title: External validation of the OHTS-EGPS model for predicting the 5-year risk of open-angle glaucoma in ocular hypertensives.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Public Health, Epidemiology and Biostatistics, University of Birmingham, , Birmingham, UK.
authors.forename: Yemisi
authors.initials: Y
authors.lastname: Takwoingi
authors.forename: Adriana P
authors.initials: AP
authors.lastname: Botello
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Burr
authors.forename: Augusto
authors.initials: A
authors.lastname: Azuara-Blanco
authors.forename: David F
authors.initials: DF
authors.lastname: Garway-Heath
authors.forename: Hans G
authors.initials: HG
authors.lastname: Lemij
authors.forename: Roshini
authors.initials: R
authors.lastname: Sanders
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: King
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Deeks
mesh_terms: D000959:Antihypertensive Agents; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D064887:Observational Studies as Topic; D009798:Ocular Hypertension / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D016016:Proportional Hazards Models; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012307:Risk Factors; D014065:Tonometry, Ocular
chemical_list: D000959:Antihypertensive Agents