National differences in reporting 'pneumonia' and 'pneumonia interstitial': an analysis of the WHO International Drug Monitoring Database on 15 drugs in nine countries for seven pulmonary conditions.

Purpose: Increased post-marketing reports of 'interstitial pneumonia' as an adverse drug reaction (ADR) from the use of gefitinib, irinotecan, or leflunomide among patients in Japan have not been noted in other countries. The WHO International Drug Monitoring Database was analyzed to examine Japan's pattern of reporting the term 'pneumonia interstitial' for 15 selected drugs with a mixed history of association with pulmonary ADRs.

Methods: ADR counts from the WHO Database for 1992-2001 were obtained for 15 disparate drugs (three androgen blockers, eight cytotoxics, one proton pump inhibitor, one monoclonal antibody, and two anti-epileptics) from nine countries (Australia, France, Germany, Italy, Japan, Spain, Thailand, U.K., and U.S.A.) for seven pulmonary ADR terms (alveolitis fibrosing, pneumonia, pulmonary fibrosis, lung fibrosis interstitial, pulmonary infiltration, interstitial lung disease, and pneumonia interstitial). Statistical analyses included estimating Poisson-distributed expected rates, observed/expected (O/E) ratios, and 95% confidence intervals (CI). The overlapping nature and changes in definition over time of these terms in medical texts and in the WHO-ART, COSTART, J-ART, and MedDRA coding systems is also noted.

Results: Compared to other countries, both Japan and France did not have higher O/E reporting ratios for all seven pulmonary ADRs combined, but did have higher O/E ratios for 'pneumonia interstitial' and lower O/E ratios for 'pneumonia' for the same drugs.

Conclusions: Japan and France were found to preferentially use the term 'pneumonia interstitial' for ADR where other countries used 'pneumonia.' This cultural pattern coincides with the fact that 'pneumonia interstitial' in older versions of COSTART, J-ART, and MedDRA were subsumed under infectious pulmonary diseases.