Determinants of Percent Predicted FEVi in Current Asthmatic Subjects: Data

Current dyspnea (American Thoracic Society scale) was an additional significant factor relating to the level of %FEV[. Current physician-diagnosed chronic bronchitis also was a significant predictor of %FEV|; with this diagnosis present in 20.7 percent of these current asthmatic subjects. Variables that did not reach the 0.05 level of significance for inclusion after controlling for WS-AG included gender, pack-years of smoking, smoking status, reported age of onset of asthma, reported duration of asthma, eosinophil count, Z-scored IgE, positive vs negative allergy skin test, amount of positive skin test reactivity, cough or phlegm or both.
To simplify presentation of the data, the WS-AG values were reduced to three grades; grade 1: WS • AG values 1 through 4 (n = 133); grade 2: WS-AG values 5 through 9 (n=84); and grade 3: WS-AG values 10 through 15 (n=44). Figure 2 shows %FEVi by gender by WS-AG grade. Although the relationship of WS-AG to %FEVi was present in both sexes and the gender difference widened with increasing WS-AG, the gender differences were not significant overall nor within individual WS • AG grades. Figure 3 shows %FEV] by smoking status by WS-AG. Unlike gender differences, the differences by smoking are not consistent between WS • AG categories.

Overall smoking status is not significantly related to %FEVi, nor is it significant within individual WS-AG grades. Figure 4 shows %FEV! by physician-diagnosed chronic bronchitis by WS-AG. Overall differences are significant (p<0.0001), as are those with WS-AG grade 1 (p<0.01) and with WS • AG grade 3 (p<0.05). asthma inhalers

Table 1 shows the mean and standard deviations for %FEV], percent predicted forced vital capacity (%FVC), the FEVi/FVC ratio, the percent predicted rate of flow at 50 percent of the FVC (%V50), the percent predicted rate of flow at 75 percent of the FVC (%V75), and the percent predicted expiratory flow between 25 and 75 percent of the FVC (%FEF) by the three grades of WS • AG. All are significant by analysis of variance.

Figure-2

Figure 2. The %FEVj by sex and WS-AG interaction. Overall gender differences are not significant, nor are differences in individual interaction grades. See text for WS-AG interaction definition.

Figure-3

Figure 3. The %FEVj by smoking status and WS-AG interaction. Overall differences in smoking status are not significant, nor are differences in individual interaction grades. See text for WS AG interaction definition.

Figure-4

Figure 4. The %FEVi by current chronic bronchitis and WS-AG interaction. Overall differences are significant (p<0.0001), as are those with grade 1 (p<0.01) and with grade 3 (p<0.05). See text for WS-AG interaction.

Table 1—Spirometric Values hy Wheeze Scale Age Group Grade

Grade 1 Grade 2 Grade 3 Probability
%FEVi 93.1 ±16.3 81.7 ±17.7 63.8±21.6 <0.0001
%FVC 99.0 ± 18.1 90.2 ±17.6 77.7 ±18.2 <0.0001
FEVi/FVC 80.1 ±8.0 75.3 ±9.7 65.9 ±14.6 <0.0001
%V50 80.3 ±25.0 65.1 ±26.5 45.0 ±28.7 <0.0001
%V75 78.4 ±32.3 64.2 ±33.6 53.5 ±37.2 <0.0001
Percent predicted expiratory flow between 25 and 75% of FVC 80.3 ±25.3 65.8 ±26.6 48.0 ±30.0 <0.0001

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