The Accuracy and Clinical Application of Predictive Models for Primary Open-Angle Glaucoma in Ocular Hypertensive Individuals
Presented at: American Academy of Ophthalmology Annual Meeting, November 2006, Las Vegas, Nevada.
Received 3 April 2008; received in revised form 22 May 2008; accepted 26 June 2008. published online 18 September 2008.
Objective
This report compares the accuracy of 3 prediction models for the development of primary open-angle glaucoma (POAG). The models differ primarily in their handling of these eye-specific variables: intraocular pressure (IOP), central corneal thickness (CCT), vertical cup-to-disc ratio (VCD), and visual field pattern standard deviation (PSD). The “means” model includes age and the means of right and left eyes; the “means plus asymmetry” model includes age, the means of right and left eyes as well as the absolute difference between eyes for eye-specific variables; and the “worse” eye model includes age and values from the eye at higher risk for developing POAG.
Design
This report uses data from the observation group of the Ocular Hypertension Treatment Study (OHTS) and the placebo group of the European Glaucoma Prevention Study (EGPS) who have complete data on both eyes at baseline. Performance of the prediction models is assessed using the c-statistic, calibration chi-square, and Pearson correlation coefficient.
Participants
The OHTS observation group (n = 717; 6.7 years median follow-up) and the EGPS placebo group (n = 324; 4.9 years median follow-up).
Testing
Baseline data included demographic characteristics, medical history, ocular examination, visual fields, and optic disc photographs.
Main Outcome Measures
Development of reproducible visual field abnormality or optic disc deterioration as determined by masked readers and attributed to POAG by a masked end point committee.
Results
Baseline factors that were statistically significant in all predictive models were age, IOP, CCT, VCD, and PSD. Also, statistically significant were baseline asymmetry in IOP and asymmetry in VCD. The c-statistics for the “means” model, “means plus asymmetry” model, and “worse” eye model were 0.74, 0.77, and 0.75, respectively. The calibration chi-square values were 7.32, 11.19, and 1.81, respectively. Correlation coefficients between risk estimates calculated by different models ranged from 0.94 to 0.98.
Conclusions
The high agreement between the risk estimates from 3 different predictive models for the development of POAG suggests little difference in their statistical or clinical performance. The predictive model that uses the means of both eyes for eye-specific variables is the simplest to use and the most robust to measurement variability and error.
Financial Disclosure(s)
The authors have no proprietary or commercial interest in any materials discussed in this article.
Available online: September 18, 2008.
Manuscript no. 2008-431.
1 Washington University, St. Louis, Missouri.
2 Istituto di Ricerche Farmacologiche “Mario Negri”, Milan, Italy.
3 Policlinico di Monza University of Milano-Bicocca, Milan, Italy.
4 Merck Research Laboratories, Blue Bell, Pennsylvania.
Writing Committee: Mae O. Gordon, PhD,1 Michael A. Kass, MD,1 Valter Torri, MD,2 Stefano Miglior, MD,3 Julia A. Beiser, MS,1 Irene Floriani, PhD,2 J. Philip Miller, AB,1 Feng Gao, PhD,1 Ingrid Adamsons, MD, MPH,4 Davide Poli, ScD2
A complete list of personnel is available at https://vrcc.wustl.edu. Accessed March 18, 2008.
Financial Disclosure(s): The authors have no proprietary or commercial interest in any materials discussed in this article.
Supported by awards from the National Eye Institute, the National Center on Minority Health and Health Disparities, National Institutes of Health (grants EY09341, EY09307), awards to the Department of Ophthalmology and Visual Sciences at Washington University, the NIH Vision Core Grant P30 EY 02687, awards to the Department of Ophthalmology at University of Miami, the NIH Vision Core Grant P30 EY 01480; the European Commission BMH4-CT-96-1598; Merck Research Laboratories, White House Station, New Jersey; Pfizer, Inc., New York, New York and unrestricted grants from Research to Prevent Blindness, Inc., New York, New York.
Correspondence:
Mae O. Gordon, PhD, OHTS Coordinating Center, Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Box 8203, 660 South Euclid, St. Louis, MO 63110. E-mail: mae@vrcc.wustl.edu
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