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Marques, M.L.; Silva, N.P. da; Heijde, D. van der; Reijnierse, M.; Baraliakos, X.; Braun, J.; ... ; Ramiro, S. (2022)

Hounsfield units measured in low dose CT reliably assess vertebral trabecular bone density changes over two years in axial spondyloarthritis

Article / Letter to editor
Objectives: To describe low dose Computed Tomography (ldCT) Hounsfield Units (HU) two-year change-from -baseline values (expressing trabecular bone density changes) and analyse their inter-reader reliability per vertebra in radiographic axial spondyloarthritis (r-axSpA). Methods: We used 49 patients with r-axSpA from the multicentre two-year Sensitive Imaging in Ankylosing Spondylitis (SIAS) study. LdCT HU were independently measured by two trained readers at baseline and two years. Mean (standard deviation, SD) for the change-from-baseline HU values were provided per vertebra by reader. Intraclass correlation coefficients (ICC; absolute agreement, two-way random effect), Bland-Altman plots and smallest detectable change (SDC) were obtained. Percentages of vertebrae in which readers agreed on the direction of change and on change >|SDC| were computed. Results: Overall, 1,053 (98% of all possible) vertebrae were assessed by each reader both at baseline and two years. Over two...Show moreObjectives: To describe low dose Computed Tomography (ldCT) Hounsfield Units (HU) two-year change-from -baseline values (expressing trabecular bone density changes) and analyse their inter-reader reliability per vertebra in radiographic axial spondyloarthritis (r-axSpA). Methods: We used 49 patients with r-axSpA from the multicentre two-year Sensitive Imaging in Ankylosing Spondylitis (SIAS) study. LdCT HU were independently measured by two trained readers at baseline and two years. Mean (standard deviation, SD) for the change-from-baseline HU values were provided per vertebra by reader. Intraclass correlation coefficients (ICC; absolute agreement, two-way random effect), Bland-Altman plots and smallest detectable change (SDC) were obtained. Percentages of vertebrae in which readers agreed on the direction of change and on change >|SDC| were computed. Results: Overall, 1,053 (98% of all possible) vertebrae were assessed by each reader both at baseline and two years. Over two years, HU mean change values varied from-23 to 28 and 29 for reader 1 and 2, respectively. Inter-reader reliability of the two-year change-from-baseline values per vertebra was excellent: ICC:0.91-0.99; SDC:6-10; Bland-Altman plots were homoscedastic, with negligible systematic error between readers. Readers agreed on the direction of change in 88-96% and on change >|SDC| in 58-94% of vertebrae, per vertebral level, from C3 to L5. Overall, similar results were obtained across all vertebrae. Conclusion: LdCT measurement of HU is a reliable method to assess two-year changes in trabecular bone density at each vertebra from C3-L5. Being reliable across all vertebrae, this methodology can aid the study of trabecular bone density changes over time in r-axSpA, a disease affecting the whole spine.Show less
Axial spondyloarthritis
Hounsfield units
Low dose CT
Reliability
All authors
Marques, M.L.; Silva, N.P. da; Heijde, D. van der; Reijnierse, M.; Baraliakos, X.; Braun, J.; Gaalen, F. van; Ramiro, S.
Date
2022-12-13
Journal
Seminars in Arthritis and Rheumatism
Volume
58
DOI
doi:10.1016/j.semarthrit.2022.152144