Diagnostic accuracy and trajectories of referrals for gout to rheumatology

Abstract

Objectives

To evaluate diagnostic accuracy and trajectories of gout referrals to rheumatology including factors associated with an accurate diagnosis.

Methods

We performed a retrospective cohort study of referrals at 4 rheumatology clinics in Brampton, Canada from December 2019 to January 2023. We assessed gout diagnostic accuracy referenced to the rheumatologist's “gold standard” diagnosis, describing alternative final diagnoses. Using multivariable logistic regression, we identified factors associated with an accurate gout diagnosis.

Results

Among 4315 patients, 216 were diagnosed with gout. Of 191 gout referrals (mean (SD) age 58.4 (15.4) years; 77.0% male), the diagnosis was unchanged in 159 (83.2%) patients with alternative diagnoses comprising osteoarthritis, autoimmune inflammatory arthritis and calcium pyrophosphate deposition disease. Referring physicians had moderate-to-high sensitivity (73.6%, 95% CI: 67.2–79.4), specificity (99.2%, 95% CI: 98.9–99.5), positive predictive value (83.2%, 95% CI: 77.2–88.2), negative predictive value (98.6%, 95% CI: 98.2–99.0) and inter-rater reliability (Cohen's kappa: 0.77, 95% CI: 0.72–0.82). Accuracy was highest amongst internists and emergency room physicians. Male sex (OR 14.32, 95% CI: 4.44–46.17), serum urate ≥ 500 μmol/L (OR 9.10, 95% CI: 2.19–7.78), lower extremity monoarthritis (OR 5.08, 95% CI: 1.59–16.27) and symptom duration ≤ 2 weeks (OR 3.87, 95% CI 1.23–12.21) were predictive of a final gout diagnosis.

Conclusions

Referring providers had reasonably high accuracy in diagnosing gout. Traditional risk factors were associated with concordance with the consultant rheumatologist. Suboptimal gout care likely does not stem at point-of-diagnosis and quality improvement efforts should be focused on mitigating treatment-associated care gaps.