Valoración del uso de retinografía como método de diagnóstico precoz de glaucoma crónico en atención primariavalidación para el cribado en población con factores de riesgo

Abstract

• INTRODUCTION Glaucoma is an optic neuropathy characterized by morphological ocular changes and alterations in visual functions. Rapid diagnosis is necessary to initiate treatment to halt the advance of glaucoma towards blindness. • HYPOTHESIS. The use of digital papillary images captured in primary care settings using non-mydriatic retinography can be a useful test for glaucoma screening. • AIM: To determine the accuracy and behaviour of the retinography images taken at primary health care centres and interpreted by general practitioners, as a tool for diagnosing glaucoma. • MATERIAL AND METHOD: a. Design. This is an observational, descriptive and cross-sectional study with blind evaluation by two doctors working in parallel at a primary health care centre, as well as an ophthalmologist. The two doctors analysed the optic papillaries captured via retinography, evaluating any suspicious signs that might indicate glaucoma, and the measurements according to the cup-to-disc ratio (CDR). The ophthalmologist used the reference tests to diagnose glaucoma: measurement of interocular pressure (IOP), field of vision, gonioscopy and biomicroscopy with a Goldmann lens b. Sample: study subjects. Patients listed in the Diabetes Assistance Programme. Hi. inclusion criteria. • Diagnosed with Diabetes Mellitus. ® Diagnosed with hypertension. • Aged between 40 and 70. iv. Exclusion criteria. • Unable to undergo the diagnostic tests. • Previously diagnosed with glaucoma and/or diabetic retinopathy. a. Sampling and study framework. The sample size (n= 196 patients) was fixed according to the expected concordance rate agreed on between the primary health care doctors and the ophthalmologist, estimating the level of disagreement to be around 15%, with an accuracy of 5% for a confidence interval of 95%. b. Variables. The study variable was the diagnosis of glaucoma. The descriptive study of the sample considered age, gender, the time of evolution and treatment of the diabetes, other ophthalmologicai diagnoses, figures for diastolic and systolic blood pressure, and glycated haemoglobin (HbA1c) levels. The independent variables studied were the CDR, IOP level and the campimeter result. • STATISTICAL ANALYSIS: An analysis was made of the frequencies, and a calculation of the mean, median, standard deviation, minimum and maximum value, and a range for the qualitative variables. The accuracy and behaviour of the retinographies for sensibility (SE), specificity (SP), predictive values (PV) and probability coefficient (PC) were also calculated. There was concordance for the primary open-angle glaucoma (POAG) diagnosis qualitative variable according to the Kappa index, and for the CDR variable by the intraclass correlation coefficient (ICC). A comparison of the means of the quantitative variables was made using the t~Student test, and the qualitative variables were measured by chi-squared testing. The test application conditions were verified taking into account the n of the samples analysed, Q-Q graphics and the Shapiro-Wiik test. A multivariate analysis was performed by binary logistical regression, taking the glaucoma diagnosis as the dependent variable and the rest as independent variables. • RESULTS. POAG prevalence was 8.76% (1C 5.36-13.39). Comparing the analyses of the ophthalmologist to the primary health care doctors, there was a sensibility of 21% (IC 0-43%), a specificity of 93% (IC 89-97%), a PV+ of 20% (IC 0-40%) and a PV- of 94% (IC 90-97%). The PC+ was 3.1 (IC 0.9-9.6) and the CP- was 0.8 (IC 0.6-1.1). The Kappa index was 0.1, and the ICC was 0.7. The results were similar in all the pairs compared. There was a significant statistical difference in the relation between gender and glaucoma diagnosis (p=0.011), it being more frequent among women. A relation was found between the CDR and the POAG diagnosis, with p < 0.001. There was no statistically significant relation between the level of IOP measured in mmHg and the glaucoma diagnosis (p=0.95). In the multivariate analysis, the variables related to the glaucoma diagnosis were cup-to-disc ration (p<0.001, IC 0-0.046) and the campimeter (p=0.015, IC 0.001-0.424). • CONCLUSIONS: Retinography as a tool for filtering glaucoma proved to be insufficiently valid, presenting low sensitivity and high specificity. Concordance as measured by the Kappa index was poor-to-weak. Concordance for the CDR was moderate-to-substantial as measured by the ICC.