Point-of-care management of urogenital Chlamydia trachomatis via Gram-stained smear analysis in male high-risk patients. Diagnostic accuracy and cost-effectiveness before and after changing the screening indication at the STI Clinic in Amsterdam.

OBJECTIVES: To measure the effect of changing the point-of-care (POC) testing algorithm of urogenital chlamydia for all male high-risk patients to those with only symptoms with respect to: diagnostic accuracy, loss to follow-up, correctly managed consultations and costs.

METHODS: Retrospective comparison of the diagnostic accuracy and cost-effectiveness of Gram-stained urethral smear analysis for the POC management of urogenital Chlamydia trachomatis infections. Between 2008 and 2009 Gram-stained urethral smear analysis was offered to all men irrespective of symptoms; between 2010 and 2011 only to those with symptoms. The Aptima CT assay was the reference diagnostic test.

RESULTS: The number of examined Gram-stained smears in the two periods was respectively 7185 (2008-2009 period) and 18,852 (2010-2011 period). The sensitivity of the Gram stain analysis was respectively 83.8% (95% CI 81.2% to 86.1%) and 91.0% (95% CI 89.5% to 92.3%) (p<0.001). The specificity was respectively 74.1% (95% CI 73.0% to 75.2%) and 53.1% (95% CI 51.8% to 54.4%) (p<0.001). The positive predictive value was low in both periods, respectively 31.7% (95% CI 29.8% to 33.6%) and 35.6% (95% CI 34.1% to 37.1%) (p=0.002), whereas the negative predictive value was high, respectively 97.0% (95% CI 96.4% to 97.4%) and 95.4% (95% CI 94.6% to 96.1%) (p=0.002). The loss to follow-up rate between 2008-2009 and 2010-2011 was, respectively, 1.8% (95% CI 1.0% to 2.9%) vs 2.3% (95% CI 1.7% to 3.0%) (p=0.36). There was a small difference in overtreatment, 68.0% (95% CI 66.0% to 69.8%) vs 64.1% (95% CI 62.6% to 65.5%) (p=0.001). The cost per correctly managed consultation was 14.3% lower in the 2010-2011 period (€94.31 vs €80.82). The percentage of delayed treated infections was significantly lower in the 2008-2009 period (10.5%) compared with the 2010-2011 period (22.8%) (p<0.001).

CONCLUSIONS: With a high sensitivity in male high-risk patients, the Gram-stained urethral smear is a useful POC test to detect urogenital C. trachomatis. When offered only to men with urogenital symptoms the specificity decreases but the cost per correctly managed consultation is reduced with 14.3% without a significant difference in loss to follow-up but with a significantly higher rate of delayed treatment.