Value of a negative aeroallergen skin-prick test result in the diagnosis of asthma in young adults: Correlative study with methacholine challenge testing

Yael Graif, Mordechai Yigla, Naveh Tov, Mordechai R. Kramer

Research output: Contribution to journalArticlepeer-review

Abstract

Background: None of the existing tests for the diagnosis of asthma are considered to be definitive. Certain circumstances require prompt diagnosis, and a test able to predict the absence of asthma would be very useful. Objective: To evaluate the contribution of a skin-prick test (SPT) to the diagnostic workup of subjects with suspected asthma. Patients and methods: The study included three groups of subjects aged 18 to 24 years: group A, asthmatic patients (n = 175); group B, control subjects (n = 100); and group C, subjects with suspected asthma (n = 150) with normal spirometry findings and a negative exercise challenge test result. All underwent an SPT to a battery of common aeroallergens, and group C underwent a methacholine challenge test (MCT) in addition. The sensitivity, specificity, positive predictive value, and negative predictive values (NPV) of the SPT were calculated using provocative concentrations of methacholine causing a 20% fall in FEV1 (PC20) of < 4 mg/mL and < 8 mg/mL as diagnostic cutoff values for asthma in the MCT. Bayes' formula was used to determine posttest probabilities of having asthma, both for positive and negative SPT results. Results: A positive SPT result to at least one allergen was found in 95.5%, 54%, and 69% of patients in the three groups, respectively. The sensitivity, specificity, and NPV of the SPT were 90.7%, 52.0%, and 84.8%, respectively, with a cutoff value of PC20 < 8 mg/mL. The lower cutoff, PC20 < 4 mg/mL, increased the sensitivity and NPV to 98.2% and 97.8%, respectively. A negative SPT result decreased the probability of having asthma by 10-fold to 20-fold in subjects whose pretest probability was low to moderate. Conclusions: Incorporating an SPT into the workup of subjects with suspected asthma can reduce the cost of this process significantly. The SPT may be used as a simple, fast, safe, inexpensive, and reliable method to predict the absence of asthma in young adults.

Original languageEnglish
Pages (from-to)821-825
Number of pages5
JournalChest
Volume122
Issue number3
DOIs
StatePublished - Sep 2002
Externally publishedYes

Keywords

  • Bronchial asthma
  • Bronchial hyperresponsiveness
  • Skin-prick test

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