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C. Liu, Vision in Preschoolers Study Group; Children Unable to Perform Screening Tests in the Vision in Preschoolers (VIP) Study: Results on the Gold Standard Examination and Impact on Sensitivity and Specificity . Invest. Ophthalmol. Vis. Sci. 2006;47(13):698.
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To examine the implications of the choices for classifying children who are unable to perform preschool vision screening tests.
During Phase II of the VIP Study, trained nurse and lay screeners each administered the Lea Symbols VA test, Stereo Smile II test, Retinomax Autorefractor, and SureSight Vision Screener to1475 children who later received a gold standard eye (GSE) examination to identify amblyopia, strabismus, significant refractive error, and unexplained reduced visual acuity. The outcome of the GSE for children whom screeners were unable to obtain screening test results (Unables) was compared to the outcomes of children who passed and children who failed each screening test. Estimates of sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were compared under 2 methods of incorporating Unables into the results of screening: 1) classifying Unables as screening failures, and 2) classifying the Unables as screening passers.
The proportion of VIP children who were Unable was ≤2% for each screening test. The GSE failure rate for Unables was 2 or more times the rate for screening passers for all tests (p<0.05 for all tests except Retinomax administered by nurses and Stereo Smile II administered by lay screeners). The proportion of Unables with the most severe conditions (Group 1) was similar to the proportion among screening failures for the Lea Symbols VA test, Retinomax, and SureSight. Relative to treating Unables as screening passers, treating Unables as screening failures increased the estimate of sensitivity by 1 to 9% (depending on test) and decreased the estimate of specificity by 0 to 2%; PPV decreased by 0 to 2% for most tests while NPV increased by 0 to 1 %.
Preschool children who are unable to perform VIP screening tests are more likely to have vision disorders than children who pass the tests. Because ≤2% of children are unable to do each test, referring these children for an eye examination has little impact on the PPV and NPV of the tests.
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