Microalbuminuria better predictor for retinopathy than eGFR in diabetes
MedWire News: Microalbuminuria is a more useful biomarker than moderately decreased estimated glomerular filtration rate (eGFR) for predicting retinal outcome among Type 2 diabetes patients, report researchers.
Patients with microalbuminuria (urinary-to-creatinine ratio [UACR] 30.0-299.9 mg/g creatinine) have a higher risk for the development and progression of diabetic retinopathy (DR) even when eGFR is adequate (>60 mL/min per1.73 m2), say Harn-Shen Chen (National Yang-Ming University, Taipei, Taiwan) and colleagues.
The researchers explain that although the prevalence and risk factors for DR in Type 2 diabetes have been extensively investigated, there are little data addressing the issue of whether microalbuminuria or moderate impairment of eGFR (30-59.9 mL/min per 1.73 m2) is a competing risk factor for the development and progression of DR.
To investigate, Chen and team recruited 777 Type 2 diabetes patients (aged 18 years or older) who were receiving regular follow-up at outpatient clinics between August 2001 and December 2002.
All participants underwent baseline examination of eye fundus photographs and assessment of serum creatinine, urine albumin excretion, and glycemic and lipid parameters.
The team assessed the patients using the Early Treatment Diabetic Retinopathy Study (ETDRS) severity scale and excluded those with advanced diabetic retinopathy (defined as the development of proliferative DR or retinopathy treated with laser photocoagulation or vitrectomy). Those with missing eGFR and UACR data, and those with an eGFR of less than 30 mL/min per 1.73 m2 and/or a UACR of more than 300 mg/g creatinine were also excluded, to give a final study population comprising 487 individuals.
As reported in Diabetes Care, 81 patients had normoalbuminuria (UACR <30 mg/g creatinine) and moderate renal impairment and 106 had microalbuminuria without moderate renal impairment at baseline.
The researchers followed-up the patients for a median of 7.6 years. The primary endpoints were the development and progression of DR (an increase of at least three steps on the ETDRS severity scale or development of advanced DR), and progressive loss of renal function, defined as an eGFR decrease of 15 mL/min per 1.73 m2 and final eGFR of less than 60 mL/min per 1.73 m2.
The study revealed that patients with microalbuminuria who did not have moderate renal impairment were at a significantly greater risk for the development and progression of DR compared with those with normoalbuminuria who did have moderate renal impairment, at an adjusted hazard ratio of 3.34.
There were no significant differences in risk for renal outcome, cardiovascular events, and all-cause mortality between the groups, report the researchers.
"We emphasize the importance of regular follow-up of UACR beside eGFR in Type 2 diabetes patients, and changes in UACR and eGFR should also be identified during follow-up," write Chen et al.
Once microalbuminuria occurs, diabetic retinopathy should be more aggressively assessed in these patients even if eGFR is 60 mL/min per 1.73 m2 or more, they conclude.
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By Sally Robertson