Background Axial type of Spondyloarthropathy (SpA) can be subdivided into the (early) non-radiographic type and the radiographic type, which is equivalent to the diagnosis of Ankylosing Spondylitis. The proportion of nonradiographic axial SpA (nr-SpA) patients among those with newly diagnosed axial SpA ranges between 23 to 80%. 1 MRI proven sacroiliitis is the “gold standard” for the diagnosis of nr-SpA. But, we have seen in some previous studies that USG can be a reliable substitute to MRI for detecting sacroiliitis in non-radiographic Spondyloarthropathy (SpA). According to a study done by Ghosh et al, 29 radiographically negative patients fulfilling the definition of IBP (ASAS 2009) & 32 age and sex matched controls were made to undergo MRI and USG of their SI joints. 2 A significant difference in the number of USG documented Flow Signals (FS) of the SI joint (p<0.0001) between MRI proven cases and controls had been observed and a ROC analysis revealed a cut off value of 3 FS for optimum sensitivity and specificity of detecting sacroiliitis (sensitivity 90% & specificity 92.7%).
Objectives To assess changes in ultrasound features of sacroiliitis after NSAID use in patients with non-radiographic SpA, to compare the changes with that of MRI after treatment and to see whether Colour Doppler Ultrasound can help in monitoring disease activity.
Methods 35 patients diagnosed with non radiographic spondyloarthropathy based on inflammatory low back pain and MRI proven sacroiliitis, were made to undergo a baseline USG of sacroiliac (SI) joints. They were then kept on NSAIDs for a duration of 3 months. After 3 months, USG and MRI of sacroiliac joints were repeated and the both compared. USG findings at baseline and at follow up were also correlated with BASDAI.
Results A Wilcoxons signed rank test was done to compare the number of flow signals on USG of SI joint at baseline and after 3 months of treatment and p value was found to be significant (p<0.05), which means that vascularity of SI joints significantly decreases with NSAID. Number of flow signals in SI joint also correlated well with BASDAI at baseline (Spearman's rho correlation coefficient =0.632) and at follow up (Spearman's rho correlation coefficient =0.701). However, MRI at baseline and follow up were same and could not assess change with NSAID nor could it predict disease activity.
Conclusions Ultasonography of SI joint is a sensitive way of assessing response to NSAID use in Spondyloarthropathy patients and may be used as an objective tool in monitoring disease activity.
Sieper J, van der Heijde D. Non-radiographic Spondyloarthritis: New definition of an old disease. Arthritis & Rheumatism 2013 March; 65(3): 543–551.
Ghosh A,Mondal S,Sinha D, Nag A, Chakraborty S. Ultrasonography as a useful modality for documenting sacroiliitis in radiographically negative inflammatory back pain: a comparative evaluation with MRI. Rheumatology (2014); 53 (11):2030-2034.
Acknowledgements Dr. Sumit Chakraborty, Department of Radiology, IPGME&R, Kolkata, West Bengal.
Disclosure of Interest None declared