Gout Urate Cryst. Depos. Dis., Volume 3, Issue 3 (September 2025) – 4 articles

The 3rd Annual Meeting of the International Network on Ectopic Calcification (INTEC) was held in Faro, Portugal on 12–13 September 2024. This hybrid meeting brought together researchers and clinicians focused on the molecular, (patho)physiological, and clinical aspects of ectopic calcification in hereditary and acquired conditions, as well as in aging. The findings presented in this year’s meeting emphasised the complexity of the field, offering new insights into both mechanistic pathways and translational hurdles. The abstracts of this year’s meeting are collected in this conference paper, with permission from the corresponding authors. Full article

The evidence regarding allopurinol’s effects on renal function among people with hyperuricemia and gout has been conflicting, though clinicians are often cautious about using allopurinol in chronic kidney disease (CKD). We sought to examine the relation between allopurinol use in those with gout and CKD and the risk of worsening renal function. We conducted a time-stratified propensity score (PS)-matched cohort study on the IQVIA Medical Research Data representative of the UK general population. Among participants 18–89 years old with gout and CKD 3–4 not on urate-lowering therapy within one year prior, we identified new users of allopurinol and matched them 1:1 with a non-user. We analyzed the relation between incident allopurinol use and the changes in the eGFR at one year of follow-up using linear regression adjusted for the potential confounders included in the PS model. We PS-matched 10,716 allopurinol initiators to 10,716 non-users, among whom 42% were female, the mean age was 74 years and 7% had CKD4. The progression to dialysis or kidney transplant was similar in both groups. The mean eGFR prior to the study entry was 48.4 mL/min among allopurinol initiators and 49.5 mL/min among non-users, while the last eGFR within one year was 49.4 and 49.7 mL/min, respectively. The allopurinol initiators had an adjusted mean increase in the eGFR of 0.81 mL/min (95% CI 0.57–1.05) greater than that of non-users. Among those with gout and CKD 3–4, allopurinol did not worsen renal function and may have slightly improved it, suggesting that allopurinol is not detrimental to patients with gout who have CKD. Full article

Objectives: Identification of monosodium urate (MSU) and calcium pyrophosphate (CPP) crystals in synovial fluid should ideally be performed within 24 h to ensure optimal diagnostic accuracy for gout and CPP arthritis. However, crystal identification is often delayed in community-based healthcare facilities due to limited access to specialists or necessary equipment. This study aimed to determine whether MSU and CPP crystals remain detectable in synovial fluid after two weeks of storage at 4 °C and −20 °C. Methods: Anonymized synovial fluid samples were obtained from Thammasat University Hospital between February and March 2024. All samples underwent an initial round of crystal identification using compensated polarized light microscopy, conducted by two experienced examiners blinded to the clinical diagnosis. Following the initial analysis, each sample was divided into two equal portions and placed in ethylenediaminetetraacetic acid (EDTA)-coated tubes. One portion was stored at 4 °C, while the other was frozen at −20 °C. After two weeks, all samples underwent a second round of crystal identification. Results: Forty-nine samples were included for the first evaluation; MSU and CPP crystals were identified in 14 and 6 samples, respectively. On the second examination, MSU crystals were detectable in 13/14 (92.8%) samples stored at 4 °C and 12/14 (85.7%) samples stored at −20 °C. However, CPP crystals were detectable in 2/6 (33.3%) samples stored at both temperatures. No new crystal formation in initially negative samples was observed. Conclusion: MSU crystals remain detectable in synovial fluid for up to two weeks when stored in a standard refrigerator or freezer. However, the identification rate of CPP crystals tends to decline over this period. These findings may help inform best practices for handling synovial fluid samples in cases where immediate access to a specialist or necessary equipment is unavailable. Full article

Objectives: (1) To compare cytokine levels in participants with serum urate (SU) < 360 µmol/L, SU ≥ 360 µmol/L with and without monosodium urate (MSU) crystal deposition, respectively, and inter-critical gout. (2) To explore the association of IL-1β, IL-6 and high-sensitivity (hs) CRP with disease duration and the frequency of self-reported gout flares. Methods: Samples and data from 184 participants from studies conducted at Academic Rheumatology, Nottingham City Hospital, were included. Serum high-sensitivity CRP and cytokines involved in the pathogenesis of gouty inflammation were measured. MANCOVA and multivariate linear regression were used, as appropriate, and were adjusted for age, sex, body mass index and self-reported comorbidities. p values were adjusted for multiple testing using a 5% false-discovery rate. Results: Participants with inter-critical gout had greater levels of IL-1β (p_corr = 0.009), IL-18 (p_corr = 0.02), IL-6 (p_corr < 0.0001), IP-10 (p_corr < 0.0001), TNF-α (p_corr < 0.0001), GRO-α (p_corr = 0.0006) and hsCRP (p_corr = 0.009) compared to other groups in multivariate analyses and after correcting for multiple testing. There were no differences in cytokine and hsCRP levels in participants with SU < 360 µmol/L and in participants with SU ≥ 360 µmol/L with or without MSU crystal deposition. There was a statistically non-significant trend for association between IL-6 levels and number of self-reported gout flares. Conclusions: Our findings suggest that gout is a chronic inflammatory condition. The pre-clinical phases of gout were not associated with systemic inflammation, potentially due to the modest sample size. Further research is required to understand whether treating gout by targeting the complete dissolution of MSU crystals would reduce systemic inflammation in inter-critical gout. Full article