Validity of Serum Cystatin C as an Early and Accurate Marker of Glomerular Filtration Rate in type 1 Diabetes Mellitus Patients

The present study aims at exploring the clinical validity of measuring cystatin C for the early and accurate assessment of GFR (as compared to measuring serum creatinine or β2 microglobulin) in patients suffering from type 1 diabetes mellitus who are at risk of developing diabetic nephropathy as well as those who have already developed the condition. This study included 80 subjects who were further subdivided into two groups: Control group (1) which comprised 20 healthy age and sex matched children. Patient group (2) comprised 60 patients of both sexes properly diagnosed with type 1 diabetes. The patients were further subdivided into 3 subgroups according albumin levels in their 24 hour urine : Group 2a: 20 patients who were considered normo-albumin uric. Group 2b: 20 patients who were considered micro-albumin uric. Group 2c: 20 patients who were considered macro - albumin uric. All subjects were subjected to the estimation of serum creatinine level as well as serum β2 microglobulin and serum cystatin C levels. They were also subjected to Isotope renogram using ^99mTc- diethylene triamine pentaacetic acid (DTPA) single injection technique for accurate measurement of glomerular filtration rate (GFR). A positive correlation was observed between each of serum creatinine, β2 microglobulin, cystatin C with albumin in 24 hr urine in all the patient subgroups and this correlation was highly significant. However, the correlation between serum cystatin C levels in the diabetic patients and albumin in 24 hr urine was higher than that observed for either serum creatinine or serum β2 microglobulin. Cystatin C had the highest negative correlation with GFR (as measured by ^99mTc-DTPA clearance) compared to either serum creatinine or serum β 2 microglobulin in group II patients. It can be concluded that cystatin C could act as an early and accurate marker of GFR and renal function in patients with type 1 diabetes mellitus at risk of developing or who have already developed diabetic nephropathy deficiencies