Association Between Serum Cystatin C and Creatinine in Chronic Kidney Disease Subjects Attending a Tertiary Health Care Centre.

INTRODUCTION: Chronic Kidney Disease (CKD) is an emerging health problem due to the increasing prevalence of conditions like diabetes mellitus and hypertension. Most patients are diagnosed during the later stages of CKD when the clinical symptoms become apparent. There is a need for early diagnosis to prevent disease progression and associated morbidities. Serum Creatinine (SCr) is commonly used among clinicians to determine renal function. However, SCr is affected by several factors and cannot be entirely relied upon. In pursuit of an alternative indicator of renal function, several biomarkers have been discovered and their utility in prompt diagnosis has been evaluated. Among such biomarkers, serum cystatin C (SCysC) has been extensively studied.

AIM: To determine and compare the levels of SCr and SCysC in CKD subjects across various severity groups based on estimated Glomerular Filtration Rate (eGFR).

MATERIALS AND METHODS: The study comprised of 120 CKD subjects. SCr was estimated by modified Jaffe's method and SCysC was estimated by particle enhanced immunoturbidimetric method. Estimated GFR (eGFR) was determined using Chronic Kidney Disease Epidemiology collaboration (CKD EPI) 2009 creatinine based formula. Based on eGFR, CKD subjects were further categorized into four groups. Statistical analysis was done using SPSS. Data were represented as median and interquartile range. Kruskal Wallis test was used for comparison between more than two groups. Correlation was done using Pearson's test. Statistical significance was considered as p <0.05.

RESULTS: Both SCr and SCysC levels increased significantly across CKD groups (p<0.001). In CKD subjects with eGFR ≥ 60 ml/min/1.732 m2 , the median value of SCr (1.01 mg/dl) was well within the normal range while median value of SCysC (1.34 mg/l) was found to be more than the upper reference limit. A positive correlation was present between SCysC and SCr (r=0.875, p<0.001). Both SCysC (r=-0.736) and SCr (r=-0.719) had a negative correlation with eGFR (p<0.001).

CONCLUSION: SCysC is useful in detecting individuals with CKD having mild decrease in GFR compared to SCr. Both SCr and SCysC levels increase with decrease in eGFR. SCysC may be used to screen patients with poorly controlled diabetes mellitus or hypertension when SCr level is inconclusive.