Abstract:
Introduction : Chronic Kidney Disease (CKD) is an increasing cause of
morbidity and mortality worldwide. Chronic Kidney Disease of
Unknown etiology (CKD-u), a tubular interstitial nephropathy,
is an emerging epidemic among farmers in North-Central
region of Sri Lanka.
Serum creatinine remains unchallenged, as the marker of
renal function and most appropriate test for screening. One
major disadvantage of creatinine is that it remains within
normal range even with 50% loss of renal function. Due to
limitations of serum creatinine and other available biomarkers
of CKD ,there is a huge demand for novel validated markers
in screening and clinical care.
Retinol binding protein 4 (RBP4) is a low molecular weight
protein, which is mainly synthesized in the liver belonging to
the lipocalin super family. Its main function is to transport
retinol (vitamin A).
The role of urinary RBP4 as a biomarker of CKD in proximal
tubular diseases, glomerulopathies and in transplantation is
well established. Beyond the typical proximal tubulopathies, it
has been shown that urinary RBP4 is associated with the risk
of CKD progression in some other conditions.
The aim of this study was to determine the level of urinary
RBP4 as a marker of disease severity in CKD-u patients in
Girandurukotte and Wilgamuwa area in Sri Lanka.
Method : Thirty nine biopsy proven CKD-u patients from Girandurukotte
and Wilgamuwa renal clinics were studied.
Blood and random urine samples were collected from
participants and centrifuged for 15 minutes at 4000 rpm.
Centrifuged urine samples were frozen at -80ºC until assay.
RBP4 level was measured in urine by MILLIPLEX MAG
CERTKD panel 05 in a Luminex MAGPIX platform. All
procedures were performed in accordance with the
manufacturer’s instructions.
Separated serum was used to measure serum creatinine and
estimated glomerular filtration rate (eGFR) was calculated.
The disease was categorized into five clinical stages,
according to the Kidney Disease Outcomes Quality Initiative
(KDOQI) criteria based on the eGFR. Data was analyzed
using R programming language.
Results : The median urinary RBP4 levels gradually increased with the
advancing clinical stage of CKD.
There was a negative correlation between the eGFR and the and the
urinary RBP4 level (-0.5362).
Conclusion : Our results suggest that urinary RBP4 could be a marker of
disease severity in CKD-u patients in Sri Lanka. However, a
larger control study would be needed to validate these
findings.
