Predictability of Nailfold Capillaroscopic Score in Diagnosing Retinopathy in Patients with Type 2 Diabetes Mellitus and its Utility as a Non-Invasive Tool for Differentiating from those Not Having Retinopathy

Diabetes mellitus (DM) is a chronic hyperglycaemic state associated with microvascular structural alterations. Nailfold capillaroscopy (NFC) is an in vivo study of microvascular circulation.This study aimed to investigate the diameters of capillary loops and morpho-structural changes using a handheld dermatoscope in patients with type 2 DM (T2DM) with and without diabetic retinopathy (DR) and to establish nailfold capillary changes and NFC score as a non-invasive method to identify microvascular complication in T2DM patients.A cross-sectional observational study was conducted in AIIMS Rishikesh for 6 months from August 2022 to February 2023. Our study participants were 100 adults more than 18 years of age diagnosed with T2DM, based on the American Diabetes Association (ADA) criteria. All patients were evaluated thoroughly for the presence of microvascular complications in the form of retinopathy. Based on this, they were divided into two groups-group 1 (T2DM with retinopathy) and group 2 (T2DM without retinopathy). Both groups were further subdivided into three subgroups based on haemoglobin A1c (HbA1c): the first group with HbA1c <7%, the second group with HbA1c 7-8.9% and the third group with HbA1c >=9%. For all the study participants, a detailed NFC was done for all 8 fingernails (excluding the thumb), using a handheld dermatoscope. Abnormal capillary shapes (ACS) were recorded by semi-quantitative score (NFC score).A significant association was seen in capillary density (loops/mm) (5.83 ± 0.72 in the DR group and 6.3 ± 0.89 in the no-DR group) (P value = 0.005), capillary density (loops/3 mm) (P value = 0.005), total number of microhaemorrhages/3 mm (P value < .0001), total number of giant capillaries/3 mm (P value = 0.0004), total number of avascular areas/3 mm (P value = 0.0005), enlarged capillaries/3 mm (P value = 0.002), tortuous capillaries/3 mm (P value < .0001), abrogated/bushy capillaries/3 mm (P value = 0.004), number of fingers involved excluding the thumb (P value < .0001) and total nailfold capillaroscopic score (P value < .0001) between the two groups, one with DR and another without DR. Furthermore, the proportion of patients with abnormal nailfold capillaroscopic findings, abnormal NFC score, was significantly higher in patients with DR as compared to patients without DR (51.85% vs 4.35%, respectively) (P value < 0.0001).Our results suggest that NFC could possibly be used as an adjunctive tool in diabetics for diagnosing or monitoring microvascular complications with total NFC score being the significant predictor of DR at a cut-off point of >0 with the area under the curve (AUC) of 0.745 for correctly predicting DR.