Self-Collected Penile Swabs in a Clinic: How Do They Compare to Urethral Swabs for Accuracy for Detection of Neisseria Gonorrhoeae and Chlamydia Trachomatis?

Background: Urethral swabs are preferred for the culture of gonorrhea in males and are also used for the diagnosis of chlamydia. Self-collected penile swabs can be used for nucleic acid amplification tests (NAATs) in males, but have not been compared to clinician-collected urethral swabs.

Methods: Men who were being cultured for the diagnosis of gonorrhea in the STD clinic were asked to volunteer to also collect a penile swab for a NAAT for gonorrhea (GC) and chlamydia (CT).  Clinician-collected urethral swabs for GC culture/Gram stain were placed into transport media for a NAAT.  Volunteers for the study were then asked to collect penile swabs for transport media for the same NAAT assay. GC culture results for gonorrhea were also determined.

Results: In an ongoing study, of 92 men approached in the clinic, 83 (90.0%) of men agreed to collect a penile swab. From paired specimens, test results indicated 10 (12%) were positive for GC and 14 (16.8%) for CT from penile swabs; 9 (10.8%) were positive for GC and 12 (14.4%) for CT from clinician-collected urethral swabs. Results from penile swabs and urethral swabs agreed except 1 sample was penile+/urethral- for GC and 2 samples were penile+/urethral- for CT. There was no significant difference between self-collected penile swab and clinician-collected urethral swab for NAATs (p=0.500 for GC; p=0.250 for CT). Two of the three discordant samples positive by the penile swabs only were confirmed to be true positives by another NAAT assay (1 GC and 1/2 CT). Of the 10 positive GC NAAT results, all 10 were positive for GC by Gram stain and culture.

Conclusions: Self-collected penile swabs appeared to be as accurate as clinician-collected swabs for the detection of GC and CT for NAAT assays and could expedite express visits in a busy STD clinic.