval (CI95), 1.45 to 8.98; P < 0.006] and a known exposure to an STD (OR 3.75; CI95 1.40 to 10.06; P < 0.01). A previously unreported risk marker, impregnating a woman, was significantly associated with C. trachomatis in this study population (OR 4.16; CI95 1.53 to 11.3; P < 0.005). Increasing age was not associated with infection.8 Discussion. Urine testing with LCx is highly acceptable and can improve estimates of chlamydial infection among men by detecting asymptomatic cases.9 LCx has been shown to be highly sensitive, but this study design, sample size and small prevalence of infection limit our ability to calculate the sensitivity and specificity of LCx. Problems with LCx testing include detection of nonviable organisms and need to refrigerate urine samples. The prevalence of C. trachomatis in our population was 8% (24 of 301) which is comparable with the mean prevalence of 9.5% reported in men utilizing non-STD clinics in the US between 1984 and 1997.10-14 Common risk factors for STDs such as young age, early age of sexual activity and greater number of sexual partners were not statistically associated with a positive LCx test for C. trachomatis in this study. A known exposure to an STD and history of an STD were significantly associated with C. trachomatis infection. Although 20% of the sexually active young men had signs or symptoms of an STD, symptoms did not predict a positive LCR test. In our study pregnancy in a sexual partner was found to be a novel risk marker. Our data suggest that impregnating a partner is a proxy for unprotected sex and may identify young men at increased risk for C. trachomatis infection. We have previously performed a study of risk factors for C. trachomatis in women in the same community and found that pregnancy was a risk factor.15 These results highlight the importance of counseling and testing for STDs in women and men of child-bearing age. Acknowledgment. We thank Abbott Pharmaceuticals for their financial support. Natalie Neu, M.D. Surah Grumet, M.P.H. Alex McNees, M.P.H. Lena Lai, B.A. Phyllis Della-Latta, Ph.D., F.A.A.M. Susan Whittier, Ph.D. Lisa Saiman, M.D., M.P.H. Departments of Pediatrics (NN, SG, AM, LS) and Pathology (PDL, SW); Columbia University; New York, NY