Novel urinary biomarkers and their association with urinary heavy metals in chronic kidney disease of unknown aetiology in Sri Lanka: a pilot study

Abstract

INTRODUCTION: Chronic kidney disease of unknown etiology (CKDu) has emerged as a significant public health problem in Sri Lanka. The role of environmental exposure to cadmium and arsenic in the aetiology of CKDu is still unclear. Identification of a panel of novel urinary biomarkers would be invaluable in the study of toxin mediated damage postulated to be the aetiology of CKDu. OBJECTIVES: The aims of this study were to evaluate the profile of novel urinary biomarkers in CKDu patients and identify any association with environmental exposure to heavy metals. METHODS: Thirty seven randomly selected CKDu patients attending a renal clinic in the North Central Province and two control groups namely a farmer group (n=39) and a non-farmer group (n=40) from a non-endemic area were included in this comparative cross sectional study. Urine samples were analyzed for heavy metals and five urinary biomarkers. RESULTS: CKDu patients had significantly elevated urinary levels of fibrinogen (198.2 ng/mg creatinine p<0.001), clusterin (3479 ng/mg creatinine p<0.001), cystatin-C (5124.8 ng/mg creatinine p<0.001) and β2-microglobulin (9913.4 ng/mg creatinine p<0.001) compared to the control groups. Fibrinogen and β2-microglobulin were the best to discriminate CKDu patients from normal individuals with the receiver operator areas under the curve being 0.867 and 0.853, respectively. Urinary fibrinogen and KIM-1 levels correlated positively with urinary arsenic levels. KIM-1 levels correlated positively with urinary mercury and lead levels but no correlation was seen with urinary cadmium levels. CONCLUSIONS: Fibrinogen and β2-microglobulin have the potential of being a screening tool for detection of CKDu and may aid the early diagnosis of toxin mediated tubular injury in CKDu. Their usefulness need to be further validated in a larger epidemiological study of patients with early stages.