[A study of hyperreactivity test thresholds over the last 9 years in asthmatics]

We have regularly performed acetylcholine hyperreactivity tests (Ach-HRT) on asthmatics on their first visit to our allergy clinic, and gained the impression that Ach-HRT thresholds have risen over the last nine years. We studied the thresholds in four different years: 1983, '85, '87 and '91 in 578 male cases and 680 female cases. Our findings were as follows. 1) The Ach-HRT threshold increased in the last 9 years, especially in the asthmatic group aged from 20 to 59 years old. 2) We studied the factors which might affect Ach-HRT in this age group. No significant difference were seen in the percent of peripheral blood eosinophil count and in clinical severities. The mean percent of baseline FEV1.0 was high in '91 and low in '83. We studied the Ach-HRT threshold in case with good pulmonary function whose %FEV1.0 was over 90% and found that the Ach-HRT threshold was high in '91 and low in '83. 3) The number of extrinsic cases increased gradually in number over the 9 years, and a high Ach-HRT threshold was clearer in the extrinsic cases. We concluded that the mean Ach-HRT threshold of our patients was rising especially in the extrinsic cases.