Accuracy of dual-energy computed tomography (CT), ultrasound, cone-beam CT, and spectral photon-counting CT for detecting calcium crystal deposition in the osteoarthritic hand: a cross-sectional diagnostic test study

OBJECTIVE: To evaluate the diagnostic performance of dual-energy computed tomography (DECT), ultrasound (US), cone-beam computed tomography (CBCT), and multi-energy spectral photon-counting computed tomography (SPCCT) for detecting calcium pyrophosphate (CPP) and hydroxyapatite crystal deposition. METHOD: We prospectively enrolled patients scheduled for finger-joint surgery due to osteoarthritis. Preoperative cross-sectional assessment included visual analogue scale pain, and in vivo index tests with DECT, US, and CBCT; the postoperative ex vivo index test was SPCCT of excised joint material. Reference tests comprised compensated polarized light microscopy of synovial fluid and histology with Alizarin Red S staining of excised joint material. Tests for crystals were scored on a binary basis. We calculated sensitivity, specificity, and likelihood ratios (LRs); a test with positive LR > 10 or negative LR < 0.1 was considered 'very good'. RESULTS: We included 12 participants, nine of whom had at least one positive reference test for calcium crystals. None of the index tests met our predefined cut-offs for a very good test. The best sensitivity and specificity were 0.29 [95% confidence interval (CI) 0.04-0.71] and 0.67 (0.09-0.99) for DECT, 0.89 (0.52-1.00) and 1.00 (0.16-1.00) for US, 0.33 (0.07-0.70) and 0.67 (0.09-0.99) for CBCT, and 1.00 (0.66-1.00) and 0.00 (0.00-0.98) for SPCCT. Wide CIs reflected the small sample size. Participants with CPP in the synovial fluid had more pain than those without. CONCLUSION: SPCCT and US had high sensitivity for calcium crystal detection, although no test achieved the strict definition of a very good test. TRIAL REGISTRATION: ClinicalTrials.gov (NCT04585113).