Proctitis in gay and bisexual men. Are microscopy and proctoscopy worthwhile?

We explored the association between nucleic acid amplification testing (NAAT) and rectal microscopy/proctoscopy findings and correlates of rectal STIs among 150 gay and bisexual men (GBM) diagnosed with proctitis at the Sydney Sexual Health Centre from March 2016 to October 2017.

From case files, we analysed risk behaviours, microscopy, proctoscopy and NAAT results for rectal STIs (Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, herpes simplex virus type 1/2, lymphogranuloma venereum and syphilis). χ² test assessed the association between microscopy/proctoscopy findings and NAAT results. Linear regression assessed the association between NAAT positivity and correlates of rectal STIs.

The mean age was 32.5 (9.8) years, 43% (65/150) were taking pre-exposure prophylaxis, 17% (26/150) were HIV positive and 24% (36/147) had multiple rectal STIs.Among GBM with documented proctoscopy findings (n=113), 58% (65/113) had discharge, 36% (41/113) had anorectal erythema and 25% (28/113) had bleeding. A quarter of GBM (28/113) had negative proctoscopy findings.Discharge found on proctoscopy (p=0.001), positive HIV status (p=0.030) and time since last receptive anal intercourse (p=0.028) were independently associated with NAAT positivity for any rectal STI. Discharge had a positive likelihood ratio of 1.6 (95% CI 1.0 to 2.4).Among those with documented microscopy findings (n=69), 59% (41/69) and 41% (28/69) were NAAT positive and negative, respectively. Among NAAT-positive GBM, 27 (66%) had polymorphonuclear cells (PMNs) (mean number of PMNs, 10 (SD 9) cells per oil immersion field), 1 (2%) had Gram-negative intracellular diplococci and 11 (27%) had negative findings. There was no significant association between microscopy findings and NAAT results (p=0.651) or the number of rectal STI (p=0.279).

Microscopy does not reliably provide information necessary to tailor the management of GBM diagnosed with proctitis. Discharge found during proctoscopy may identify GBM with rectal STI. Services should consider recommendations to perform these investigations.