In patients with acute mono/oligoarthritis, a targeted ultrasound scanning protocol shows great accuracy for the diagnosis of gout and CPPD

Objectives: To determine an ultrasound (US) scanning protocol with the best accuracy for the diagnosis of gout and CPPD in patients with acute mono/oligoarthritis of unknown origin. Methods: Patients with acute mono/oligoarthritis, in whom a joint aspiration at the most clinically involved joint (target joint) was requested, were consecutively enrolled. US was performed in each patient before the arthrocentesis. The accuracy of different US findings and scanning protocols for the diagnosis of gout and CPPD was calculated. Results: 161 subjects were included (32 gout patients, 30 CPPD patients and 99 disease-controls).US findings had a high specificity for gout (0.92-0.96) and CPPD (0.90-0.97), while the sensitivity ranged from 0.73 to 0.85 in gout (double contour sign and tophi, respectively) and from 0.60 to 0.90 in CPPD (hyaline and fibrocartilage deposits, respectively). The US assessment of two joints bilaterally (gout: knees, MTP1js, CPPD: knees, wrists) + the target joint had an excellent diagnostic sensitivity (gout:0.91, CPPD:0.93) and specificity (gout:0.91, CPPD:0.89). This targeted US scanning protocol yielded to higher diagnostic accuracy compared to the US evaluation of the target joint (gout, AUC:0.91 vs AUC:0.84, p = 0.03; CPPD, AUC:0.93, vs AUC:0.84, p = 0.04) unless the target joint was the knee or the MTP1j in gout, and the knee or the wrist in CPPD. Conclusions: A targeted US scanning protocol of two joints bilaterally + the target joint (unless this was the knee, MTP1j or the wrist) showed an excellent accuracy (>90%) for the diagnosis of crystal arthritis in patients with acute mono/oligoarthritis.