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External validation of the OHTS-EGPS model for predicting the 5-year risk of open-angle glaucoma in ocular hypertensives
  1. Yemisi Takwoingi1,
  2. Adriana P Botello2,
  3. Jennifer M Burr3,
  4. Augusto Azuara-Blanco4,
  5. David F Garway-Heath5,
  6. Hans G Lemij6,
  7. Roshini Sanders7,
  8. Anthony J King8,
  9. Jonathan J Deeks1,
  10. for the Surveillance for Ocular Hypertension Study Group
  1. 1Department of Public Health, Epidemiology and Biostatistics, University of Birmingham, Birmingham, UK
  2. 2Aberdeen Royal Infirmary, Aberdeen, UK
  3. 3School of Medicine, University of St Andrews, St Andrews, UK
  4. 4Centre for Vision and Vascular Science, Queen's University Belfast, Belfast, UK
  5. 5NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, UK
  6. 6Glaucoma Services, Rotterdam Eye Hospital, Rotterdam, The Netherlands
  7. 7Queen Margaret Hospital, Dunfermline, UK
  8. 8Department of Ophthalmology, Queen's Medical Centre, University Hospital, Nottingham, UK
  1. Correspondence to Dr Yemisi Takwoingi, Department of Public Health, Epidemiology and Biostatistics, University of Birmingham, Birmingham B15 2TT, UK; y.takwoingi{at}bham.ac.uk

Abstract

Aims To independently evaluate and compare the performance of the Ocular Hypertension Treatment Study-European Glaucoma Prevention Study (OHTS-EGPS) prediction equation for estimating the 5-year risk of open-angle glaucoma (OAG) in four cohorts of adults with ocular hypertension.

Methods Data from two randomised controlled trials and two observational studies were analysed individually to assess transferability of the prediction equation between different geographical locations and settings. To make best use of the data and to avoid bias, missing predictor values were imputed using multivariate imputation by chained equations. Using the OHTS-EGPS risk prediction equation, predicted risk was calculated for each patient in each cohort. We used the c-index, calibration plot and calibration slope to evaluate predictive ability of the equation.

Results Analyses were based on 393, 298, 188 and 159 patients for the Rotterdam, Moorfields, Dunfermline, and Nottingham cohorts, respectively. The discriminative ability was good, with c-indices between 0.69 and 0.83. In calibration analyses, the risk of OAG was generally overestimated, although for the Rotterdam cohort the calibration slope was close to 1 (1.09, 95% CI 0.72 to 1.46), the ideal value when there is perfect agreement between predicted and observed risks.

Conclusions The OHTS-EGPS risk prediction equation has predictive utility, but further validation in a population-based setting is needed.

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