Selection of effective maximal expiratory parameters to differentiate asthmatic patients from healthy adults by discriminant analysis using all possible selection procedure.

Maximal expiratory volume-time and flow-volume (MEVT and MEFV) curves were drawn for young male nonsmoking healthy adults and for young male nonsmoking asthmatic patients. Eleven parameters, two MEVT (%FVC and FEV1.0%), six MEFV (PFR, V75, V50, V25, V10 and V50/V25), and three MTC parameters (MTC75-50, MTC50-25 and MTC25-RV) were used for the multivariate analysis. The multivariate analysis in this study consisted of correlation coefficient matrix computation, the test for mean values in the multivariates, and the linear discriminant analysis using the all possible selection procedure (APSP). Correlation coefficients among flow rate parameters and flow rate related parameters in high lung volumes were different between the two groups. In the eleven-parameter discriminant analysis by APSP using single parameters, PFR, V75 (flow rate at 75% of forced vital capacity), and FEV1.0% were considered to be the effective parameters. In the seven-parameter discriminant analysis using the parameter groups, the group of all parameters and the %FVC and flow rate-related parameter group were considered to be the effective numerical alternatives to MEFV curves discriminating between healthy adults and asthmatic patients.