K. Van Leeuwen, AM. Bohnen, H. Janssens, SMA. Bierma-Zeinstra
Department of General Practice, Erasmus Medical Center, Rotterdam, The Netherlands
Introduction: Gout is the most common inflammatory arthritis in the Dutch primary care population. The Dutch Guidelines for general practitioners recommends urate lowering therapy (ULT) with allopurinol if gout flare frequency is unacceptable from the patients’ perspective (e.g. more than three flares per year) or in the presence of tophi. Primary treatment target is an acceptable gout flare frequency, given a lowered serum uric acid (SUA) level of at least <0.35 mmol/L. However, there is limited evidence from randomized trials or observational studies for the effectiveness of allopurinol preventing gout flares if compared to the clinical course without ULT.
Objectives: What are the clinical characteristics of patients with gout in primary care and how are they treated with allopurinol? Status All participants have completed the first year of the two year follow up period. There are intentions for extending the follow up period to assess patient related determinants for successful gout management in primary care and also collecting DNA-samples.
Methodology: We designed a primary care, prospective observational cohort study in the Netherlands. Between February 2017 and October 2018 patients were included (aged ≥ 18 years) who according to their medical records had at least one morbidity code of gout in the period 2013-2015. Baseline measurements included blood pressure, height and weight and a blood sample (i.a. eGFR and SUA). During two year follow up, every 3 months the participants received questionnaires with questions about gout attack frequency, medication use and general health. Findings In 118 general practices, 838 patients with a morbidity code of gout were included. Of them 753 completed the baseline questionnaire (86% male; average age 66 years [SD 11.0]). Participants were known with gout for median 6.7 years (IQR 3.3-13) and experienced median 8 gout flares during that period (IQR 4-20). Tophi were reported by 8% of the patients. In the year preceding the baseline 55% of the participants had had at least one gout flare, and 51% of the patients did not visit their GP during the most recent gout flare. In this cohort, 274 participants (36%) used allopurinol at baseline, median since 3 years (IQR 1-6). The used daily dose was known for 249 patients: 81 patients used 100mg, 63 patients used 200mg, 90 patients used 300mg per day, and 15 patients used more than 300mg per day. The laboratory results showed a mean SUA of 0.43 mmol/L (SD 0.10), and 75% of the participants had a raised SUA level (>0.35 mmol/L), 48% of the allopurinol users and 90% of the non-users. In the first year of follow up 19% of the allopurinol-users and 32% of the non-users reported more than three gout attacks.
Significance: These first results show that primary care patients have more gout flares than registered in the medical records. This may indicate undertreatment of patients with an indication for ULT, who don’t receive ULT, or who use ULT, but probably in an insufficient dosage. Next, to compare the association of gout flare frequency with allopurinol use, we will apply propensity score matching as far as possible for allopurinol users and non-users. Then, using Poisson regression we aim to calculate the corrected estimated effect of allopurinol on the number of self-reported gout flares. We also will attempt to assess effects of diet, lifestyle and medication use. Further results are expected in the course of 2020.