Two related studies on a group of 187 patients demonstrated high sensitivity of 90% to 92% and specificity of 94% to 97% for the diagnosis of AS by using global assessment of both inflammatory and structural lesions [83,87], and subsequently this group of authors showed that identifying erosions and/or bone marrow edema increases sensitivity for axSpA compared with bone marrow edema alone, without decreasing specificity [85]. They also showed that identifying erosions and/or bone marrow edema on MRI increased both sensitivity and specificity for axSpA compared with the diagnostic criterion of solely bone marrow edema [88]. Subchondral fatty deposition, another chronic finding of structural marrow remodeling, is an additional helpful and highly specific finding in axSpA with reported specificities up to 95% to 98% [89,90]. Finally, intra-articular signal changes including increased T1 signal, T2 hyperintense joint fluid, and ankylosis are highly specific findings for axSpA, and when found together with bone marrow edema can increase the positive predictive value for a diagnosis of axSpA compared with bone marrow edema alone [91,92]. Overall, it is clear that interrogation of sacroiliac joint MRI using both STIR and T1-weighted images is critical to identify both the inflammatory and structural changes of axSpA in clinical practice. MRI has long been considered inferior to CT in demonstrating the structural changes of axSpA, although evolving literature demonstrates that a specific MRI sequence, volumetric interpolated breath-hold examination (VIBE), can Inflammatory Back Pain demonstrate erosions with higher sensitivity and similar specificity compared to conventional T1-weighted imaging, and may be comparable to CT [93,94], making it a promising technique for identifying structural lesions of axSpA on MRI.
Inflammatory Back Pain Known or Suspected Axial Spondyloarthropathy PCAs. Two related studies on a group of 187 patients demonstrated high sensitivity of 90% to 92% and specificity of 94% to 97% for the diagnosis of AS by using global assessment of both inflammatory and structural lesions [83,87], and subsequently this group of authors showed that identifying erosions and/or bone marrow edema increases sensitivity for axSpA compared with bone marrow edema alone, without decreasing specificity [85]. They also showed that identifying erosions and/or bone marrow edema on MRI increased both sensitivity and specificity for axSpA compared with the diagnostic criterion of solely bone marrow edema [88]. Subchondral fatty deposition, another chronic finding of structural marrow remodeling, is an additional helpful and highly specific finding in axSpA with reported specificities up to 95% to 98% [89,90]. Finally, intra-articular signal changes including increased T1 signal, T2 hyperintense joint fluid, and ankylosis are highly specific findings for axSpA, and when found together with bone marrow edema can increase the positive predictive value for a diagnosis of axSpA compared with bone marrow edema alone [91,92]. Overall, it is clear that interrogation of sacroiliac joint MRI using both STIR and T1-weighted images is critical to identify both the inflammatory and structural changes of axSpA in clinical practice. MRI has long been considered inferior to CT in demonstrating the structural changes of axSpA, although evolving literature demonstrates that a specific MRI sequence, volumetric interpolated breath-hold examination (VIBE), can Inflammatory Back Pain demonstrate erosions with higher sensitivity and similar specificity compared to conventional T1-weighted imaging, and may be comparable to CT [93,94], making it a promising technique for identifying structural lesions of axSpA on MRI.