Is Screening for Microalbuminuria Warranted in Children with Sickle Cell Hemoglobinopathies?.

Renal impairment occurs in adults and children with sickle cell disease. Microalbuminuria (MA) defined as albumin excretion >2.9 mg/dl in random urine sample or 30–300 mg in 24 hour urine collection is an early, sensitive indicator for glomerulopathy in both diabetes mellitus and sickle cell disease. Therefore, we conducted a universal screening in our patients (pts) with sickle cell hemoglobinopathies in order to identify the prevalence of MA and other indicators of early renal impairment. Children and young adults with hemoglobin SS, SC, Sβ⁺thalassemia and Sβ⁰thalassemia, ages 4–21 years (yrs), had urinalyses and random urine measurements for protein, microalbumin, and creatinine. All were in good state of health, free of pain, and without prior diagnosis of renal dysfunction when the samples were obtained. Serum electrolytes, creatinine, osmolality, and 24-hour urine collection for protein, microalbumin, β2-microglobulin, creatinine, and electrolytes were done in pts with abnormal urine samples. There were 101screened pts (53 males; 76 SS, 20 SC, 3Sβ⁰, and 2 Sβ ⁺). Nineteen pts had MA detected by random urine. MA was confirmed in 24-hour samples in 46% of studied pts. In addition to MA, tubular proteinuria (increased β2-microglobulin) was detected in 1 pt, isolated hematuria in 3 and increased urine protein/creatinine (>0.2) in 4. From the MA+ pts, 15 had SS (19.7% of SS group) and 4 had SC (20% SC group). 25% of children 10 yrs of age or older had MA (mean± standard deviation MA 2.83±3.94), as compared to 6% of younger children (mean 1.21±0.80), (p=0.02). African Americans had lower incidence of MA (11.4%), compared to other children of Haitian (21.3%), Hispanic Caribbean (25%), and other Caribbean (28.5%) descent (p=not significant [NS]). There was no correlation between MA and history of stroke, acute chest syndrome/asthma, brief use of non-steroidal anti-inflammatory medications, hemoglobin or white cell values. From the subgroup of 16 pts on hydroxyurea, 11 were 10 yrs of age or older; of these, 5 (45.5%) had MA, compared to 21% of the same age non-treated group (p=NS). We analyzed the effect of age at onset of chronic transfusions and presence of MA. Six transfused pts had MA (age at start of transfusion 8.6–13.5 yrs, mean 11 yrs; mean MA 5.3±3.4), while there were 15 MA free pts (age 0.8–12.4 yrs, mean 7 yrs; mean MA 1.4±0.6), suggesting that early age at start of chronic transfusions may be protective for MA (p=0.0004). We conclude that: (1) urine screening of children with sickle cell hemoglobinopathies 10 yrs or older is recommended, (2) chronic transfusions starting at an early age may protect against MA, and (3) validity of random versus 24-hour urine collections in determining MA should be further investigated. Studies to further define the risk factors, prognosis, and intervention in children with sickle cell hemoglobinopathies are warranted.