Diagnostic accuracy of dual-energy computed tomography (DECT) to differentiate uric acid from non-uric acid calculi: systematic review and meta-analysis.

BACKGROUND: Uric acid stone diagnosis is presently done primarily with in vitro analysis of stones. In vivo diagnosis with dual-energy CT (DECT) would allow earlier initiation of therapy with urine alkalinization and avoid surgical intervention.

OBJECTIVE: To evaluate if DECT, using stone analysis as reference standard, is sufficiently accurate to replace stone analysis for diagnosis of uric acid stones.

METHODS: Original studies in patients with urolithiasis examined with DECT with stone analysis as the reference standard were eligible for inclusion. MEDLINE (1946-2018), Embase (1947-2018), CENTRAL (August 2018), and multiple urology and radiology conferences were searched. QUADAS-2 was used to assess risk of bias and applicability. Meta-analyses were performed using a bivariate random-effects model.

RESULTS: A total of 21 studies (1105 patients, 1442 stones) were included. Fourteen studies containing 662 patients (944 stones) were analyzed in the uric acid dominant target condition (majority of stone composition uric acid): mean sensitivity was 0.88 (95% CI 0.79-0.93) and specificity 0.98 (95% CI 0.96-0.99). Thirteen studies (674 patients, 760 stones) were analyzed in the uric acid-containing target condition (< majority of stone composition uric acid): mean sensitivity was 0.82 (95% CI 0.73-0.89) and specificity 0.97 (95% CI 0.94-0.98). Meta-regression showed no significant variability in test accuracy. Two studies had one or more domains at high risk of bias and there were no concerns regarding applicability.

CONCLUSION: DECT is an accurate replacement test for diagnosis of uric acid calculi in vivo, such that stone analysis could be replaced in the diagnostic pathway. This would enable earlier initiation of urine alkalinization.

KEY POINTS: • DECT for uric acid dominant stones has sensitivity of 0.88 (95% CI 0.79-0.93) and specificity of 0.98 (95% CI 0.96-0.99); uric acid-containing stones had mean sensitivity of 0.82 (95% CI 0.73-0.89) and specificity of 0.97 (95% CI 0.94-0.98). • Meta-regression did not identify any variables (study design, reference standard, dual-energy CT type, dose, risk of bias) that influenced test accuracy. • Only 2 of the 21 included studies had 1 or more domain considered to be at high risk of bias with the majority of domains considered at low risk of bias; there were no concerns regarding applicability in any of the included studies.