Gout flares, serum urate and seasonality: a descriptive cohort study

To investigate the relationship between serum urate levels and gout flares and how these vary at different times of the year.

A cohort of people with incident gout was established using a large UK primary care database (Clinical Practice Research Database). Clinician-recorded gout flares and serum urate (SU) measurements were identified and described using joinpoint linear regression modelling. The relationship between SU level, flare frequency, month of the year and mean monthly temperatures was explored and correlations tested using Pearson correlation coefficients.

249,157 individuals (mean follow-up 6.7 years) experienced 417,101 flares and had 341,457 SU measurements (mean SU 437 µmol/L, standard deviation (SD) 106 µmol/L). SU levels peaked the day before a flare (487 µmol/L). Mean SU in the year preceding a flare was 474 µmol/L compared with 432 µmol/L in the year post-flare. SU levels did not near pre-flare levels in the year following a flare. Flares were most frequent, and SU was highest, in the summer months (June to August). The correlation co-efficient between flares and months of the year was 0.94, whereas the correlation with temperature was less strong (0.70).

SU measurement in the year following a gout flare is not indicative of the peak (pre-flare) SU levels that an individual may have experienced. Clinicians should consider this when considering SU measurements in the diagnosis of gout. Patients may find it helpful to be informed of the seasonality of gout flares and advised to take extra caution to reduce the risk of flares during summer months. Keypoints • Serum urate (SU) levels drop precipitously during gout flares and remain low for several months. • Correlations exist between flare rate and summer months, and with seasonal variation in SU levels. • Clinicians should be aware of how gout flares affect SU when interpreting SU levels.