Comparison of renal function markers in Kuwaiti patients with sickle cell disease.
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, beta(2)-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, beta(2)-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, beta(2)-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.
Department of Pathology, Faculty of Medicine, Kuwait University, Kuwait.
R
R
Marouf
O
O
Mojiminiyi
N
N
Abdella
M
M
Kortom
H
H
Al Wazzan
D000328:Adult; D000755:Anemia, Sickle Cell / Q000097:blood* / Q000652:urine; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood / Q000652:urine; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007730:Kuwait; D008297:Male; D008875:Middle Aged; D011507:Proteinuria / Q000175:diagnosis; D012680:Sensitivity and Specificity; D001613:beta 2-Microglobulin / Q000097:blood*
D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D006454:Hemoglobins; D001613:beta 2-Microglobulin; D003404:Creatinine