Elevated calculated serum osmolality during acute gout attacks is associated with pain severity and systemic...

Acute gout attacks are characterized by intense inflammatory activity and pain. This study aimed to evaluate changes in calculated serum osmolality during acute gout attacks compared with the inter-flare period and to investigate its associations with pain severity and systemic inflammatory markers. In this retrospective paired observational study, 79 patients with gout were evaluated during an acute attack and again in the inter-flare period. Calculated serum osmolality, inflammatory markers, pain visual analog scale (VAS) scores, and the number of involved joints were recorded. Paired comparisons, correlation analyses, linear mixed-effects models for paired acute/inter-flare comparisons, and multivariable linear regression analyses restricted to the acute attack period were performed. Calculated serum osmolality was significantly higher during acute gout attacks compared with the inter-flare period (296.6 ± 6.1 vs. 291.8 ± 5.1 mOsm/kg; p < 0.001), accompanied by significant increases in inflammatory markers and leukocyte indices. During acute attacks, calculated serum osmolality correlated with pain intensity, joint involvement, CRP, ESR, WBC count, and neutrophil count, but not with serum uric acid. In adjusted mixed-effects models, the acute attack period remained independently associated with higher calculated serum osmolality (β=+4.9 mOsm/kg; 95% CI 3.6-6.2; p < 0.001). In multivariable linear regression analyses restricted to the acute phase, higher calculated serum osmolality was associated with higher inflammatory marker levels. Elevated calculated serum osmolality during acute gout attacks was associated with higher inflammatory markers and greater pain severity. Further prospective studies are needed to clarify the clinical relevance and potential pathophysiological implications of this association.