Serum uric acid and related factors in 500 hospitalized subjects

The study purpose was to determine the following in a large sample of hospitalized patients: (1) the prevalence of hyperuricemia, (2) the association of hyperuricemia with other metabolic disorders, and (3) the factors independently predicting hyperuricemia. Five hundred adult patients (250 men and 250 women) were randomly selected from those admitted as inpatients over a period of 5 months. In all patients, body mass index (BMI), blood pressure, and serum glucose, lipid, creatinine, urea nitrogen, and urate concentrations were measured. The presence of diseases or use of medications known to affect serum urate levels were recorded. The mean level of serum urate was 5.6 mg/dL in the whole sample, 6.0 mg/dL in men and 5.3 mg/dL in women (P = .003, men v women). The prevalence of hyperuricemia was 27.6% (28.8% and 26.4% in men v women, P = nonsignificant). A definite or probable secondary hyperuricemia was found in 87.7% of the subjects. Hyperuricemia was rarely isolated (21%), whereas it was frequently associated with hypertension (60.1%), hyperlipidemia (31.2%), diabetes (28.3%), and obesity (21.7%). In 26.8% of the subjects, hyperuricemia was associated with two metabolic disorders, in 13.8% with three, and in 2.9% with four. Multiple metabolic disorders (three to four) were found in 16.7% of subjects with hyperuricemia. Serum urate levels progressively increased across a range of subjects from those without diabetes, hyperlipidemia, hypertension, or obesity to those with one, two, or a greater number of associated metabolic abnormalities. Multiple stepwise regression analysis showed that 43% of serum urate variability was explained by urea nitrogen levels, triglyceride levels, diuretic therapy, the inverse of creatinine (as an index linearly related to creatinine clearance), and BMI. These results indicate that in hospitalized subjects, hyperuricemia is (1) frequent, (2) a secondary phenomenon in most cases, and (3) frequently associated with other metabolic disorders. The major predictors of high serum urate levels are BMI, triglycerides, parameters of renal function, and use of diuretics. These variables explain a large proportion of serum urate variability.