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Original article
Comparison of two Gram stain point-of-care systems for urogenital gonorrhoea among high-risk patients: diagnostic accuracy and cost-effectiveness before and after changing the screening algorithm at an STI clinic in Amsterdam
  1. M Bartelsman1,
  2. M Straetemans2,
  3. K Vaughan3,
  4. S Alba2,
  5. M S van Rooijen1,4,5,
  6. W R Faber1,6,
  7. H J C de Vries1,6,7
  1. 1STI Outpatient Clinic, Public Health Service of Amsterdam (GGD Amsterdam), Amsterdam, The Netherlands
  2. 2Department of Biomedical Research, Royal Tropical Institute, Amsterdam, The Netherlands
  3. 3Department of Development Policy and Practice, Royal Tropical Institute, Amsterdam, The Netherlands
  4. 4Department of Research, Public Health Service of Amsterdam (GGD Amsterdam), Amsterdam, The Netherlands
  5. 5Public Health Laboratory, Public Health Service of Amsterdam (GGD Amsterdam), Amsterdam, The Netherlands
  6. 6Department of Dermatology, Academic Medical Center (AMC), University of Amsterdam, Amsterdam, The Netherlands
  7. 7Center for Infection and Immunology Amsterdam (CINIMA), Academic Medical Center (AMC), University of Amsterdam, Amsterdam, The Netherlands
  1. Correspondence to Professor Henry de Vries, Public Health Service of Amsterdam (GGD Amsterdam), Cluster of Infectious Diseases, STI Outpatient Clinic, Weesperplein 1, 1018 WZ Amsterdam, The Netherlands; h.j.devries{at}amc.nl

Abstract

Objectives To compare point-of-care (POC) systems in two different periods: (1) before 2010 when all high-risk patients were offered POC management for urogenital gonorrhoea by Gram stain examination; and (2) after 2010 when only those with symptoms were offered Gram stain examination.

Methods Retrospective comparison of a Gram stain POC system to all high-risk patients (2008–2009) with only those with urogenital symptoms (2010–2011) on diagnostic accuracy, loss to follow-up, presumptively and correctly treated infections and diagnostic costs. Culture was the reference diagnostic method.

Results In men the sensitivity of the Gram stain was 95.9% (95% CI 93.1% to 97.8%) in 2008–2009 and 95.4% (95% CI 93.7% to 96.8%) in 2010–2011, and in women the sensitivity was 32.0% (95% CI 19.5% to 46.7%) and 23.1% (95% CI 16.1% to 31.3%), respectively. In both periods the overall specificity was high (99.9% (95% CI 99.8% to 100%) and 99.8% (95% CI 99.7% to 99.9%), respectively). The positive predictive value (PPV) and negative predictive value (NPV) before and after 2010 were also high: PPV 97.0% (95% CI 94.5% to 98.5%) and 97.7% (95% CI 96.3% to 98.6%), respectively; NPV 99.6% (95% CI 99.4% to 99.7%) and 98.8% (95% CI 98.5% to 99.0%), respectively. There were no differences between the two time periods in loss to follow-up (7.1% vs 7.0%). Offering Gram stains only to symptomatic high-risk patients as opposed to all high-risk patients saved €2.34 per correctly managed consultation (a reduction of 7.7%).

Conclusions The sensitivity of the Gram stain is high in men but low in women. When offered only to high-risk patients with urogenital symptoms, the cost per correctly managed consultation is reduced by 7.7% without a significant difference in accuracy and loss to follow-up.

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