| Questionnaire only (model 1) | Questionnaire + SPT (model 2) | Questionnaire + BR (model 3) | Questionnaire + SPT + BR (model 4) | |||||
| β | OR (95% CI) | β | OR (95% CI) | β | OR (95% CI) | β | OR (95% CI) | |
| Intercept | −2.86 | −3.16 | −3.44 | −3.55 | ||||
| Symptoms indicative for asthma | 0.70 | 2.2 (1.1 to 4.3) | 0.62 | 1.9 (1.0 to 3.9) | 0.61 | 1.9 (1.0 to 3.8) | 0.50 | 1.7 (0.8 to 3.5) |
| Allergic symptoms | 1.38 | 4.6 (2.2 to 9.5) | 1.10 | 3.2 (1.5 to 7.0) | 1.39 | 4.3 (2.1 to 9.1) | 1.07 | 3.1 (1.4 to 6.9) |
| Positive SPT to common allergens | – | – | 0.99 | 2.8 (1.4 to 5.8) | – | – | 0.84 | 2.4 (1.2 to 5.1) |
| Measurable PC20 (⩽32 mg/ml) | – | – | – | – | 1.32 | 4.0 (2.0 to 7.8) | 1.21 | 3.6 (1.8 to 7.2) |
| ROC area (95% CI) after bootstrapping | 0.731 (0.663 to 0.799) | 0.754 (0.682 to 0.826) | 0.777 (0.710 to 0.844) | 0.785 (0.717 to 0.853) | ||||
| Hosmer-Lemeshow test (p value) | 0.999 | 0.985 | 0.991 | 0.991 | ||||
ROC area SPT to common allergen 0.69 (95% CI 0.61 to 0.77).
ROC area measurable PC20 0.69 (95% CI 0.60 to 0.77).
From the questionnaire model, the individual probability of developing LA sensitisation can be estimated using the following formula:
P(sensitisation) = 1/(1+ exp(−(−2.86 + symptoms indicative for asthma × 0.70 + allergic symptoms × 1.38))).
Predictor is valued as 1 when present and 0 when absent.
β, regression coefficient after multiplication by correction factor from bootstrapping procedure; BR, bronchial responsiveness to methacholine; 95% CI, 95% confidence interval; OR, odds ratio; ROC, receiver operating characteristic; SPT, skin-prick testing.