The characteristics of the study and healthy control groups are presented in Table 1. By strictly adhering to the protocol of the study, the distribution of age and gender of subjects in both groups was similar. A significant higher proportion of asthma-rhinitis subjects had previous (45.8% vs 4.1%) and present (50.5% vs 2.7%) eczema as compared with healthy subjects. There were no differences between the two groups with regards to the percentage of subjects with a history of tuberculosis, focus of tuberculosis on chest radiography, and present and past cigarette smoking. Pulmonary function represented as FEV1 was lower in asthma-rhinitis subjects, but the difference was not statistically significant, and they also had significantly lower PD20 values (p < 0.001). Peripheral eosinophil count was significantly greater in asthma-rhinitis subjects (p < 0.001).
Thirty one subjects (14.1%) in the healthy group and 168 subjects (78.5%) in the asthma-rhinitis group had one or more positive SPT results (p < 0.0001). Positive rates of SPT to DP, DF, and B tropicalis were 14.1%, 12.3%, and 10%, respectively, in healthy control subjects, while they were 65.9% (to DP or DF) and 59.3%, respectively, in asthma-rhinitis subjects (p < 0.0001). Skin sensitization rates to other allergens were also significantly higher in asthma-rhinitis subjects than in healthy subjects.
Table 2 shows the comparison of tuberculin responses between healthy and asthma-rhinitis subjects. The distribution of tuberculin responses did not differ between the two groups (x2 = 0.01; p = 0.9). The mean tuberculin response was 7.8 mm (SE, 0.2) in healthy subjects and 8.1 mm (SE, 0.3) in asthma-rhinitis subjects (F = 0.4, p = 0.5), and it was 8.2 mm (SE, 0.2) mm in nonatopic subjects and 7.6 mm (SE, 0.3) in atopic subjects (F = 0.1, p = 0.7). The presence of BCG scar and history of BCG vaccination had no significant effect on atopy in both groups (Table 3). The rate of PPD positivity (induration > 5 mm) had no statistical difference between atopy and nonatopy in healthy and asthma-rhinitis subjects. When adding the presence of BCG scars and/or history of tuberculosis exposure (any family member or friend with tuberculosis) to PPD positivity, again no statistically significant difference was found between atopy and nonatopy in the two groups (Table 4).
In multivariate logistic regression analysis, none of the interactions were statistically significant. The OR for tuberculin reactivity a 5 mm or a 10 mm was not related to the level of serum-total IgE nor to the level of serum-specific IgE to DP and DF, skin response to DP and DF, as well as PD20 (Table 5). Again, no significant difference for coefficient of correlation was found in linear regression analysis between tuberculin skin reactivity and log serum-total IgE values as well as PD20 (Fig 1).
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Table 1—Characteristics of Healthy and Asthma-Rhinitis Subjects
|Characteristics||Healthy Subjects (n = 220)||Asthma-rhinitis Subjects (n = 214)||p Value|
|Male/female gender, No.||116/104||105/109||0.61|
|Age, yr||37.1 ± 3.5||38.0 ± 4.7||0.34|
|Previous eczema||9(4.1)||98 (45.8)||< 0.001|
|Present eczema||6(2.7)||108 (50.5)||< 0.001|
|BCG vaccination||218(99.1)||211 (98.6)||0.78|
|History of tuberculosis||3(1.4)||4(1.9)||0.47|
|Focus oftuberculosis in chest radiograph||5 (2.3)||4(1.9)||0.23|
|Present cigarette smoker||19 (8.6)||25 (11.6)||0.13|
|Past cigarette smoker||29 (13.3)||37 (17.3)||0.18|
|FEVj % of predicted||95.6 ± 9.8||87.2 ± 11.3||0.11|
|PD20, |xmol/L||10.8 ± 1.9||inCN±cr||< 0.001|
|Peripheral eosinophil count, X 106/L||104.6 ± 63.5||289.4 ± 87.2||< 0.001|
Table 2—Comparison of Tuberculin Reactivity Between Healthy and Asthma-Rhinitis Subjects
|Induration size, mm||HealthySubjects||Asthma-RhinitisSubjects||x2||p Value|
|<5||71 (32.3)||69 (32.2)||0.009||0.99|
|5-10||112 (50.9)||108 (50.5)||0.0002||0.99|
|15-20||6 (2.7)||5 (2.3)||0.07||0.79|
|> 20||2 (0.9)||3(1.4)||0.23||0.62|
Table 3—Comparison of BCG Scars Between Atopic and Nonatopic Subjects in Healthy and Asthma-Rhinitis Groups
Table 4—Distribution of Tuberculin Reactivity (> 5 mm of Induration), BCG Scars, and Tuberculosis Exposure Between Atopic and Nonatopic Subjects in Healthy, Asthma-Rhinitis Groups
|PPD a 5 mm|
|PPD a 5 mm with BCG scars|
|PPD a 5 mm with BCG scars andtuberculosisexposure|
Table 5—Logistic Regression Analysis of Relationship Between Tuberculin Skin Reactivity and Serum-Total IgE, Serum-Specific IgE to DP and DF, Skin Response to DP and DF, as Well as PD20 in All Subjects
|Variables||PPD a 5 mm||PPD a 10 mm|
|1OR||95% CI||p Value||OR||95% CI||p Value|
|Log serum-total IgE||0.771||0.308-1.934||0.581||1.071||0.505-2.276||0.859|
|Log serum-specific IgE to DP||0.362||0.031-4.183||0.432||0.536||0.051-5.586||0.602|
|Log serum-specific IgE to DF||0.620||0.208-3.026||0.471||0.427||0.126-6.182||0.774|
|SPT response to DP||0.941||0.728-1.218||0.645||0.790||0.639-1.697||0.092|
|SPT response to DF||1.200||0.728-1.218||0.086||1.227||0.836-1.452||0.081|
Figure 1. Linear regression between tuberculin skin reactivity and PD20 (top, A) and serum-total IgE (bottom,, B) from all subjects. Solid diamonds indicate healthy subjects; open squares indicate asthma-rhinitis subjects.