Use of ligase chain reaction and polymerase chain reaction on urine specimens to detect Chlamydia trachomatis infections in a sexually transmitted diseases clinic in Singapore.

This study was done to assess the specificity and sensitivity of the DNA amplification assays of ligase chain reaction (LCR) and polymerase chain reaction (PCR) on urine specimens to detect Chlamydia trachomatis infections in both male and female patients seen at a sexually transmitted diseases (STD) clinic in Singapore, compared with other diagnostic methods currently in use. A total of 100 patients were selected; 50 male patients diagnosed with non-gonococcal urethritis based on symptoms and a positive Gram-stained urethral smear and 50 female asymptomatic sex workers were assessed. Automated assays using LCR and PCR were used, and compared to enzyme immunoassays, chlamydial cell cultures and PCR of urethral and endocervical swab specimens. In male patients, LCR and PCR of urine specimens had sensitivities of 100%, compared to 87.0% for PCR of urethral swab specimen, 82.6% for enzyme immunoassay (EIA) and 91.3% for cell cultures. In female patients, LCR and PCR of urine samples achieved sensitivities of 77.8% and 88.9% respectively, compared with 55.6% for PCR of endocervical swab specimens, 22.2% for EIA and 66.7% for cell cultures. LCR and PCR of urine samples provided higher sensitivity compared to cell cultures, EIA and PCR of urethral and endocervical swab specimens. The use of LCR and PCR on urine as a non-invasive means of detecting chlamydial infections is viable, and may have a role to play in population-based screening programmes.

Molecular detection of human immunodeficiency virus-1 infection among commercial sex workers using the polymerase chain reaction in Singapore.

We studied the sensitivity of polymerase chain reaction (PCR) for detecting early human immunodeficiency virus-1 (HIV-1) in sex workers. Blood samples of sex workers who attended our Sexually Transmitted Diseases clinic were tested for HIV infection by testing for the presence of HIV antibody and HIV-1 proviral DNA using PCR (with the Amplicor HIV-1 amplification kit, Roche) at 00 (when they first register to work as sex workers), 01 and 03 months after starting work. The objective was to detect HIV-1 using PCR in sex workers during the "window" period when their HIV antibody tests were still negative. Sixty-nine blood samples were PCR-tested at 00 month of which 8 were simultaneously positive for HIV antibody and PCR tests. Seventy-seven blood samples were tested at 03 month. We found that PCR test using the Amplicor HIV-1 amplification kit (Roche) to be sensitive in detecting HIV infection in sex workers but the test appeared not sensitive enough to detect HIV-1 infection during the "window" period. We were unable to detect any sex workers with PCR detectable HIV-1 before they seroconverted to become HIV antibody positive. The reason for the failure was attributed to the low infection rate among sex workers and possible lack of sensitivity of the Amplicor PCR/HIV-1 amplification kit to detect early HIV-1 infection. We are currently studying other PCR procedures to improve the sensitivity of the PCR test for HIV-1.