Rodrigues F, et al. J Korean Med Sci. 2023 Oct;38:e326. https://doi.org/10.3346/jkms.2023.38.e326

Objectives Hospitalisation is a risk factor for flares in people with gout. However, the predictors of inpatient gout flare are not well understood. The aim of this study was to develop a prediction model for inpatient gout flare among people with comorbid gout. Methods We used data from a retrospective cohort of hospitalised patients with comorbid gout from Wellington, Aotearoa/New Zealand, in 2017 calendar year. For the development of a prediction model, we took three approaches: (A) a clinical knowledge-driven model, (B) a statistics-driven model and (C) a decision tree model. The final model was chosen based on practicality and performance, then validated using bootstrap procedure. Results The cohort consisted of 625 hospitalised patients with comorbid gout, 87 of whom experienced inpatient gout flare. Model A yielded 9 predictors of inpatient gout flare, while model B and C produced 15 and 5, respectively. Model A was chosen for its simplicity and superior C-statistics (0.82) and calibration slope (0.93). The final nine-item set of predictors were pre-admission urate >0.36 mmol/L, tophus, no pre-admission urate-lowering therapy (ULT), no pre-admission gout prophylaxis, acute kidney injury, surgery, initiation or increase of gout prophylaxis, adjustment of ULT and diuretics prior to flare. Bootstrap validation of the final model showed adequate C-statistics and calibration slope (0.80 and 0.78, respectively). Conclusion We propose a set of nine predictors of inpatient flare for people with comorbid gout. The predictors are simple, practical and are supported by existing clinical knowledge.

Objectives The aim of this study was to determine the effect of antituberculous drugs on serum uric acid (SUA), urine uric acid (UUA) excretion, and renal function. Methods Patients with tuberculosis requiring a 6-month treatment course of antituberculous drugs (isoniazid, rifampicin, pyrazinamide, and ethambutol for 2 months, followed by isoniazid and rifampicin for a further 4 months) were included in this study. Serum uric acid, 24-hour UUA excretion, uric acid clearance (UACl), serum creatinine, and creatinine clearance were determined at baseline and at the end of the second week, second month, and fourth month. Results Sixteen of 50 patients completed the study. Their mean ± SD baseline SUA and UACl was 4.44 ± 1.72 mg/dL and 8.77 ± 7.03 mL/min per 1.73 m², respectively. At the second week, a significant increase in SUA (9.78 ± 3.21 mg/dL, P < 0.001) and significant decrease in UACl (3.50 ± 2.50 mL/min per 1.73 m², P = 0.001) were noted. These changes persisted through the second month, but returned to baseline value at the fourth month. Thirteen patients (81.25%) had hyperuricemia. The 24-hour UUA followed the same pattern as that of UACl but showed no statistical significance. There were no changes in serum creatinine or creatinine clearance. One patient had arthralgia, and another developed tuberculous arthritis. Conclusions The hyperuricemic effect of pyrazinamide and ethambutol was due primarily to a decrease in UACl, which was reversible, and had no negative effect on the renal function. Arthralgia was uncommon and required no specific treatment.

The objective of this study was to investigate the hypouricemic effects of green tea extract (GTE) in healthy individuals. This study comprised 1-week control, 2-week interventional, and 1-week follow-up periods. Participants were assigned randomly at the interventional period to consume GTE at 2 (GTE2), 4 (GTE4), or 6 (GTE6) g/d. Levels of serum uric acid (SUA), uric acid clearance, and serum antioxidant power (using trolox equivalent antioxidant capacity assay) were measured at both ends of each study period. Of 30 participants, 11, 11, and 8 received GTE2, GTE4, and GTE6, respectively. After 2 weeks of consumption, the mean SUA level tended to decrease in all groups, with no statistical significance. Serum uric acid reduction was greatest in GTE2 (from 4.81 ± 0.81 mg/dL to 4.64 ± 0.92 mg/dL, 3.53%). Uric acid clearance decreased significantly in GTE2 (from 11.37 ± 6.41 mL/min per 1.73 m to 7.44 ± 2.74 mL/min per 1.73 m, 34.56%, P < 0.05) and GTE4 (from 8.36 ± 3.41 mL/min per 1.73 m to 5.78 ± 2.33 mL/min per 1.73 m, 30.86%, P < 0.05). Serum antioxidant capacity (TEAC) increased significantly in GTE6 (from 32.77 ± 3.39 mg/mL to 35.41 ± 3.17 mg/mL, 8.06%, P < 0.05). There was no significant change in creatinine clearance. Gastrointestinal adverse events were common, but usually mild, with no medical treatment required. Green tea extract may modestly lower SUA level and decreases uric acid clearance. Green tea extract also significantly elevated serum antioxidant capacity with a positive dosage effect. The effect of GTE on SUA in healthy individuals was short term. The effects of GTE on urate handling in patients with hyperuricemia or gout need to be determined.

Currently, there are 5 existing classification criteria for gout: the Rome, New York, American Rheumatism Association (ARA), Mexico, and Netherlands criteria. This study was carried out to determine the performance of these classification criteria in Thai patients presenting with acute arthritis.All consecutive patients presenting with acute arthritis and being consulted at the Rheumatology Unit, Chiang Mai University Hospital from January 2013 to May 2015 were invited to join the study. Gout was defined by the presence of monosodium urate crystals in the synovial fluid or tissue examined by experienced rheumatologists. The 5 existing gout classification criteria were performed and evaluated in all of the patients, who were divided in subgroups of early disease (≤2 years), established disease (>2 years), and those without tophus.There were 136 gout and 97 nongout patients. Sensitivity and specificity across all criteria ranged from 75.7% to 97.1% and 68.0% to 84.5%, respectively. Overall, the Mexico criteria had the highest sensitivity (97.1%), and the ARA survey criteria the highest specificity (84.5%), whereas the Mexico criteria performed well in early disease with sensitivity and specificity of 97.1% and 81.7%, respectively. All 5 criteria showed high sensitivity (from 76.4% to 99.1%) but low specificity (from 30.8% to 65.4%) in established disease. In patients without tophus, the sensitivity and specificity ranged from 64.1% to 95.7% and 68.8% to 85.4%, respectively. The ARA survey criteria across all groups showed consistently high specificity for gout.The 5 existing classification criteria for gout had limited sensitivity and specificity in Thai patients presenting with acute arthritis. The ARA survey criteria are the most suitable for diagnosing gout in Thai people when crystal identification is not available.