Allopurinol underdosage in Danish primary care: a 2-year cohort study of patients with gout, including those with chronic kidney disease

While the majority of patients with gout are managed within primary care settings, up to one-quarter will progress to tophaceous gout within a decade. Tophaceous gout is associated with significant complications and frequently necessitates hospitalization. The risk of progression to tophaceous stage increases substantially as renal function declines. Although effective urate-lowering therapy (ULT) can prevent the formation of tophi, historical concerns regarding serious adverse effects, coupled with conflicting clinical guidelines have hindered the optimization of allopurinol dosing in patients with chronic kidney disease (CKD). This study evaluated adherence to guideline-recommended urate-lowering management in primary care following a hospital-confirmed diagnosis of gout, in both patients with and without moderate or severe CKD. We analyzed a retrospective, prospectively assembled cohort of consecutive gout patients, with and without CKD. Following a hospital-based gout diagnosis, all patients were transitioned back to primary care. We assessed maintenance of recommended SU targets (< 0.36 mmol/L for general gout management; <0.30 mmol/L for tophaceous gout) two years post-diagnosis. Registries enabled complete capture of SU measurements and ULT utilization across hospital and primary care settings. Of the 256 surviving patients, 47 (18%) had no recorded SU levels at follow-up, and 41 (16%) received no ULT. Among the remaining 215 patients receiving ULT, 202 were treated with allopurinol, 11 with febuxostat, and 2 with probenecid. Overall, 143 (68%) of the 209 surviving patients maintained the recommended and measured SU level of < 0.36 mmol/L. No serious side effects occurred in 78 with CKD, of whom 54 (69%) achieved target SU level. Among the 82 patients with tophaceous gout, only 39 (48%) achieved the stricter target of < 0.30 mmol/L, with no significant difference between CKD (47%) and non-CKD (48%) patients. In this Danish real-world primary care setting, a substantial proportion of patients with gout, regardless of CKD status, failed to maintain necessary SU targets to impede disease progression. Undertreatment was particularly pronounced among those with tophaceous gout. Insufficient allopurinol dose escalation, emerged as a common and modifiable barrier in this high-risk population.