Prevalance of pharyngeal,rectal and GU chlamydia and gonorrhea in a high risk urban youth MSM population: Urine screening alone significantly underestimates infections

Background: Neisseria gonorrhea (GC) and Chlamydia trachomatis (CT) are the two most common sexually transmitted infections (STIs) in the United States. Around 85% are asymptomatic, and highest incidence is in patients 15 to 24y of age. Prevalence of gonococcal and chlamydial infections varies by site with rectal and pharyngeal sites serving as important reservoirs for infection that might otherwise be missed by urine screen alone. Methods: We analyzed GC/CT nucleic acid amplification tests (NAAT) on urine, pharyngeal and rectal specimens from an adolescent MSM population (14- 24 years). Results: Of 117 patients tested, 46 were positive at one or more sites for gonorrhea, chlamydia or both. For CT - urine, rectal and pharyngeal testing detected 2 (1.7%), 11 (7.6%) and 2 (1.7%) cases respectively. For GC - urine, rectal and pharyngeal testing detected 9 (7.6%); 18 (15%) and 18(15%) cases respectively. Urine testing alone missed 86% of CT infections and 70% of GC infections, while rectal testing alone missed only 21% of CT infections and 38% of GC infections. Pharyngeal testing alone missed 78% of CT infection and 38% of GC infections. Conclusion: In this high risk population, asymptomatic infections may contribute to high burden of existing disease. Triple screening (urine, throat and rectum) by NAAT can enhance detection of infected individuals by approximately 60%. Notably, rectal screening appeared to have the highest yield, significantly more than urine screening. Further studies are needed to determine best screening strategies in other high risks youth groups such as MSM and HIV+ adolescents.