Dual-energy CT may help clinicians diagnose gout when MSU crystals are not observed through polarizing microscopy.
Dual-energy CT (DECT) provides good diagnostic accuracy for detection of monosodium urate (MSU) deposits in patients with gout, according to a study published in the Annals of Rheumatic Diseases.
Researchers from the Mayo Clinic in Rochester, Minn., undertook a study to assess the accuracy of DECT for diagnosing gout. They also investigated whether the imaging could have an impact on clinical decision making, which is currently done with polarizing microscopy of synovial fluid.
Eighty-one patients participated in the study, 40 with active gout and 41 who had other types of joint disease. “Sensitivity and specificity of DECT for diagnosing gout was calculated against a combined reference standard (polarizing and electron microscopy of synovial fluid),” the authors wrote. “To explore the diagnostic yield of DECT scanning, a third cohort was assembled consisting of patients with inflammatory arthritis and risk factors for gout who had negative synovial fluid polarizing microscopy results.”
The findings showed that sensitivity of DECT was 0.90 and specificity was 0.83 in diagnosing gout. All false negative patients were observed among those with acute, recent-onset gout. All false positive patients had advanced knee osteoarthritis. Fourteen of 30 patients (46.7 percent) among the diagnostic yield cohort showed evidence of uric acid deposition.
The researchers concluded that DECT provided good diagnostic accuracy for detecting MSU deposits in patients with gout, but sensitivity was lower in patients who only recently developed gout. Clinicians could use DECT if they suspect gout but they do not see MSU crystals in the synovial fluid.