The PC*, is then determined by logarithmic or linear interpolation between these 2 points. The interpolation may be performed using an algebraic formula or by manually graphing the log dose or dose versus response. These various methods of calculating PC*, have been compared. The differences between PC*, calculated logarithmically or linearly were small (0% to 6%; mean: 3.7% ±2.1% [SD]), much smaller than the observed difference on repeated PC*, testing. Manual graphing for interpolating PCjo produced greater error than the use of algebraic formulas. The authors of the study suggested that for simplicity and accuracy, formulas should be used for either linear or logarithmic interpolation.
The measurement of nonspecific bronchial hyperresponsiveness is of potential importance in the epidemiologic investigation of populations exposed to dust and fumes as well as to known pulmonary sensitizers. It is important that the techniques of measurement be standardized and be rapid and simple to administer, avoiding bulky or expensive equipment. Of the 3 methods discussed, the Yan method, although not at present widely adopted in clinical and research work, appears to fulfill all of the scientific and practical requirements demanded.