Renal hypouricemia is an ominous sign in patients with severe acute respiratory syndrome.

Background: The purpose of this study is to determine the incidence and significance of hypouricemia in patients with severe acute respiratory syndrome (SARS). Pulmonary lesions in patients with SARS are thought to result from proinflammatory cytokine dysregulation. Acute renal failure has been reported in patients with SARS, but whether cytokines can injure renal tubules is unknown.

Methods: Sixty patients diagnosed with SARS in Taiwan in April 2003 were studied. Patients were identified as hypouricemic when their serum uric acid (UA) level was less than 2.5 mg/dL (<149 micromol/L) within 15 days after fever onset. Urine UA and creatinine levels were available for 43 patients; the serum cytokines interleukin-6 (IL-6), IL-8, and tumor necrosis factor-alpha (TNF-alpha) were measured in 16 patients.

Results: Sixteen patients (26.7%) had hypouricemia (UA, 1.68 +/- 0.52 mg/dL [100 +/- 31 micromol/L]). No differences in age, sex, symptoms, vital signs, hemogram, or other biochemistry data existed between the hypouricemic and normouricemic groups. Fractional excretion (FE) of UA (FE UA) in 12 hypouricemic patients was 39.6% +/- 23.4%, significantly greater than that of 31 normouricemic patients (16.4% +/- 11.4%; P < 0.0001). After adjustments for age and sex, high FE UA was significantly associated with the lowest blood oxygenation (P = 0.001; r = -0.624). The number of catastrophic outcomes (endotracheal intubation and/or death) adjusted for older age and sex showed that hypouremic patients had an odds ratio of 10.57 (confidence interval, 2.33 to 47.98; P = 0.002). Kaplan-Meier curves for catastrophic outcome-free results showed significant differences between patients with normouricemia or hypouricemia (P = 0.01). Serum IL-8 levels correlated significantly with FE UA (P < 0.001; r = 0.785) and inversely with serum UA level (P = 0.044; r = -0.509); neither IL-6 nor TNF-alpha level showed such correlations.

Conclusion: One fourth of patients with SARS developed hypouricemia, which might result from a defect in renal UA handling and was associated with a high serum IL-8 level. Renal hypouricemia is an ominous sign in patients with SARS.