[Seasonal change in blood concentration of uric acid and its potential clinical implications]

To determine whether uric acid in plasma of patients registered at a PCC varies with the season.

Descriptive study, with two transversal cuts, one in winter and one in summer.

Health district on the outskirts of Valencia.

Selected at random from all patients over 18 with medical records, with appointments in January-February and July-August 1999. Sample size was calculated for paired data with an alpha error of 0.05 and beta error of 20%. The pertinent level of uraemia was set at 0.4 mg/dl. Variability was deduced from a mini-sample of 17 cases in a sample of 72 patients. The following were recorded: sex, age, BMI, blood count, glucaemia, total cholesterol, HDL-c, LDL-c, uric acid and triglycerides. Meteorological data were supplied by the Valencia Weather Centre.

Temperature (12.8 degrees C versus 25.8 degrees C), sun (9.9 hours a day versus 5.9) and relative humidity (67.1% versus 61.4%) were greater in summer than in winter. There were no differences in mean atmospheric pressure (760.1 mmHg versus 760.7). 75 patients with a mean age of 63 finished the study. Mean uric acid was higher in summer at 5.64 mg/dl (95% CI, 5.29-5.99) than in winter at 5.23 mg/dl (CI, 4.92-5.56). We found no significant differences in the BMI, red corpuscles, haematocrits, glucaemia, total or divided cholesterol, or triglycerides.

Seasonal variation in the plasma concentration of uric acid was found in the sample studied.