Background: Gout is a condition that is commonly diagnosed and treated in hospitalized patients. The gold standard for diagnosis of gout is identification of negatively birefringent, needle shaped uric acid crystals within neutrophils in fluid obtained by joint aspiration of affected joints. There have been a number of small studies that have shown serum uric acid levels may be normal during an acute gout flare however despite this, it is one of the most commonly obtained labs in an acute gout flare.
Methods: Data was obtained from the HCA South Atlantic Enterprise data warehouse (EDW) between the years of 2016 and 2018. Emergency department visits and hospitalizations for acute gout were identified using International Classification of Diseases-10 Clinical Modification (ICDM-10) codes relating to acute gout. The primary outcome was uric acid level (units: mg/100 mL) less than 6, between 6 and 8, and greater than 8. The independent variable was whether or not the patient had an ICD 10 diagnosis of acute gout. The dependent variable was serum uric acid level. Other variables of interest included age, sex, history of chronic gout, BMI, history of HTN, and history of kidney disease. A chi-square test of the data was performed.
Results: Of 4597 patients with a diagnosis of non-chronic gout identified, 781 (16.9%) patients had a serum uric acid level documented. The average age of all patients with a diagnosis of non-chronic gout identified was 63.5. 54.23% of these patients were white, 41.64% of these patients were black, and 4.13% were documented as “other”. Of the patients with a documented serum uric acid level, 35.2% had a serum uric acid between 6 and 8, 36.2% had had serum uric acid levels greater than 8, 28.6% had serum uric acid levels less than 6. These differences were not statistically significant (p=0.9684). This translates to a sensitivity of 36% when using serum uric acid for diagnosis of acute gout.
Conclusions: Serum uric acid is not a sensitive test for diagnosis of an acute gout flare. This greatly limits the clinical utility of obtaining a serum uric acid level during an acute gout flare.