CORRELATION STUDY OF SERUM CYSTATIN C AND CREATININE FOR EARLY DETECTION OF CHRONIC KIDNEY DISEASE AMONG PATIENTS AT RISK IN BENIN, NIGERIA

Abstract

Background: Glomerular filtration rate (GFR) is important for assessing the functional
capacity of the kidney. Reduction in GFR ≤ 60ml/min/1.73m2 or presence of kidney
damage defines Chronic Kidney Disease (CKD). Progression of kidney disease without
medical intervention is associated with increase morbidity and mortality. Risk factors like
uncontrolled diabetes mellitus, hypertension and obesity have been shown to be
associated with CKD. These factors act synergistically to cause progressive decline in
GFR and renal function. Traditionally, GFR is estimated based on serum Creatinine
concentration using Creatinine based formula such as Cockroft-Gault but this is not
sensitive for early prediction of CKD. However, there are reports that serum Cystatin C
concentration is a better indicator of GFR especially in those patients at risk of
developing chronic kidney disease.
Aim and Objectives: This study examined the correlation between Creatinine and
Cystatin C based estimations of glomerular filtration rate (GFR) among patients at risk
of developing CKD.
Methodology: Serum samples were assayed for estimation of Creatinine and Cystatin
C in 172 subjects divided into four subgroups and 64 subjects serving as controls. Two
results for estimated glomerular filtration rate (eGFR) were generated using serum
creatinine (Cr) and cystatin C. Cockroft-Gault formula was used to calculate eGFR-Cr
and simple cystatin C formula was used to calculate eGFR-Cystatin. The results of
eGFR were correlated and compared between the subjects and controls. Receiver

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operator curves were constructed and analysed to determine the diagnostic accuracy
between simple Cystatin C formula and Cockroft-Gault formula.
Results: There was a significant (p < 0.001) reduction in eGFR-cystatin compared to
eGFR-Cr in the subjects (64.6.0±46.7ml/min/1.73m2 vs 93.6.0±36.9ml/min/1.73m2).
Estimated GFR based on Creatinine and Cystatin C were lower in the subjects than the
controls (93.6±36.9ml/min/1.73m2 vs 64.6±46.7ml/min/1.73m2 and
103.7±29.7ml/min/1.73m2; 112.5±46.4ml/min/1.73m2) respectively.
Cystatin C based estimated GFR (eGFR-Cystatin) was significantly (p< 0.05) lower than
eGFR-Cr among the diabetics (53.9±37.4m/min/1.73m2 vs 80.3±22.5ml/min/1.73m2);
hypertensives/diabetics (49.5±43.5ml/min/1.73m2 vs 87.9±33.3ml/min/1.73m2) and
obesed (84.4±48.2ml/min/1.73m2 vs 115.3±49.3ml/min/1.73m2) subjects.
Subjects with both hypertension and diabetes mellitus had the worst eGFR-cystatin.
Receiver operator curves (ROC) show a higher area under the curve for Cystatin C
based GFR as against creatinine based GFR although the two AUCs are comparable
(0.807 vs 0.673). Diabetic patients especially those with comorbidity had the worst
eGFR among the subgroups.
Conclusion: Serum Cystatin C appears to be more predictive of mild reduction in
glomerular filtration rate than creatinine especially in those patients with identified risk
factors for chronic kidney disease who are asymptomatic.