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

Recent datasuggestthatthetraditionaldefinitionofbisphosphonate-associatedosteonecrosisofthejaw(ONJ)mayexcludepatientswho present withthenon-exposedvariantofthecondition.TotestthehypothesisthataproportionofpatientswithONJremainundiagnosed because theirsymptomsdonotconformtothetraditionalcasedefinition,wedidasecondaryanalysisofdatafromMISSION(Multicentre study onphenotype,definitionandclassificationofosteonecrosisofthejawsassociatedwithbisphosphonates),across-sectionalstudyof a largepopulationofpatientswithbisphosphonate-associatedONJwhowererecruitedin13Europeancentres.Patientswithexposedand non-exposedONJwereincluded.Themainaimwastoquantifytheproportionofthosewho,accordingtothetraditionalcasedefinition, wouldnotbediagnosedwithONJbecausetheyhadnoexposednecroticbone.Dataanalysisincludeddescriptivestatistics,medianregression, and Fisher’sexacttest.Atotalof886consecutivepatientswererecruitedand799werestudiedafterdatacleaning(removalorcorrectionof inaccurate data).Ofthese,607(76%)werediagnosedaccordingtothetraditionaldefinition.Diagnosisintheremaining192(24%)couldnot be adjudicated,astheyhadseveralabnormalfeaturesrelatingtothejawsbutnovisiblenecroticbone.Thegroupsweresimilarformostof the phenotypicvariablestested.Toourknowledgethisisthefirststudyinalargepopulationthatshowsthatuseofthetraditionaldefinition may resultinonequarterofpatientsremainingundiagnosed.ThosenotconsideredtohaveONJhadthenon-exposedvariant.Thesefindings showtheimportanceofaddingthisdescriptiontothetraditionalcasedefinition.