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Comparison of renal function markers in Kuwaiti patients with sickle cell disease

¹ Department of Pathology, Faculty of Medicine, Kuwait University, Kuwait
² Department of Medicine, Faculty of Medicine, Kuwait University, Kuwait
³ Ministry of Health, Kuwait

Correspondence to:
Dr Rajaa Marouf
Kuwait University, PO Box 24923, Safat, Kuwait 13110; r-marouf{at}hsc.edu.kw Background: Proteinuria is a common manifestation of renal disease which is a significant cause of morbidity in patients with sickle cell disease (SCD).

Objective: To evaluate and compare cystatin C, ß₂-microglobulin, and creatinine as markers of renal disease in relation to the degree of proteinuria and other complications of SCD.

Methods: 24 h urine collections were used for estimation of urine protein and creatinine clearance in 59 patients with SCD. Results were correlated with plasma cystatin C, ß₂-microglobulin, creatinine, glomerular filtration rate (GFR; derived from plasma creatinine by Cockcroft-Gault, MDRD formulae, and calculated cystatin C clearance), and clinical and haematological variables.

Results: Comparing the different methods of GFR, the proportion of patients with hyperfiltration (GFR >140 ml/min) were 30.5% (MDRD), 44.1% (Cockcroft-Gault), and 10.2 % (calculated cystatin C clearance). Cystatin C was the most consistent marker of hyperfiltration. The endogenous markers of GFR showed an increasing trend with increasing proteinuria, but haematological variables were not correlated with cystatin C, ß₂-microglobulin, or plasma creatinine. Urine protein excretion was correlated with age (r = 0.33) and significant proteinuria was present in 13.6% of patients. Patients with proteinuria had lower haemoglobin concentration (p = 0.027) than those without proteinuria but HbF was not related to the degree of proteinuria or to markers of GFR.

Conclusions: Markers of GFR show variable ability to identify hyperfiltration in patients with SCD, but cystatin C is the best endogenous marker. Proteinuria is associated with age, haemoglobin, and abnormalities of GFR. Routine screening is recommended to allow for early detection and intervention.

Abbreviations: GFR, glomerular filtration rate; MDRD, modification of diet in renal disease; SCD, sickle cell disease

Keywords: cystatin C; ß2-microglobulin; glomerular filtration rate; sickle cell disease