High resolution peripheral quantitative computed tomography (HR-pQCT) imaging allowed for highly reliable assessment of erosion in a dataset of patients with rheumatoid arthritis (RA), according to study results published as a brief commentary in the Journal of Rheumatology.
Previous studies provided evidence to support the use of HR-pQCT for the detection of periarticular bone changes. The objective of the current study was to determine the reliability of erosion measurements and to assess change over time in patients with RA.
The study included 23 patients (mean age 46 years, 60% women) with RA who underwent HR-pQCT imaging of the 2nd and 3rd digit of their dominant hand at baseline and at 12 months. Patients were selected according to the presence of bone erosions on imaging as assessed by the van der Hejde/Sharp-score, and the need to change therapy due to insufficient disease control. All of the readers participating had ≥3 years’ experience in reading HR-pQCT data sets.
The image evaluation algorithm involved assessing 8 surfaces at each metacarpophalangeal joint, specifically the palmar, dorsal, radial, and ulnar surfaces of each of the proximal phalangeal base and the metacarpal head. A total of 368 unique surfaces were evaluated at baseline and a similar number of surfaces were evaluated at 12 months to characterize cortical breaks as pathological (erosions) or physiological, and to quantify erosion width and depth.
Interclass correlation coefficients, calculated as an indicator of variability in cortical break depth and width measurements between all 4 readers was used to assess reliability along with percentage of agreement and Light’s kappa for the chance corrected agreement.
The percentage agreement for evaluability of all the images between all readers was 80% (589/736). The percentage of agreement for the presence of cortical break on 585 images deemed to be evaluable by all 4 readers was 57% (334/585).
A total of 99 cortical breaks were identified on images at baseline and follow-up, with a percentage of agreement for classifying a cortical break as pathological or physiological between all readers of 81% (80/99).
Interclass correlation coefficients for the mean measurements of width and depth of the pathological breaks ranged between 0.819-0.883, and 0.771-0.907, respectively. Most physiological cortical breaks were found at the palmar phalangeal bases (31 physiological breaks), whereas most erosions were located at the radial metacarpal heads (25 pathological breaks).
Between baseline and follow-up there was a significant increase in mean numbers of erosions (0.73 vs. 1.02; P =.0001), axial (1.31 vs. 1.79; P =.0001) or perpendicular (1.07 vs. 1.69; P =.0001) width, and axial (0.87 vs. 1.25, P =.0001) and perpendicular width (0.88 vs. 1.07; P =.001) depth.
The researchers noted that limiting the in-depth analysis to images that were determined by all readers to be sufficient and with evidence for a cortical reduced the number of analyzable surfaces. They emphasized the need for adequate training of readers before interpreting HR-pQCT images.
“HR-pQCT evaluation using trained readers allows for highly reliable and precise detection of cortical breaks and facilitates differentiation of pathological from physiological cortical breaks,” concluded the researchers.
Finzel S, Manske SL, Barnabe C, et al. Reliability and change in erosion measurements by high-resolution peripheral quantitative computed tomography in a longitudinal dataset of rheumatoid arthritis patients . J Rheumatol. Published online Sep 15, 2020. doi:10.3899/jrheum.191391