Study objectives: (1) To identify factors predictive for gonorrhea and chlamydia positivity by LCR testing based on history and physical findings encountered during the sexual abuse evaluations. (2) To compare Ligase Chain Reaction (LCR), Polymerase Chain Reaction (PCR), and culture methods in the detection of chlamydia and gonorrhea infection among prepubertal and adolescent girls referred for sexual abuse evaluations.
Design: Prevalence odds ratios and logistic regression analysis were used to identify factors among patients' physical symptoms and signs, history of sexual activity, and abuse characteristics that were associated with positive test results for gonorrhea and chlamydia. The Kappa statistic was used to perform pairwise comparisons of LCR, PCR, and culture identification of gonorrhea and chlamydia infection.
Setting: A specialized sexual abuse clinic in San Antonio, Texas.
Participants: A consecutive sample of 229 girls between the ages of 6 and 20 who reported, or had indicators of, abusive genital-genital or genital-anal contact.
Main outcome measures: Patients' history and physical findings predicting positive test results for gonorrhea and chlamydia infection; and relative sensitivity of testing sites (vaginal swab and urine) and methodologies (LCR, PCR, and culture) in identifying gonorrhea and chlamydia infection.
Results: (1) Gonorrhea infection: 3.2% of subjects were positive for gonorrhea by LCR at one or more sites; 2.4% had positive gonorrhea cultures. There was excellent agreement between vaginal swab LCR and PCR; agreement between urine samples was limited by the small number of positive tests. The sole factor that predicted gonorrhea positivity was increased number of white blood cells seen on wet mount. (2) Chlamydia infection: 11.1% of subjects were positive for chlamydia by at least one LCR test; only 0.8% had positive chlamydia cultures. Both urine and vaginal swab testing showed good agreement between PCR and LCR but not between culture and either of the newer methodologies. Factors that predicted chlamydia positivity were: patient history of consensual sexual contact, patient history of vaginal discharge, and the presence of concerning or definitive findings of genital trauma.
Conclusions: While LCR, PCR, and culture techniques appeared comparable for detecting gonorrhea, LCR techniques detected significantly more patients with chlamydia infection when compared with the culture technique. PCR was comparable to LCR in detecting chlamydia infection. The LCR vaginal swab detected more patients with chlamydia and gonorrhea than the LCR urine sample. Risk factors for chlamydia and gonorrhea infection were present in most, but not all, of the children with positive LCR findings. LCR and PCR appear to detect more chlamydial and gonorrheal infections than do cultures.