title: Correlation of biomarkers thiobarbituric acid reactive substance, nitric oxide and central subfield and cube average thickness in diabetic retinopathy: a cross-sectional study.
abstract: BACKGROUND
  To evaluate the role of thiobarbituric acid reactive substance (TBARS) and nitric oxide (NO) as biochemical biomarkers and central subfield (CST) and cube average thickness (CAT) as biomarkers for medical imaging in diabetic retinopathy.
  
  
  METHODS
  Forty consecutive cases of diabetic retinopathy and 20 healthy controls were included. Cases were divided into two groups: non proliferative diabetic retinopathy (n = 20) and proliferative diabetic retinopathy (n = 20) according to ETDRS classification. LogMAR visual acuity was documented. Plasma levels of TBARS, NO and glycated hemoglobin (HbA1c) were measured using standard protocol. CST and CAT were analyzed on spectral domain optical coherence tomography. Data was analyzed statistically.
  
  
  RESULTS
  Increased severity of diabetic retinopathy was associated with an increase in plasma levels of TBARS (F = 10.92; p < 0.001), NO (F = 21.8; p < 0.001) and HbA1c (F = 5.87; p = 0.001). Increase in CST (F = 61.51; p < 0.001) and CAT (F = 60.84; p < 0.001) was also found to be associated with increased severity of diabetic retinopathy. Pearson's correlation analysis revealed a positive correlation of TBARS with CST (r = 0.29; p = 0.038) and CAT (r = 0.31; p = 0.04). A positive correlation of NO with CST (r = 0.27; p = 0.03) and CAT (r = 0.7; p = 0.001) was also observed. On univariate analysis with logMAR visual acuity as dependent variable, a significant increase in visual acuity was observed with increase in independent variables TBARS (B = 0.22; p = 0.004), NO (B = 0.006; p < 0.001), CST (B = 0.005; p < 0.001) and CAT (B = 0.005; p < 0.001). On multivariate linear regression analysis with logMAR visual acuity as dependent variable and adjusting for other factors like duration of diabetes and HbA1c, it was observed that increase in independent variables TBARS (B = 0.07), NO (B = 0.001) and CST (B = 0.004) independently predict increase in logMAR visual acuity (p < 0.001).
  
  
  CONCLUSIONS
  Thiobarbituric acid reactive substance and nitric oxide serve as potential biochemical markers whereas central subfield and cube average thickness serve as potential biomarkers for medical imaging for severity of diabetic retinopathy. In a clinical retinal setting, CAT and CST will help in early recognition of increase in severity of diabetic retinopathy.
authors.affiliation: Department of Ophthalmology, King George's Medical University, Lucknow, India.
authors.forename: Surabhi
authors.initials: S
authors.lastname: Ruia
authors.affiliation: Department of Ophthalmology, King George's Medical University, Lucknow, India.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Saxena
authors.affiliation: Department of Community Medicine, King George's Medical University, Lucknow, India.
authors.forename: S
authors.initials: S
authors.lastname: Prasad
authors.affiliation: Department of Ophthalmology, King George's Medical University, Lucknow, India.
authors.forename: Shashi R
authors.initials: SR
authors.lastname: Sharma
authors.affiliation: Department of Ophthalmology, Saint Louis University Eye Institute, Saint Louis University, Saint Louis, MO USA.
authors.forename: Levent
authors.initials: L
authors.lastname: Akduman
authors.affiliation: Developmental Toxicology Division, Indian Institute of Toxicology Research, Lucknow, India.
authors.forename: Vinay K
authors.initials: VK
authors.lastname: Khanna
keywords: Central subfield thickness; Cube average thickness; Diabetic retinopathy; Nitric oxide; Oxidative stress; Spectral domain optical coherence tomography; Thiobarbituric acid reactive substance