Urinary retinol binding protein in Indo‐Asian patients with idiopathic interstitial nephritis

• Published in: QJM : An International Journal of Medicine 2003-05, Vol.96 (5), p.363-367
• Main Authors: Ball, S.T., Lapsley, M., Norden, A.G.W., Cairns, T.D.H., Palmer, A.B.D., Taube, D.H.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Albuminuria - etiology; Asia, Western - ethnology; Biological and medical sciences; Biomarkers - urine; Case-Control Studies; Female; Humans; Interstitial nephritis; Kidney Failure, Chronic - etiology; Male; Medical sciences; Middle Aged; Nephritis, Interstitial - ethnology; Nephritis, Interstitial - urine; Nephrology. Urinary tract diseases; Nephropathies. Renovascular diseases. Renal failure; Pilot Projects; Retinol-Binding Proteins - urine; United Kingdom - epidemiology
• ISSN: 1460-2725; 1460-2393; 1460-2393
• DOI: 10.1093/qjmed/hcg052

Background: Idiopathic interstitial nephritis (IIN) is common in the UK Indo‐Asian population. Lack of systemic involvement and unremarkable urinalysis on stick testing suggest that it may underlie some cases of end‐stage renal failure of undetermined cause. If IIN is diagnosed early, prompt initiation of treatment can improve long‐term outcome. Aims: To investigate whether urinary retinol binding protein (RBP) is elevated more commonly than urinary albumin in IIN, and might be useful in the early detection of renal disease in Indo‐Asian patients. Design: Preliminary observational study Methods:  We measured urinary RBP and urinary albumin in 19 Indo‐Asian patients in whom a renal biopsy had shown IIN, 10 of whom had already been treated with corticosteroids at the time of specimen collection. A further 28 Indo‐Asian patients with glomerular disease, and six with normal light‐microscopic renal biopsy, were assessed in parallel. Results: Urinary RBP/creatinine ratio (RCR) was elevated in all 19 cases of IIN, compared to 12/19 in whom the albumin/creatinine ratio (ACR) was elevated. Elevated urinary RBP was thus significantly more common than albuminuria in this group (p30 times the upper limit of normal in 7/9 who had not previously received corticosteroids, of whom four had normal ACR; none had ACR >5 times the upper limit of normal. Discussion:  These data suggest that measurement of urinary RBP should be explored as an adjunct to albuminuria, if screening for renal disease in the Indo‐Asian population is contemplated.