Ultrasound of sacroiliac joints in spondyloarthritis: a systematic review

Ultrasound (US) is an accessible imaging technique with a possible role to diagnose active sacroiliitis, so this technique is projected as a promising diagnostic tool for the diagnosis of SpA. We analyse the available evidence about the use of US as a diagnostic tool in sacroiliitis in patients with SpA, by a systemic review of the literature fulfilling OMERACT criteria. A systematic literature search for original articles was carried out using four databases (Medline, Embase, Scopus and Web of Science). Data from studies were included only if participants had SpA and a US examination of sacroiliac joint (SIJ) was performed. The methodological quality of the studies was assessed using QUADAS-2 tool. Thirteen studies were included. All studies were observational, prospective and cross-sectional. In most articles (76.9%), the main US finding compatible with sacroiliitis evaluated was the presence of vascularisation (Doppler signals) with measurements of the resistive index (RI). The sensitivity and specificity analysis were performed in seven studies (58.8%) and were good, with a median of 90 and 89.2%, respectively. The studies showed a positive to moderate a strong correlation between the US and the gold standard but this was optimal only in four studies. In general, the agreement was good in all studies (≥ 0.80). The methods of evaluation of sacroiliitis vary between the studies included. To date, there is not enough evidence to support the use of ultrasound as a diagnostic method for sacroiliitis but it has potential to identify structural lesions at SIJ's level.