Assessment of red blood cell distribution width(RDW) as a biomarker of diabetic nephropathy in type II Diabetes Mellitus patients reviewed at Kabwe General Hospital
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Background: Diabetic nephropathy (DN) is a kidney disease that is a complication of diabetes. Pathogenesis of DN involves damage to the tiniest blood vessels which is followed by increased concentration of blood urea / creatinine and urine albumin excretion. DN is the leading cause of morbidity and mortality in patients with diabetes mellitus. Multiple factors and mechanisms such as interaction between hyperglycemia-induced metabolic and hemodynamic changes and genetic predisposition have been attributed to the development and outcomes of diabetic nephropathy. Diagnosis of DN in Zambia has been limited to the detection of elevated levels of creatinine, urea and urine albumin in the blood and urine respectively. We set out a comparative study to assess red blood cell distribution width (RDW) as a diagnostic marker of diabetic nephropathy in type 2diabetes mellitus patients. Methods: A Structured questionnaire was used to capture age, sex, history of blood transfusion and cancer status of the participants. Urea, creatinine and urine albumin concentrations were measured and RDW determined in 122 type 2 diabetes mellitus patients and 61 non diabetic participants. Renal profile tests (creatinine, urea and urine albumin) were used as a proxy marker for diabetic nephropathy in type 2 diabetes mellitus patients. Patients with high renal profile tests (urea > 8.3 mmol/l, creatinine > 120µmol/l, urine albumin > 30mg/l) were considered to have diabetic nephropathy. This study was approved by the University of Zambia Biomedical Research Ethics Committee (Assurance No.FWA00000338, IRB00001131 of IOR0000774) and the ministry of health in Zambia. Results: The results revealed that mean creatinine concentration for type 2 diabetes mellitus patients (750 + 4.0 µmol/l ) was significantly higher than control participants (250 + 2.1 µmol/l ) t – value 5.00; P – value = 0.003. The mean urea concentration for type 2 diabetes mellitus patients (4.2 + 2.4 mmol/l) was significantly higher than control participants (2.2 + 1.5 mmol/l). t – Value = 8.26; p – value 0.002.The mean urine albumin concentration for type 2 diabetes mellitus patients (12.4 + 3.3 mg/l) was higher than the control participants (12.2 + 2.9 mg/l) but the difference was not significant t – value 5.41; p – value 0.168. The mean RDW for type 2 diabetes mellitus patients (32.2 + 4.2 %) was significantly higher than the control participants (14.7 + 3.8 %). t – value 7.58; p – value 0.001.The diagnostic performance of RDW and renal profile tests (urea, creatinine and urine albumin; standard proxy) were compared based on sensitivity, specificity, positive predictive value (PPV), negative predictive (NPV) and test efficiency.RDW was found to have sensitivity of 93%, specificity of 96%, PPV 97%, NPV 91% and efficiency of 94% which were very significant parameters to warrant the inclusion of RDW as one of the diagnostic markers of diabetic nephropathy. Conclusion: Using diagnostic sensitivity, specificity, PPV, NPV and efficiency, it was found that RDW was a reliable and suitable biomarker for detecting diabetic nephropathy in type 2 diabetes mellitus patients.