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Choosing and Interpreting Lung Function Tests for Asthma

This article provides an overview of lung function tests for asthma and offers guidance for referring physicians. Topics covered include the use of spirometry, bronchodilator testing, methacholine testing, exhaled nitric oxide, and induced sputum in the management of asthma.

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Choosing and Interpreting Lung Function Tests for Asthma

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  1. Asthma- how to choose and interpret lung function tests - a view of referring physician Matjaž Fležar MD PhD

  2. Shouldweperformspirometry at regularcheck-up visits? • 21% of general population has positive metacholine*; but only 12% have asthma • 95% of asthmatics are able to perceive acute bronchoconstriction with 20% fall in FEV1, but only 56% of all AHR positives • No long-term observational studies are done; (in one: in 3 years-time only 3% of people with AHR develop asthma*) The answer is: probably not if no proof in history Exemptions: smokers with asthma, occupational asthma, children Perception of respiratory symptoms after methacholine-induced bronchoconstriction in a general population. Devereux G, Hendrick DJ, Stenton SC. Eur Respir J. 1998 Nov;12(5):1089-93.

  3. Shouldwerepeatbronchodilatortesting? • If patient has symptomatic asthma, spirometry has to be done • If obstruction is measured (even with normal FEV1!), BD test is usefull to detect: • Refractory obstruction due to high use ob SABA • Fixed obstruction (airway remodeling)* Answer is YES, if obstruction in spirometry is present *NB. Markers of eosinophilic inflammation are important to distinguish neutrophylic asthma

  4. Should we repeat metacholine testing? • Short term (within 24 hours) repeat of the test result in tachyphilaxis • Degree of hyperresponsiveness is related to underlying inflammation • Most of population-based surveys detect non-asthmatic AHR, that vanishes over time by itself (3 year period) • Answer is: No. The treatment modifies AHR, but is not aimed at normalizing it Josephs LK, Gregg I, Mullee MA, Campbell MJ, Holgate ST. A longitudinal study of baseline FEV1 and bronchial responsiveness in patients with asthma. Eur Respir J. 1992 Jan;5(1):32-9.

  5. Highpre-test probabilityofasthmaand negative methacholine test • EVH test: positive in 75% of asthmatics (MTH in 81%) • Very rarely EVH is positive in negative MTH patients • EVH is a test of choice in detecting EIB or athletes’ airway hyperresponsiveness Roach JM, Hurwitz KM, Argyros GJ, Eliasson AH, Phillips YY. Eucapnic voluntary hyperventilation as a bronchoprovocation technique. Comparison with methacholine inhalation in asthmatics. Chest. 1994 Mar;105(3):667-72 Eliasson AH, Phillips YY, Rajagopal KR, Howard RS. Sensitivity and specificity of bronchial provocation testing. An evaluation of four techniques in exercise-induced bronchospasm Chest. 1992 Aug;102(2):347-55

  6. Shouldweperform NO andinducedsputum at regularvisits? Malerba M, Ragnoli B, Radaeli A, Tantucci C. Usefulness of exhaled nitric oxide and sputum eosinophils in the long-term control of eosinophilic asthma. Chest. 2008 Oct;134(4):733-9

  7. NO – basedtreatment Does not lead to less exacerbations Does not reduce total dose of IGK NS NS NS

  8. NO vsinducedsputum Time course of change is not the same (NO in 2 days 50% reduction; Eos in 3 months) Eos is preferable in patients with ”false” positive FENO (allergic rhinitis) The use of exhaled nitric oxide to guide asthma management: a randomized controlled trial. Shaw DE, Berry MA, Thomas M, Green RH, Brightling CE, Wardlaw AJ, Pavord ID.Am J Respir Crit Care Med. 2007 Aug 1;176(3):231-7.

  9. Shouldweperform FENO andinducedsputum at regularvisits? • FENO: • In clinically asymptomatic asthma (ACT 23-25): NO • In asthma treatment decisions: NO • In considering another diagnosis YES • In negative BD test with obstruction - YES

  10. Thank you for your patience.

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