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Comparison of Serum Cystatin C and Creatinine Levels among Individuals with Persisting Proteinuria in Farming Communities of Rural Sri Lanka
Jayasekara, Jayasekara Mudiyanselage Kithsiri Bandara; Dissanayake, Dhammika Maneke; Shihana, Fathima; Sivakanesan, Ramaiya; Silva, Rajith Niloshan & Gunawickrama, Suwanda Hennadige Nandana Priyankara
Abstract
Background: Chronic kidney disease of uncertain aetiology (CKDu) is one of the major
health concerns among agricultural communities in Sri Lanka. Individuals involved in severe
agricultural works for their livelihood are highly vulnerable for this disease and patients have been
detected with persisting proteinuria at community-level screening. The current study was designed
to evaluate the diagnosis of two functional markers of kidney damage using individuals with
persisting proteinuria as the baseline.
Methods: One hundred and fifty hard-working agricultural farmers from high-prevalence
area for CKDu (Madawachchiya) were screened three times for proteinuria; 66 proteinuric
and 21 non-proteinuric were identified as the baseline classification. Selected individuals were
analysed further for creatinine, protein and cystatin C in urine and creatinine, cystatin C in serum.
Urine protein-to-creatinine ratio (UP/UC) was calculated.
Results: Based on creatinine and cystatin C cut-off levels in serum, individuals were
classified as high or normal. Diagnosis of two functional markers (creatinine and cystatin C)
were evaluated using receiver operating characteristic (ROC) curve and in terms of sensitivity
and specificity using UP/UC as the baseline. Creatinine and cystatin C-based eGFR (estimated
Glomerular filtration rate) levels were calculated, and Pearson's correlation coefficient was
determined between different eGFR measurements using UP/UC.
Mean (SD) UP/UC ratio, serum creatinine, and serum cystatin C levels of the proteinuric
subjects were 129.0 (18.4) mg/mmol, 1.35 (0.39) mg/dL, 1.69 (0.58) mg/L. For non-proteniuric
individuals, the results were found to be 14.4 (2.28), 1.22 (0.40) mg/dL, 0.82 (0.25) mg/L.
The ROC analysis showed excellent accuracy in using cystatin C for identifying proteinuric patients
than creatinine area under the curve (AUC): 0.9675, P < 0.001). Cut-off points were identified as
1.015 mg/dL for serum creatinine and 0.930mg/L for cystatin C. Furthermore, cystatin C based
Hoek formula showed the better correlation (0.635, P < 0.001) with UP/UC compared with
creatinine based modification of diet in renal disease (MDRD) formula.
Conclusion: The study showed elevated serum cystatin C in patients with persisting
proteinuria compared with non-responding serum creatinine. Moreover, cystatin C-based
eGFR equations were more accurate to determine the kidney function than serum creatinine in
proteinuric patients who are vulnerable for CKDu in high-prevalence areas.
Keywords
persistent proteinuria; cystatin C; chronic kidney disease of uncertain aetiology; Sri Lanka
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