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Indicators of Renal Glomerular and Tubular Functions in Patients with Beta-Thalassaemia Major: A cross sectional study at the Royal Hospital, Oman.

OBJECTIVES
There are limited data concerning the assessment of renal function in beta-thalassaemia major, with no study of such involvement in Omani patients. The objective of this study was to establish the pattern of renal glomerular and tubular function using traditional and specific laboratory tests in patients with beta-thalassaemia major.


METHODS
This cross-sectional study, from January-July 2008, included 30 patients of the Thalassaemia Clinic at the Royal Hospital, Oman, with transfusion-dependent homozygous beta-thalassaemia major. They included 15 males and 15 females, aged 16-32 years with mean ± standard deviation of 21.23 ± 3.42 years. The medical records were reviewed and renal function states assessed as follows: serum creatinine, estimated glomerular filtration rate (eGFR); urea; phosphate, fractional excretion of filtered sodium (FENa); urine albumin: creatinine index; urine ß2-microglobulin:creatinine index; tubular reabsorption of phosphate (TRP), and tubular maximum phosphate reabsorption (TmP)/GFR.


RESULTS
All patients had eGFR >90 ml/min/1.73m(2); serum creatinine <90 μmol/L; serum urea <6.0 mmol/L, and urine albumin:creatinine <2.5 mg/mmol. Only 2 (6.7%) patients had FENa >1% and 3 (10.0%) patients had urine ß2-microglobulin: creatinine >22 μg/mmol. All patients had TRP >0.85, of whom seven (23.3%) patients had values within the range of 0.85-0.95 and 23 (76.7%) had values >0.95. Also, all patients had TmP/GFR >1.0 mmol/L, of whom only one (3.3%) patient had TmP/GFR of 1.0-1.5, and 29 (96.7%) patients had TmP/GFR >1.5 mmol/L. Finally, 24 (80%) patients had serum phosphate >1.4 mmol/L. Linear regression revealed a highly significant correlation between serum phosphate and TmP/GFR (r = 0.904, P < 0.001).


CONCLUSION
Renal function, glomerular and tubular, appears to be well preserved in beta-thalassaemia major. Almost all renal function indicators were within the recommended ranges. Raised TmP/GFR and TRP were noted in the majority of patients, reflecting an up-trend in serum phosphate and therefore increasing renal phosphate reabsorption.