the sensitivity, specificity and predictive values of snellen chart compared to the diagnostic test in amblyopia screening program in iran

introduction amblyopia is a leading cause of visual impairment in both childhood and adult populations. our aim in this study was to assess the epidemiological characteristics of the amblyopia screening program in iran. materials and methods a cross-sectional study was done on a randomly selected sample of 4,636 iranian children who were referred to screening program in 2013 were participated in validity study, too. from each provinces the major city were selected. screening and diagnostic tests were done by instructors in first stage and optometrists in second stage, respectively. finally data were analyzed by stata version 13. results the sensitivity was ranged from 74% to 100% among the various provinces such that fars and ardabil province had maximum and minimum values, respectively. the pattern of specificity was differ and ranged 44% to 84% among the provinces; hormozgan and fars had maximum and minimum values, respectively. the positive predictive value was also ranged from 35% to %81 which was assigned to khuzestan and ardabil provinces, respectively. the range of negative predictive value was 61% to 100% which was belonged to ardabil and fars provinces. conclusion the total sensitivity (89%) and negative predictive values (93%) of screening test among children aged 3-6 years is acceptable, but only 51% of children refereed to second stage are true positive and this imposes considerable cost to health system.