Diagnosis of diffuse idiopathic skeletal hyperostosis with chest computed tomography: inter-observer agreement.

OBJECTIVE: To evaluate and improve the interobserver agreement for the CT-based diagnosis of diffuse idiopathic skeletal hyperostosis (DISH).

METHODS: Six hundred participants of the CT arm of a lung cancer screening trial were randomly divided into two groups. The first 300 CTs were scored by five observers for the presence of DISH based on the original Resnick criteria for radiographs. After analysis of the data a consensus meeting was organised and the criteria were slightly modified regarding the definition of 'contiguous', the definition of 'flowing ossifications' and the viewing plane and window level. Subsequently, the second set of 300 CTs was scored by the same observers. κ ≥ 0.61 was considered good agreement.

RESULTS: The 600 male participants were on average 63.5 (SD 5.3) years old and had smoked on average 38.0 pack-years. In the first round κ values ranged from 0.32 to 0.74 and 7 out of 10 values were below 0.61. After the consensus meeting the interobserver agreement ranged from 0.51 to 0.86 and 3 out of 10 values were below 0.61. The agreement improved significantly.

CONCLUSIONS: This is the first study that reports interobserver agreement for the diagnosis of DISH on chest CT, showing mostly good agreement for modified Resnick criteria.

KEY POINTS: • DISH is diagnosed on fluoroscopic and radiographic examinations using Resnick criteria • Evaluation of DISH on chest CT was modestly reproducible with the Resnick criteria • A consensus meeting and Resnick criteria modification improved inter-rater reliability for DISH • Reproducible CT criteria for DISH aids research into this poorly understood entity.