Validity of Optical Coherence Tomography as a Diagnostic Method for Diabetic Retinopathy and Diabetic Macular Edema

To validate optical coherence tomography (OCT) for the diagnosis of referable retinopathy (severe, very severe or proliferative retinopathy, and macular edema) in diabetic patients. We performed a cross-sectional observational study. A random sample was analyzed comprising 136 eyes of diabetic patients referred to the hospital in Elche (Spain) with suspected referable retinopathy between October 2012 and June 2013. Primary variable: Referable retinopathy measured by ophthalmological examination of the retina. OCT data included: central foveal thickness, presence of intraretinal fluid, and fundus photographs. The receiver operating characteristic (ROC) curve was calculated to determine the minimum thickness value with a positive likelihood ratio >10. To determine the validity of OCT, the following diagnostic test was defined: Positive: if the patient had at least 1 of these criteria: foveal thickness greater than the point obtained on the previously defined ROC curve, intraretinal fluid, abnormal fundus photographs; Negative: none of the above criteria. Sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, and Kappa statistic were determined. Of the 136 eyes, 48 had referable retinopathy (35.3%, 95% confidence interval [CI]: 27.3-43.3). The minimum thickness value with a positive likelihood ratio >10 was 275 μm. The diagnostic test constructed showed: sensitivity, 91.67% (95% CI: 79.13-97.30); specificity, 93.18% (95% CI: 85.19-97.20); positive predictive value, 88.00% (95% CI: 75.00-95.03); negative predictive value, 95.35% (95% CI: 87.87-98.50); positive likelihood ratio, 13.44 (95% CI: 6.18-29.24); negative likelihood ratio, 0.09 (95% CI: 0.03-0.23). The Kappa value was 0.84 (95% CI: 0.75-0.94, P < 0.001. This study constructed a diagnostic test for referable diabetic retinopathy with type A evidence. Nevertheless, studies are needed to determine the validity of this test in the general diabetic population.