Criteria for Early-Phase Diffuse Idiopathic Skeletal Hyperostosis: Development and Validation

Abstract

Background Diffuse idiopathic skeletal hyperostosis (DISH) is a condition characterized by the formation of new bone along the anterolateral spinal column at four adjacent vertebral bodies. Purpose To propose and validate criteria for the early phase of DISH by using CT data from two large-scale retrospective cohorts, each with 5-year follow-up. Materials and Methods For this retrospective study, CT data at baseline and follow-up in 1367 patients (cohort I) from 2004 to 2011 were evaluated by two observers to define no DISH, early-stage DISH, and definite DISH on the basis of interval development of consecutive complete or incomplete bone bridges. An independent group of 2267 participants from the COPDGene cohort from 2008 to 2016 was used to validate the early DISH criteria (cohort II). The sensitivity and specificity of early DISH criteria were based on findings in the last CT study as the reference standard by using a nested case-control design. κ Values were calculated between seven readers and with a 3-month interval for one reader. Results Cohort I consisted of 100% men, with a mean age of 60.0 years ± 5.6 (standard deviation) and a mean time between baseline and follow-up CT of 5.0 years ± 1.1. Cohort II consisted of 51% men, with a mean age of 59.9 years ± 8.6 and a mean time between baseline and follow-up CT of 5.4 years ± 0.5. In the derivation cohort, 55 patients comprised the early DISH group. Early DISH was defined as the presence of a spinal segment with a complete bone bridge with an adjacent segment of at least a near-complete bone bridge and another adjacent segment with at least the presence of newly formed bone or when three or more adjacent segments were recorded as showing a near-complete bone bridge. In the validation cohort, sensitivity for early DISH (vs no DISH) was 96% (99 of 103 participants; 95% confidence interval [CI]: 90%, 99%). The corresponding specificity was 83% (1695 of 2034 participants; 95% CI: 82%, 85%). The Fleiss κ for interrater reliability was 0.78 (95% CI: 0.77, 0.78), and the κ for intrarater reliability was 0.89 (95% CI: 0.82, 0.96). Conclusion Early diffuse idiopathic skeletal hyperostosis (DISH) criteria had high sensitivity and specificity for predicting the development of DISH. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Block in this issue.

Trial registration: ClinicalTrials.gov NCT00608764.

Figures

Figure 1:

Patient flowchart for the presence of early diffuse idiopathic skeletal hyperostosis (DISH) in cohort I. Patients were given a diagnosis of DISH on both the first and the last noncontrast chest CT studies according to the criteria by Resnick and Niwayama (7) (new bony bridges over at least four adjacent vertebral bodies, without severe loss of intervertebral disk height and no ankylosis of the apophyseal joints). Patients without DISH at the first CT study but with DISH at the last CT study (n = 55) were regarded as having had early DISH at the first CT study. In 90 patients, DISH was present in both the first and the last CT study.

Figure 2:

Scoring system used for definition of early diffuse idiopathic skeletal hyperostosis. A score from 0 to 3 was assigned for each vertebral segment. A score of 0 indicated normal vertebral bodies without formation of new bone; a score of 1, anterior new bone formation—connected or unconnected to the vertebral body above or below (eg, nodular soft-tissue calcifications)—without a solid bony bridge (osteophytes with ≥ 2 mm distance between two bony structures) OR a connection between two adjacent vertebral bodies without abundantly formed bone; a score of 2, near-complete bridging by the anterior new bone formation with less than 2 mm of distance between the bony structures OR a full connection of the bone in a maximum of two sagittal or coronal CT sections (with a section thickness of 1 mm); and a score of 3, complete bridging between the vertebral bodies above and below the disk with abundant new bone formation in more than two sagittal or coronal CT sections (with a section thickness of 1 mm).

Figure 3:

Flowchart of the criteria for (early) diffuse idiopathic skeletal hyperostosis (DISH). The flowchart was used to differentiate between no DISH, early DISH, and definite DISH by using the criteria. The corresponding scores for the presence and completeness of a bone bridge are presented in Figure 2. For the diagnostic criteria, simply the flowchart should be used to diagnose DISH. For the classification criteria, the overall height of the intervertebral disks and the presence of ankylosis of the facet joints should be evaluated to exclude potential cases of other diseases that cause formation of new bone in the spine.

Figure 4:

Example images in patients with early diffuse idiopathic skeletal hyperostosis (DISH). A, Sagittal CT image in a 54-year-old man with early DISH with grades based on the flowchart shown in Figure 3. No complete bridge was present at any spinal segment; however, four segments were scored as showing a near-complete bone bridge (three or more segments with a score of 2). B, Sagittal CT image in a 67-year-old man with early DISH is shown. Three complete bone bridges (score of 3) were present, but not in an adjacent fashion, as is required to fulfill the criteria for DISH of Resnick and Niwayama (7). According to the flowchart in Figure 3, a complete bone bridge was present, and the highest bridge score of an adjacent segment was also a complete bone bridge (score of 3). Adjacent to these two complete bridge scores, the highest bridge score was a near-complete bone bridge (score of 2), and thus no adjacent three segments with complete bridges were present, excluding definite DISH and resulting in the diagnosis of early DISH. See also Movie 1 (online).