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Table 1 The representativeness of the clinically examined sample based on the questionnaire study data*

From: Sensitization to airborne allergens among adults and its impact on allergic symptoms: a population survey in northern Vietnam

Symptoms or conditions

The entire cohort

Invited to clinical examinations

Participants in clinical examinations

Participants in skin prick test

Difference (p-value)**

n = 5,782

n = 1,500

n = 684

n = 533

Ever asthma

4.5

4.3

4.1

3.8

0.467

Physician diagnosed asthma

3.9

3.3

3.2

3.0

0.581

Asthma medicine

2.1

1.9

1.6

1.1

0.121

Allergic rhinitis

17.2

20.7

19.2

16.8

0.013

Recurrent wheeze

3.7

3.4

3.7

3.2

0.579

Wheezing without a cold

3.2

2.8

3.4

3.2

0.396

Attack of SOB

5.2

4.9

5.8

4.7

0.433

Dyspnea

3.5

3.6

3.9

4.0

0.458

  1. *Prevalence (%) of symptoms and conditions in the entire cohort, among those invited to the clinical examinations, and those who participated in the clinical examinations.
  2. **Difference between participants in skin prick testing and non-participants in ages ≤60 years old.