TNF-alpha levels in tears: a novel biomarker to assess the degree of diabetic retinopathy.

ABSTRACT

We assess the level of tumour necrosis factor alpha (TNF-alpha) in tear fluids and other serum parameters associated with diabetes in different degrees of diabetic retinopathy. We have performed a prospective, nonrandomized, observational study. Study population consisted of 16 healthy subjects (controls) and 32 type 2 diabetic patients 16 affected by proliferative diabetic retinopathy (PDR) and 16 with nonproliferative retinopathy (NDPR, background/preproliferative). Body mass index, urinary albumin, blood glucose, HbA1c, and tear levels of TNF-alpha were measured in all subjects. The value of glycaemia, microalbuminurea, and Body mass index in diabetic retinopathy groups were higher than those in control group (P < 0.05). Glycemia in NPDR 6.6 mmol/L (range 5.8-6.3); in PDR 6.7 mmol/L (range 6.1-7.2); in control 5.7 mmol/L (range 4.9-6.1); microalbuminurea in NPDR 10.6 mg/L (range 5.6-20); in PDR 25.2 mg/L (range 17-40); in control 5.3 mg/L (range 2.6-10); Body mass index in NPDR 26 Kg/m(2) (range 20.3-40); in PDR 28 Kg/m(2) (range 20.3-52); in control 21 Kg/m(2) (range 19-26). The TNF-alpha concentrations in tears increase with the severity of pathology and were lower in control group than in diabetic subjects. In the end, the level of TNF-alpha is highly correlated with severity of diabetic retinopathy and with nephropathy. Tear fluid collection may be a useful noninvasive method for the detection of proliferative diabetic retinopathy.