Clinical prediction score for diagnosing non-diabetic renal disease in patients with type 2 diabetes mellitus: a cohort study

Background: When non-diabetic renal disease (NDRD) is suspected, kidney biopsy is used for definite diagnosis; however, this is not always easily available and may lead to complications. A clinical prediction score may help selecting appropriate patients for kidney biopsy.Methods: A retrospective cohort study was conducted in type 2 diabetes mellitus (T2DM) patients with atypical features of diabetic nephropathy (DN), who had kidney biopsy at Thammasat University Hospital from 2011-2019. We divided patients into NDRD alone, coexisting NDRD and DN, and DN alone, confirmed by pathological diagnosis. We developed a clinical prediction score by weighing coefficients of predictors in a multivariable logistic model. Internal validation was performed with bootstrapping.Results: We included 81 patients: 28 (34%) had NDRD alone, 15 (18%) had coexisting NDRD and DN, and 38 (41%) had DN alone. Primary membranous nephropathy, primary focal and segmental glomerulosclerosis (FSGS), and secondary FSGS were prevalent in any NDRD. Absence of diabetic retinopathy (DR) showed a significant association with any NDRD (OR 3.72; 95% CI, 1.28-10.8; p=0.02). The prediction score, AUC of 0.75 (95% CI, 0.63-0.86), had four predictors: duration of DM <10 years, eGFR >30 ml/min/1.73m2, HbA1c <8%, and absence of DR. Higher scores were associated with higher probability of NDRD.Conclusions: This clinical prediction score appears to be a useful tool to determine NDRD probability. T2DM patients with atypical presentation of DN with lower scores (0-2) may defer kidney biopsy.