Association between serum free fatty acid levels and tophus in patients with gout: a cross‐sectional study

To explore the relationship between serum free fatty acid (FFA) and tophus in gout patients, and to investigate whether FFA increases the risk of tophus deposition by lowering urine pH.A total of 595 patients with gout aged 18 to 80 were enrolled between June 2018 and August 2021. The subjects were divided into four groups according to FFA. Logistic regression was used to analyse the association between serum FFA and tophus. Receiver operating curves (ROC) were plotted to explore the predictive value of FFA on the occurrence of tophus.Accompanying the increase of FFA levels, the prevalence of tophus in groups Q3 and Q4 was significantly higher than in groups Q1 and Q2 (33.6%, 36.5% vs. 6.3%, 19.6%, p<0.001). According to the Spearman correlation, serum FFA levels were positively correlated with tophus while negatively with urine pH (p<0.001). FFA had a significant interaction with urine pH on tophus risk. Multivariate logistic regression showed that participants in Q2-Q4 had a higher OR of tophus than those in Q1 (OR were 2.770, 5.878 and 7.958 in Q2-Q4, respectively). ROC showed the best cut-off value of serum FFA level in predicting the onset of tophus was 0.46 mmol/L. Serum FFA had a great discriminant ability to predict tophus.High FFA levels are independently associated with tophus risk and FFA may promote tophi deposition by lowering urine pH. Serum FFA levels have a great screening value to identify tophus.