MRI superior to radiograph in evaluating children for sacroiliitis
MRI interrater reliability is superior to that of radiographs — which demonstrated a significant proportion of both false negative and false positive findings — for global sacroiliitis impression among juvenile patients, according to findings published in Arthritis Research & Therapy.
“This study is important because insurance companies are often insistent that we — rheumatologists — order a radiograph before an MRI when we are evaluating for sacroiliitis in children,” Pamela F. Weiss, MD, MSCE, of the Children’s Hospital of Philadelphia, told Healio Rheumatology. “Given the relatively short duration of symptoms in most children, and the rarity of bony lesions detectable by radiographs, MRI may be more informative and save the child unnecessary radiation exposure.”
To compare the diagnostic utility of radiographs to MRI in the evaluation of juvenile patients with suspected sacroiliitis, the researchers conducted a retrospective cross-sectional study of all children at the Children’s Hospital of Philadelphia with suspected or confirmed spondyloarthritis, who underwent both forms of imaging no more than 6 months apart. This included 228 children aged 6 to 18 years between January 2012 and May 2016. From these children, 60 pairs of images met the researchers’ inclusion criteria.
Each image was scored by five raters, with interrater reliability determined using Fleiss’s kappa coefficient (). In addition, the researchers calculated the test properties of radiographs for the imaging of sacroiliitis using MRI global sacroiliitis impression as the reference standard.
According to the researchers, the interrater agreement for global sacroiliitis impression was = 0.34 (95% CI, 0.19-0.52) for radiographs and = 0.72 (95%, CI 0.52-0.86) for MRI. The sensitivity of radiographs across raters ranged from 25% to 77.8%, and their specificity ranged from 60.8% to 92.2%. In addition, positive predictive values ranged from 25.9% to 52%, and negative predictive values ranged from 82.7% to 93.9%.
The researchers also found that the misclassification rate for negative radiographs/positive MRI scans ranged from 6% to 17%. For positive radiographs/negative MRI scans, the range was 48% to 74%. In addition, when the reference standard was changed to structural lesions consistent with sacroiliitis on MRI, the misclassification rate for negative radiographs/positive MRI scans was higher, and positive radiographs/negative MRI scans marginally improved.
“Interrater reliability of MRI was superior to radiographs for global sacroiliitis impression,” Weiss said. “Misclassification for both negative and positive radiographs was high across raters. Radiographs have limited utility in screening for sacroiliitis in children and result in a significant proportion of both false negative and positive findings versus MRI findings. We hope that this gives our colleagues something to not only think about for their own clinical practice but also to reference during conversations with insurance companies when discussing the appropriate imaging evaluation of these children.” – by Jason Laday
Disclosure: Weiss reports support from the Rheumatology Research Foundation. Please see the study for all other authors’ relevant financial disclosures.