Antenatal Urine Samples Screened for Chlamydia

Urine samples from pregnant women have been successfully screened to identify those infected with Chlamydia trachomatis.

The urine screening was conducted using a commercial molecular assay utilizing target capture for the in vitro qualitative detection and differentiation of ribosomal RNA (rRNA) of C. trachomatis and Neisseria gonorrhoeae.

Scientists at University of Texas Southwestern Medical Center, (Dallas, TX, USA), tested a total of 2,018 pregnant women whose mean age was 26.9 years old, and of whom 84% were Hispanic. For four months, all women who were seen at a group of family planning and obstetric complication clinics in the area and who were between 35 and 37 weeks pregnant were tested. Both urine samples and endocervical secretions were assayed.

All samples were analyzed using the Aptima Combo 2 Assay, which is a target amplification nucleic acid probe test. The prevalence of Chlamydia according to tests of cervical secretions was 4.3% compared to 4.1% using urine sampling. The results from the two samplings were considered to be almost perfectly concordant. Sensitivity of urine screening was 96.5% relative to endocervical screening where the 95% confidence interval (CI) was 90.1% to 99.3%, with a relative specificity of 100%.

Urine screening for Chlamydia has shown to be accurate in male and nonpregnant female populations using Aptima Combo 2 Assay (Gen-Probe Inc.; San Diego, CA, USA). However, the scientists were uncertain that would translate to effectiveness in pregnant women. Their concern was that pregnant women might have amplification inhibitors not present in the nonpregnant population leading to nucleic acid amplification tests being less sensitive when performed on urine as compared with cervical specimens. However, this proved not to be the case.

Scott W. Roberts, MD, lead author of the study, said, "Removing the need for a speculum examination with its potential benefits in costs and respect for patients' desires has led us to use urine nucleic acid amplification testing for our C. trachomatis screening in all pregnant women." Urine sampling is also considerably cheaper than endocervical sampling, and scores points with patients who would rather not undergo an invasive exam. Chlamydia trachomatis is the most common bacterial sexually transmitted infection in the US. This disease disproportionately affects adolescent minority women, and untreated infection can lead to lasting reproductive tract morbidity. The study was published in the April 2011, edition of Obstetrics & Gynecology.

Related Links:
University of Texas Southwestern Medical Center
Gen-Probe Incorporated