Pulmonary thromboembolism (PTE) is considered an uncommon disease in Japan
and there are not any reported prospective studies on the incidence of PTE
in Japan. The objective of the present study was to determine the number of
patients with PTE per year in a prospective study using a questionnaire. L
etters were sent to clinical departments in university schools of medicine
or medical colleges, and to hospitals with more than 100 beds. The diagnosi
s of PTE was to be confirmed by (1) pulmonary artery stenosis or occlusion
on pulmonary angiography, (2) mismatch of pulmonary perfusion scintigraphy
and pulmonary ventilation scintigraphy, (3) changes on pulmonary perfusion
scintigraphy performed twice, or (4) autopsy. The questionnaire elicited 2,
341 replies (the withdrawal rate was 40.7%). In 231 hospitals, 237 patients
were diagnosed definitely during the study period of 2 months from 1 Augus
t to 30 September 1996. From this it was estimated that there are 3,492 (95
% confidence interval: 3,280-3,703) patients with PTE per year, which impli
es that the incidence is 28 persons per 1,000,000 people per year, confirmi
ng that PTE is rare in Japan.