Is serum cystatin C an accurate endogenous marker of glomerular filteration rate for detection of early renal impairment in patients with type 2 diabetes mellitus?
BACKGROUND
Researches have recently reported that serum cystatin C is a more sensitive marker of changes in glomerular filtration rate (GFR) than serum creatinine. We conducted this study to evaluate the significance of serum cystatin C as a more sensitive marker of GFR for early detection of renal impairment in special groups of patients with type 2 diabetes mellitus (DM).


METHODS
The present study included 40 patients with type 2 DM divided into four equal groups based on their urinary albumin excretion and renal function: group 1 was normoalbuminuric, group 2 was microalbuminuric, group 3 was macroalbuminuric, and group 4 was macroalbuminuric with renal dysfunction. All patients underwent a thorough history, full clinical examination, fasting, and renal function tests. Post-prandial blood glucose levels, glycosylated hemoglobin A1c (HbA1c), proteins, albumin in 24 hr urine, and serum cystatin C were collected.


RESULTS
Serum cystatin C and creatinine were significantly higher in macrolbuminuric type 2 diabetic patients with renal dysfunction (group 4: 2.26 +/- 1.28, 4.21 +/- 2.38 mg/dl, respectively; p < 0.001) than macrolbuminuric type 2 diabetic patients with normal renal function (group 3: 1.04 +/- 0.24, 0.96 +/- 0.20 mg/dl, respectively), the microalbuminuric group (0.87 +/- 0.28, 0.71 +/- 0.12 mg/dl, respectively), as well as the normoalbuminuric group (0.55 +/- 0.41, 0.60 +/- 0.18 mg/dl, respectively). ROC plots demonstrated that area under the curve (AUC) of cystatin C (0.74) was greater than that for creatinine clearance (cr.cl) (0.67) and serum creatinine (s-cr) (0.74); therefore, the sensitivity and diagnostic accuracy of cystatin c was better than cr. cl., and both were better than s-cr. Serum cystatin C showed significant correlation in groups 2-4 with s-cr, cr.cl, and 24 hr urine albumin, but no correlation was found in group 1.


CONCLUSIONS
Serum cystatin C is a reliable and easily performed marker for GFR to detect renal impairment in patients with type 2 DM.
El-Shafey
E M
EM
Internal Medicine, Nephrology Department, Faculty of Medicine, Tanta University, Tanta, Egypt. shafey70@yahoo.com
El-Nagar
G F
GF
Selim
M F
MF
El-Sorogy
H A
HA
Sabry
A A
AA
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D055316:Cystatin C / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D003928:Diabetic Nephropathies / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D018450:Disease Progression; D042241:Early Diagnosis; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D015994:Incidence; D008297:Male; D011237:Predictive Value of Tests; D011336:Probability; D011379:Prognosis; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D017678:Sex Distribution
D015415:Biomarkers; D055316:Cystatin C