Detection of diabetic macular oedema: validation of optical coherence tomography using both foveal thickness and intraretinal fluid

Abstract

No studies have yet evaluated jointly central foveal thickness (CFT) and the presence of intraretinal fluid (PIF) to diagnose diabetic macular oedema (DMO) using optic coherence tomography (OCT). We performed a cross-sectional observational study to validate OCT for the diagnosis of DMO using both CFT and PIF assessed by OCT (3D OCT-1 Maestro). A sample of 277 eyes from primary care diabetic patients was assessed in a Spanish region in 2014. Outcome: DMO diagnosed by stereoscopic mydriatic fundoscopy. OCT was used to measure CFT and PIF. A binary logistic regression model was constructed to predict the outcome using CFT and PIF. The area under the ROC curve (AUC) of the model was calculated and non-linear equations used to determine which CFT values had a high probability of the outcome (positive test), distinguishing between the presence or absence of PIF. Calculations were made of the sensitivity, specificity, and the positive (PLR) and negative (NLR) likelihood ratios. The model was validated using bootstrapping methodology. A total of 37 eyes had DMO. AUC: 0.88. Positive test: CFT ≥90 µm plus PIF (≥310 µm if no PIF). Clinical parameters: sensitivity, 0.83; specificity, 0.89; PLR, 7.34; NLR, 0.19. The parameters in the validation were similar. In conclusion, combining PIF and CFT provided a tool to very precisely discriminate the presence of DMO. Similar studies are needed to provide greater scientific evidence for the use of PIF in the diagnosis of DMO.

External validation of cut-off points for foveal thickness taking into account the intraretinal fluid using optical coherence tomography to diagnose diabetic macular oedema

“…The study design was cross-sectional observational with the objective of externally validating the diagnostic test published by Hernández-Martínez et al (2015) in our geographical area. A random sample of diabetic patients who attended hospital ophthalmology services between October 2012 and June 2013 was selected.…”

“…To perform the indicated measurement, an area of 6 mm in diameter was used, where the centre was the fovea, to thus obtain an area of 1,000 central microns for the assessment. To measure the presence of intraretinal fluid (cysts or hyporeflective spaces), the ophthalmologist examined the horizontal OCT image of the retina (B-Scan) ( Azrak et al, 2015a ; Azrak et al, 2015b ; Hernández-Martínez et al, 2015 ).…”

“…Thus, we could have patients without diabetic macular oedema as diagnosed by the Gold standard but in whom an OCT indicates the presence of intraretinal fluid. At the end of 2015, a paper was published that did combine both parameters ( Hernández-Martínez et al, 2015 ). This study determined cut-off points for foveal thickness depending on whether OCT imaging revealed intraretinal fluid.…”

“…This should be analysed in depth before comparing the value 310 µm with the already known value. On the other hand, these cut-off points were internally validated through bootstrapping, obtaining both the area under the Receiver Operating Characteristic curve (AUC) and the calibration (sensitivity and specificity) ( Hernández-Martínez et al, 2015 ). To date, these cut-off points have not been externally validated, that is, in a different sample of patients.…”

“…If satisfactory values are found, we can then say that the test has been validated and may be implemented in clinical practice in our community, as we would have a more exact screening test for diabetic macular oedema. This would result in a reduction in the care load of ophthalmological services since the test could be undertaken by health care personnel not specialised in ophthalmology with a latest generation OCT that focuses on the retina automatically ( Hernández-Martínez et al, 2015 ).…”