Wednesday, March 12, 2008
An Internet-based screening program, www.iwantthekit.org, designed to educate and screen women for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG), offered home self-sampling kits.
To evaluate the performance of two NAATs used to detect CT and NG.
From July 2004 to October 2007, 995 self-collected vaginal swabs were tested for CT and NG by Becton-Dickinson ProbeTec™ SDA and Gen-Probe® APTIMA® Combo2 TMA. Vaginal swabs were self-obtained at home and mailed in a dry state to the laboratory for testing. Swabs were expressed in 800µl Tris-EDTA buffer; 200µl was placed into SDA diluent and 200µl was placed into TMA swab transport medium. All tests were conducted according to manufacturers' procedures. The gold standard for a CT or NG infected patient was defined as 2 positive NAATs. Discrepant samples were retested by the Gen-Probe® APTIMA® stand alone assay, ACT or AGC, or Roche PCR.
Of 995 swabs submitted, 91 were CT infected (9.1%), 14 NG infected (1.4%), and 7 of these were co-infected (0.7%). All CT and GC Combo2 positive/ProbeTec negative samples were confirmed as true positives by the alternative NAAT. CT: ProbeTec had a sensitivity and specificity of 81.3% (74/91) and 100% (904/904), respectively. Combo 2 had a sensitivity and specificity of 100% (91/91) and 100% (904/904), respectively. GC: ProbeTec had a sensitivity and specificity of 78.6% (11/14) and 100% (981/981), respectively. Combo 2 had a sensitivity and specificity of 100% (14/14) and 100% (981/981), respectively. Overall, ProbeTec had 17 CT false negative results (1.7%) and 3 NG false negative results (0.3%).
Our results indicated APTIMA® Combo2 was more sensitive than Becton-Dickinson ProbeTec™ for self-obtained vaginal swabs collected at home and transported in a dry state.
Self collected vaginal samples collected at home are suitable specimens for NAAT testing.