Up to a quarter of patients with osteonecrosis of the jaw associated with antiresorptive agents remain undiagnosed.

Recent data suggest that the traditional definition of bisphosphonate-associated osteonecrosis of the jaw (ONJ) may exclude patients who present with the non-exposed variant of the condition. To test the hypothesis that a proportion of patients with ONJ remain undiagnosed because their symptoms do not conform to the traditional case definition, we did a secondary analysis of data from MISSION (Multicentre study on phenotype, definition and classification of osteonecrosis of the jaws associated with bisphosphonates), a cross-sectional study of a large population of patients with bisphosphonate-associated ONJ who were recruited in 13 European centres. Patients with exposed and non-exposed ONJ were included. The main aim was to quantify the proportion of those who, according to the traditional case definition, would not be diagnosed with ONJ because they had no exposed necrotic bone. Data analysis included descriptive statistics, median regression, and Fisher's exact test. A total of 886 consecutive patients were recruited and 799 were studied after data cleaning (removal or correction of inaccurate data). Of these, 607 (76%) were diagnosed according to the traditional definition. Diagnosis in the remaining 192 (24%) could not be adjudicated, as they had several abnormal features relating to the jaws but no visible necrotic bone. The groups were similar for most of the phenotypic variables tested. To our knowledge this is the first study in a large population that shows that use of the traditional definition may result in one quarter of patients remaining undiagnosed. Those not considered to have ONJ had the non-exposed variant. These findings show the importance of adding this description to the traditional case definition.