Positive predictive value of the International Classification of Diseases, 10th revision, codes to identify osteonecrosis of the jaw in patients with cancer.

BACKGROUND

Osteonecrosis of the jaw (ONJ) is an important adverse event associated with therapies suppressing bone turnover, especially in patients with high-dose regimens of antiresorptive therapy, such as cancer patients. Danish health registries are an important resource for monitoring side effects of drugs. The International Classification of Diseases, 10th revision (ICD-10), currently used in Denmark, does not have a specific code for ONJ, making it difficult to monitor its occurrence.

OBJECTIVES

To estimate the positive predictive value (PPV) for ONJ of currently used ICD-10 codes, suggested by Danish oral and maxillofacial surgeons, in order to assess feasibility of identification of ONJ cases among cancer patients in the Danish National Registry of Patients (DNRP).

METHODS

This study was conducted in northern Denmark (1.8 million inhabitants) among patients with a history of cancer. In Denmark ONJ cases are referred to hospital-based departments of oral and maxillofacial surgery (DOMS). In the DNRP, we identified patients with potential ONJ diagnosed at DOMS (as suggested by a series of ICD-10 codes) from 1 January 2005 to 31 December 2009. To confirm or rule out ONJ, we reviewed hospital records of these patients originating from DOMS. A confirmed ONJ case was defined by the presence of exposed maxillofacial bone for 8 weeks or more, in the absence of previous craniofacial radiation therapy. The PPV was the proportion of confirmed cases among all potential cases.

RESULTS

Among 85,910 eligible cancer patients, we identified 91 (0.11%) potential cases of ONJ, of which 18 were confirmed. The overall PPV was 20% (95% CI: 12-29%), ranging from 0% to50% for individual ICD-10 codes.

CONCLUSIONS

A majority of cases identified by the suggested ICD-10 codes did not fulfill the criteria for ONJ, even though the potential cases were identified at DOMS. Therefore, reliance on ICD-10 codes, without hospital chart review, will lead to an overestimation of the occurrence of ONJ among cancer patients.