Absence of Relationships Between Tuberculin Responses and Development of Adult Asthma Outcomes

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.

Tuberculin Injections

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).

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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
10-15 29(13.2) 29 (13.5) 0.16 0.70
15-20 6 (2.7) 5 (2.3) 0.07 0.79
> 20 2 (0.9) 3(1.4) 0.23 0.62
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Table 3—Comparison of BCG Scars Between Atopic and Nonatopic Subjects in Healthy and Asthma-Rhinitis Groups

Variables Healthy Asthma-Rhinitis
1Nonatopic Atopic INonatopic Atopic
Total population 189 31 46 168
BCG scars
Yes 168 25 38 138
No 21 6 8 30
x2 1.68 0.05
p Value 0.19 0.99

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

Variables Healthy Asthma-Rhinitis
Nonatopic Atopic iNonatopic Atopic
Total population 189 31 46 168
PPD a 5 mm
Yes 130 21 30 115
No 59 10 16 53
x2 0.01 0.17
p Value 0.87 0.73
PPD a 5 mm with BCG scars
Yes 78 14 16 62
No 52 7 14 53
x2 0.34 0.27
p Value 0.60 0.63
PPD a 5 mm with BCG scars andtuberculosisexposure
Yes 32 8 4 22
No 46 6 12 40
x2 1.25 0.62
p Value 0.25 0.45

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
PD20 1.211 0.954-1.536 0.105 0.890 0.735-1.078 0.234

 

Linear Regression

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.

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