HIDDEN RENAL DISFUNCTION IN TYPE 2 DIABETES MELLITUS: DIAGNOSTIC UTILITY OF SERUM CYSTATIN C IN NORMOALBUMINURIC AND MICROALBUMINURIC PATIENTS FROM MYSORE DISTRICT, KARNATAKA – AN OBSERVATIONAL STUDY

Abstract

Diabetic nephropathy (DN) is among the most serious microvascular difficulties of Diabetes Mellitus and a leading reason for chronic kidney disease worldwide, is conventionally identified using microalbuminuria; however, renal dysfunction often begins prior to the appearance of overt albuminuria, resulting in delayed diagnosis and intervention. Early detection of subclinical renal impairment is therefore critical, particularly in high-risk South Asian populations with rapidly increasing diabetes prevalence. Serum cystatin C, a low–molecular-weight protein freely filtered by the glomerulus, has emerged as a promising biomarker capable of detecting early decline in renal function before conventional indicators become abnormal. The present cross-sectional study represents one of the first regional epidemiological validations from Mysuru, Karnataka, evaluating the analytical usefulness of serum cystatin C for timely detection of diabetic nephropathy in patients with Type 2 Diabetes Mellitus (T2DM). A total of 200 T2DM patients aged 35–70 years were enrolled and categorized into normoalbuminuric (ACR <30 mg/g; n=100) and microalbuminuric groups (ACR 30–300 mg/g; n=100). Serum cystatin C, creatinine, fasting blood glucose, and HbA1c levels were measured, while glomerular filtration rate (eGFR) was estimated using the CKD-EPI equation. Statistical significance was considered at p < 0.05. The higher correlation value of 0.89 suggests that serum cystatin C have a better and accurate diagnostic potential for identifying early renal impairment. Meanwhile serum creatinine and eGFR exhibited comparatively lower accuracies with AUC values of 0.72 and 0.75, respectively. Moreover, cystatin C showed better sensitivity among multiple specificity limits and maintained higher performance at lower false-positive rates, allowing effective identification of early renal dysfunction even among normoalbuminuric diabetic patients without noticeable clinical indication of nephropathy. In conclusion, the study reports significant regional epidemiological evidence from Mysuru, Karnataka, supporting cystatin C in serum as a sensitive and dependable biomarker for a timely detection of subclinical diabetic nephropathy.