The use of feet/ankles or knees dual-energy computed tomography (DECT) alone provides the best overall accuracy compared to ultrasound or DECT/ultrasound combination in the diagnosis of patients with suspected gout, according to study results published in Rheumatology (Oxford).

Study authors sought to examine the accuracy of DECT compared to ultrasound or a combination of DECT and ultrasound in diagnosing gout.

They conducted a prospective study (EudraCT Identifier: 2020-A01269-30) in a single outpatient French rheumatology clinic at a tertiary care hospital in the CRYSTALILLE inception cohort. Between April 2016 and August 2019, prospectively collected data were used to study the accuracy of DECT or ultrasound alone, or their combination, based on anatomic site (feet/ankles and/or knees) for the diagnosis of gout. Two diagnostic standards for diagnosing gout were used: demonstration of monosodium urate (MSU) crystals in synovial fluid (gold standard) or modified (excluding DECT and ultrasound) 2015 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) gout classification criteria (silver standard).


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A total of 147 participants (mean age, 64.7±14.3 years) were enrolled in the study, including 92 patients who were newly referred to the rheumatology clinic for establishing a gout diagnosis and 55 patients who were referred to the clinic for assisting with their gout management. Overall, 86% of the participants were men; 26% of the patients had a disease duration of 2 years or less.

Participants underwent a combination of DECT and ultrasound of both their feet/ankles and knees. Data were obtained during clinical visits regarding demographics, gout symptoms to calculate ACR/EULAR gout classification criteria, comorbidities, serum urate levels, and treatments, along with imaging examinations.

Of the total cohort, 48 patients (33%) received synovial fluid analysis, with 38 testing positive for MSU crystals. Mean symptom duration was 9.2 years. Overall, 100 patients (68%) met the silver standard. Diagnostic accuracy statistics for feet/ankles DECT, feet/ankles ultrasound, knees DECT, and knees ultrasound were calculated, compared to the gold standard (sensitivity, 87%, 84%, 91%, and 58%, respectively; specificity, 100%, 60%, 87%, and 80%, respectively; negative predictive value [NPV], 67%, 50%, 70%, and 33%, respectively; and area under the receiver operating characteristic curve (AUC), 0.93, 0.72, 0.89, and 0.66, respectively).

On combining feet/ankles DECT with feet/ankles ultrasound or knees DECT with knees ultrasound, though a numerically higher sensitivity was achieved compared to DECT alone, the overall accuracy was lower. Similarly, combining imaging knees to feet/ankles also generated a numerically higher sensitivity and NPV compared to the use of feet/ankles DECT alone, without any differences in overall accuracy. These findings were replicated compared to use of the silver standard, but with lower values reported.

One of the main study limitations was the lack of generalizability.

Study authors concluded, “The main message for practitioners in rheumatology clinics from this study is that DECT alone ‒ particularly of the feet/ankles ‒ may offer the best overall performances for the diagnosis of patients with suspected gout.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Singh JA, Budzik JF, Becce F, Pascart T. Dual-energy computed tomography versus ultrasound, alone or combined, for the diagnosis of gout: a prospective study of accuracy. Rheumatology (Oxford). Published online January 7, 2021. doi:10.1093/rheumatology/keaa923