Nationwide epidemiological survey of patients with idiopathic interstitial pneumonias using clinical personal records]

A nationwide epidemiological survey of idiopathic interstitial pneumonias (IIPs) in 2005 was performed using clinical personal records. According to the data from the Japan Intractable Diseases Information Center, 4,396 patients with IIPs were covered by public insurance. The prevalence of IIPs in Japan was estimated to be 3.44 per 100,000. The forms of 1543 patients (new: 658, recurrent: 885) were collected. Of 1543 cases, 1322 cases (85.7%) had idiopathic pulmonary fibrosis (IPF), therefore details were investigated in patients with IPF. The mean age at onset was 65.4 years and men were more frequent than women (878 in men, 444 in women). The severity, diagnostic method, symptoms, imaging findings, and pulmonary function tests were analyzed in the new forms. Severity levels of I, II, III and IV were seen in 32, 28, 177, and 287 cases, respectively. A pathological diagnosis was made in 67 cases (12%). The positive rates of fine crackles, dry cough, exertional dyspnea, and finger clubbing were 98%, 94%, 98%, and 53%, respectively. On HRCT, honeycomb was noted in the subpleural lung lesions in more than 90% of the cases. As for pulmonary function tests, restrictive and diffusing capacity impairment were noted in 86% and 92%, respectively, and SpO2 was below than 90% in 91% on a 6-minute walking test. The serum KL-6 level was elevated in 95%. Most of the IPF analyzed cases were at a severity level of III or IV because the analysis aimed at those coverage by public insurance. Since this was only the initial nationwide epidemiological survey in Japan, the current situation should be investigated.