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Renal reabsorption of phosphate in children with sickle cell anemia
N Al-Harbi1, S H Annobil, F Abbag
1Department of Child Health, College of Medicine, King Saud University-Abha Branch, Abha, Kingdom of Saudi Arabia.
Insights
Children with sickle cell anemia have lower serum phosphate and reduced renal phosphate reabsorption compared to healthy children. This contrasts with findings in adults with the condition.
Area of Science:
- Nephrology
- Pediatrics
- Hematology
Background:
- Adults with sickle cell anemia exhibit elevated serum phosphate and phosphate reabsorption.
- Renal phosphate handling in pediatric sickle cell anemia patients is not well-documented.
Purpose of the Study:
- To investigate renal phosphate handling in children with sickle cell anemia.
- To compare serum phosphate levels and tubular phosphate reabsorption between pediatric sickle cell anemia patients and healthy controls.
Main Methods:
- Assessed serum phosphate levels and calculated tubular phosphate reabsorption (TP/GFR) in 30 children with sickle cell anemia and 40 healthy controls.
- Utilized random urine and blood samples and the formula TP/GFR = Sp - Up x SCr: UCr.
- Ensured all participants had normal renal function.
Main Results:
- Young sickle cell anemia patients had significantly lower mean serum phosphate (4.3 mg/dl) than controls (5.3 mg/dl).
- Mean TP/GFR was significantly lower in young sickle cell anemia patients (4.09 mg/dl) compared to controls (4.65 mg/dl).
- Results indicate reduced renal phosphate reabsorption in pediatric sickle cell anemia.
Conclusions:
- Pediatric sickle cell anemia is associated with lower serum phosphate and TP/GFR, contrasting with adult findings.
- Elevated parathyroid hormone levels in sickle cell anemia may contribute to decreased phosphate reabsorption.
- Findings highlight age-dependent differences in renal phosphate handling in sickle cell anemia.
Abstract:
It has previously been reported that in adult patients with sickle-cell anemia the serum phosphate value and the maximum tubular reabsorption of phosphate per liter of glomerular filtrate (TmP/GFR) were significantly higher than in normal controls. This does not appear to have been studied in children with sickle cell anemia (young sicklers) and this prompted us to assess renal phosphate reabsorption in this group of patients. We looked at serum phosphate level and calculated renal phosphate reabsorption (TP/GFR) in children taking random urine and blood samples at the same time and using the formula TP/GFR = Sp - Up x SCr: UCr, in 30 young sicklers all of whom had normal renal function (mean age 7.3 years) and 40 normal matching controls (mean age 6.5 years). The mean serum phosphate value in young sicklers was significantly lower than in controls (4.3 against 5.3 mg/dl) while the mean value of TP/GFR was 4.09 +/- 0.74 mg/dl in young sicklers compared to 4.65 +/- 0.75 mg/dl in the control group (p = 0.0026). Therefore, the TP/GFR in young sicklers was also significantly lower (p = 0.0026) than in the control group. This may be explained by the high serum level of parathyroid hormone reported previously in patients with sickle cell anemia which is expected to lower phosphate reabsorption (TmP/GFR and TP/GFR are identical in children). The lower serum phosphate value and TP/GFR in younger sicklers seems to be in contrast with the relatively high serum phosphate value and TP/GFR previously reported in adults with sickle cell anemia.