Changes in urinary uric acid excretion in obstructive sleep apnea before and after therapy with nasal continuous positive airway pressure.
OBJECTIVE
To assess the utility of urinary uric acid excretion as a marker of nocturnal hypoxia in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) before and after the institution of nasal continuous positive airway pressure (CPAP).


METHODS
Prospective, open.


METHODS
Sleep Disorders Laboratory, Veterans Affairs Medical Center.


METHODS
Thirty consecutive male subjects, 20 with OSAHS and 10 without OSAHS.


METHODS
Spot morning urine and venous blood samples were obtained in all subjects; samples were also obtained after the application of CPAP in those with OSAHS. Uric acid excretion, normalized to creatinine clearance, was calculated as the product of urinary uric acid and serum creatinine concentrations divided by urine creatinine concentration. In patients with OSAHS, uric acid excretion was 0.55+/-0.1 mg/dL before CPAP therapy and decreased to 0.30+/-0.01 mg/dL after CPAP therapy (p < 0.001). The latter value did not differ significantly from the mean value (0.32+/-0.03 mg/dL) in the control group. Uric acid excretion in OSAHS patients correlated significantly with the apnea-hypopnea index (r=0.42; p<0.0003).


CONCLUSIONS
Uric acid excretion is increased in OSAHS patients and normalizes after CPAP treatment, most likely reflecting differences in tissue oxygenation between the two conditions. Further studies in large number of patients may confirm the usefulness of this simple test for diagnosis and follow-up of patients with OSAHS.
Sahebjani
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Veterans Affairs Medical Center, Department of Medicine, University of Cincinnati College of Medicine, Ohio 45220, USA.
D003404:Creatinine / Q000097:blood / Q000652:urine; D006801:Humans; D000860:Hypoxia / Q000652:urine; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012891:Sleep Apnea Syndromes / Q000097:blood / Q000628:therapy* / Q000652:urine; D014527:Uric Acid / Q000097:blood / Q000652:urine*
D014527:Uric Acid; D003404:Creatinine