Methodological quality of the review: Medium confidence

Author: He F, Xia X, Wu XF, Yu XQ, Huang FX.

Region: Europe, India, Japan, Malaysia, China, Kuwait, Korea Thailand and United States of America (USA).

Sector: Diabetic retinopathy, diabetic nephropathy.

Sub-sector: Type 2 diabetes, renal disease.

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis methods: Not applicable

Background

Approximately 40% of people with diabetes develop diabetic nephropathy (DN), which has become the leading cause of end-stage renal disease in developed countries. Kidney biopsy is an effective method for identifying DN from non-diabetic renal disease (NDRD), although it cannot be performed on all patients due to contraindications. However, the assessment of diabetic retinopathy is a convenient, accessible potential method for predicting DN. Previous studies have shown that diabetic retinopathy may be helpful in distinguishing the type of kidney pathology in patients with type 2 diabetes mellitus and renal disease. However, these studies have been diverse, showing varied results.

Research objectives

To ‘determine the predictive value of diabetic retinopathy in differentiating diabetic nephropathy from non-diabetic renal diseases in patients with type 2 diabetes and renal disease.’

Main findings

The authors identified 26 prospective studies, nine prospective studies and 17 retrospective studies for inclusion in the review that looked at renal diseases based on kidney biopsy findings and/or the presence of DR and numbers of patients classified in each renal disease group. Studies included were conducted in Europe, Asia, North America and the Middle East.

The pooled sensitivity and specificity of DR to predict DN were 0.65 (95% CI 0.62, 0.68) and 0.75 (95% CI 0.73, 0.78) respectively. The pooled positive and negative predictive value of DR to predict DN were 0.72 (95% CI 0.68, 0.75) and 0.69 (95% CI 0.67, 0.72) respectively.

The authors considered that DR had a potential role in predicting or screening for diabetic nephropathy in patients with type 2 diabetes and renal disease. Measuring DR may be useful in predicting DN since it was simplistic and non-invasiveness. Proliferative diabetic retinopathy may be a highly specific indicator for diabetic nephropathy.

Methodology

Authors searched MEDLINE and EMBASE (from inception to 2012) and references from retrieved articles and reviews identified were manually searched for further articles. The inclusion criteria included the identification of renal diseases based on kidney biopsy findings and the presence of DR and numbers of patients classified in each renal disease group.

Data for each study was extracted using standard forms, obtaining information on study design, author, publication year, duration of diabetes and many others. Data was collected at baseline in the case of longitudinal studies. Study quality was assessed using QUADAS quality assessment checklist. The authors conducted meta-analysis of the results of included studies.

Applicability/external validity

The authors did not specifically address the external validity of the review, although they did mention that studies included in the review were of robust and generally high quality.

Geographic focus

The review reported the countries of the included studies but did not specifically focus on low- and middle-income countries or make comment of the review’s applicability to this setting.

Quality assessment

This review was attributed medium confidence in the conclusions about the effects of this study. The literature search, although covering relevant databases and reference lists in included studies, was not sufficiently comprehensive to be confident that relevant studies were not omitted.

Authors conducted a meta-analysis of the data and methods used to pool data were clear. Authors noted that heterogeneity between the studies was high and authors reported the limitations of the review. For example, baseline risk factors were not standardized between the studies and ethnic origin affected the susceptibility of DR development even after adjustment for other risk factors. Hyperglycaemia, hypertension and dyslipidaemia had all been confirmed to have an effect on DR and patient information detailing these risk factors were not available to the authors.