Evaluation of an algorithm ascertaining cases of osteonecrosis of the jaw in the Swedish National Patient Register

BACKGROUND Osteonecrosis of the jaw (ONJ) is a medical condition associated with antiresorptive drugs, among others, used to treat osteoporosis and bone metastasis. Currently, there is no consensus regarding the definition of ONJ, and no ONJ-specific International Classification of Diseases-10 code exists. Therefore, register-based studies of this condition may be troublesome. PURPOSE To evaluate an algorithm ascertaining ONJ cases in an attempt to facilitate future assessments of ONJ in clinical and epidemiological studies. METHODS By means of the Patient Register and the Prescribed Drug Register, we identified all postmenopausal female residents in Sweden from 2005 through 2009. To identify potential cases of ONJ, we employed an algorithm including the following conditions: periapical abscess with sinus, inflammatory conditions of jaws, alveolitis of jaws, idiopathic aseptic necrosis of bone, osteonecrosis due to drugs, osteonecrosis due to previous trauma, other secondary osteonecrosis, other osteonecrosis, and unspecified osteonecrosis. Women seen at departments of oral and maxillofacial surgery, with at least one of the conditions, were classified as potential cases of ONJ. Conditions in anatomic sites other than the jaw were excluded. Validation was performed through medical record review. Case confirmation was based on the ONJ definition by the American Association of Oral and Maxillofacial Surgeons. The algorithm was evaluated by positive predictive values (PPVs) stratified by diagnosis. RESULTS For the 87 potential cases identified through our algorithm, the medical records were obtained for 83. The overall PPV was 18% (95% confidence interval (CI) 10%-28%). The highest PPV was observed in osteonecrosis due to drugs (83%, 95% CI 36%-100%). Several diagnoses had a PPV of 0 or were not used at all (periapical abscess with sinus, alveolitis of jaws, idiopathic aseptic necrosis of bone, osteonecrosis due to previous trauma, other secondary osteonecrosis, other osteonecrosis, and unspecified osteonecrosis). CONCLUSION It was possible to ascertain cases of ONJ from the Swedish registers using this algorithm; however, the PPV was low. Thus, further refinements of the algorithm are necessary.