Value of light microscopy to diagnose urogenital gonorrhoea: a diagnostic test study in Indonesian clinic-based and outreach sexually transmitted infections services

Introduction

Gonorrhoea is a common sexually transmitted disease caused by Neisseria gonorrhoeae (Ng) infection. Light microscopy of urogenital smears is used as a simple tool to diagnose urogenital gonorrhoea in many resource-limited settings. We aimed to evaluate the accuracy of light microscopy to diagnose urogenital gonorrhoea as compared with a PCR-based test.

Methods

In 2014, we examined 632 male urethral and 360 endocervical smears in clinic-based and outreach settings in Jakarta, Yogyakarta and Denpasar, Indonesia. Using the detection of Ng DNA by a validated PCR as reference test, we evaluated the accuracy of two light microscopic criteria to diagnose urogenital gonorrhoea in genital smears: (1) the presence of intracellular Gram-negative diplococci (IGND) and (2) ≥5 polymorphonuclear leucocytes (PMNL)/oil-immersion field (oif) in urethral or ≥20 PMNL/oif in endocervical smears.

Results

In male urethral smears, IGND testing had a sensitivity (95% CI), specificity (95% CI) and kappa±SE of 59.0% (50.1 to 67.4), 89.4% (86.3 to 91.9) and 0.49±0.04, respectively. For PMNL count, these were 59.0% (50.1 to 67.4), 83.7% (80.2 to 86.9) and 0.40±0.04, respectively. The accuracy of IGND in the clinic-based settings (72.0% (57.5 to 83.3), 95.2% (91.8 to 97.5) and 0.68±0.06, respectively) was better than in the outreach settings (51.2% (40.0 to 62.3), 83.4% (78.2 to 87.8) and 0.35±0.06, respectively). In endocervical smears, light microscopy performed poorly regardless of the setting or symptomatology, with kappas ranging from –0.09 to 0.24.

Conclusion

Light microscopy using IGND and PMNL criteria can be an option with moderate accuracy to diagnose urethral gonorrhoea among males in a clinic-based setting. The poor accuracy in detecting endocervical infections indicates an urgent need to implement advanced methods, such as PCR. Further investigations are needed to identify the poor diagnostic outcome in outreach services.

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