Does the methacholine test reproduce symptoms?
- PMID: 21037997
- PMCID: PMC2975503
- DOI: 10.1155/2010/908147
Does the methacholine test reproduce symptoms?
Abstract
Background: The interpretation of methacholine test results do not usually consider the symptoms for which the subject was referred and those that occur during the test.
Objective: To assess the association between methacholine test results and symptoms, and to examine variables that may affect this association. METHODS A total of 400 prospectively chosen subjects who underwent methacholine testing for possible asthma were investigated. The subjects answered a short questionnaire regarding the symptoms for which they had been referred and those that were encountered during the methacholine test.
Results: The positive predictive value for the reproduction of symptoms during the test compared with symptoms for which subjects had been referred were 84% for dyspnea, 87% for cough, 81% for wheezing and 72% for chest tightness. The positive predictive value among the values obtained by measuring the provocative concentration of methacholine causing a 20% fall (PC20) in forced expiratory volume in 1 s on the one hand, and specific symptoms on the other, varied by up to approximately 50%; negative predictive values were higher. Forty-eight per cent of subjects with a PC20 of 16 mg⁄mL or lower reported that the test had globally reproduced their symptoms. This association was significantly stronger in women, young subjects and those taking inhaled steroids.
Conclusions: The methacholine test generally reproduced the symptoms for which the subjects were referred. The absence of a specific symptom (eg, dyspnea, cough, wheezing or chest tightness), either in daily life or at the time of methacholine testing, was more generally associated with a negative test than the reverse. The global impression that the test had reproduced what the patient had experienced in daily life was significantly associated with a positive test (ie, a PC20 of 16 mg⁄mL or lower), with the association being stronger in young subjects and women.
HISTORIQUE :: En général, l’interprétation des résultats du test à la méthacholine ne tient pas compte des symptômes pour lesquels le sujet a été aiguillé et ceux qui se produisent pendant le test.
OBJECTIF :: Évaluer l’association entre les résultats du test à la méthacholine et les symptômes et examiner les variables susceptibles d’influer sur cette association.
MÉTHODOLOGIE :: Au total, 400 sujets sélectionnés de manière prospective qui ont subi un test à la méthacholine en raison d’un asthme possible ont fait l’objet d’une évaluation. Les sujets ont répondu à un court questionnaire au sujet des symptômes pour lesquels ils ont été aiguillés et de ceux qui ont été observés pendant le test à la méthacholine.
RÉSULTATS :: La valeur prédictive positive de la reproduction des symptômes pendant le test par rapport aux symptômes pour lesquels les sujets avaient été aiguillés était la dyspnée dans 84 % des cas, la toux dans 87 % des cas, la respiration sifflante dans 81 % des cas et l’oppression dans 72 % des cas. La valeur prédictive positive parmi les valeurs obtenues en mesurant la concentration provocatrice de méthacholine entraînant une chute de 20 % (CP20) du volume expiratoire maximal par seconde d’une part, et des symptômes spécifiques d’autre part, variait jusqu’à environ 50 %. Les valeurs prédictives négatives étaient plus élevées. Quarante-huit pour cent des sujets ayant une CP20 de 16 mg/mL ou moins déclaraient que le test reproduisait globalement leurs symptômes. Cette association était considérablement plus solide chez les femmes, les jeunes sujets et les personnes qui prenaient des stéroïdes en aérosol.
CONCLUSIONS :: En général, le test à la méthacholine reproduisait les symptômes pour lesquels le sujet était aiguillé. L’absence de symptômes spécifique (p. ex., dyspnée, toux, respiration sifflante ou oppression), dans la vie quotidienne ou au moment du test à la méthacholine, s’associait plus généralement à un test négatif que l’inverse. L’impression globale selon laquelle le test reproduisait ce que le patient expérimentait dans sa vie quotidienne s’associait de manière significative à un test positif (c’est-à-dire une CP20 de 16 mg/mL ou moins), l’association étant plus marquée chez les jeunes sujets et chez les femmes.
Comment in
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Recommended reading from the university of british columbia respiratory fellows and critical care fellows: respiratory fellowship program director: frank ryan; critical care fellowship program director: george isac.Am J Respir Crit Care Med. 2011 Sep 1;184(5):616-7. doi: 10.1164/rccm.201101-0143RR. Am J Respir Crit Care Med. 2011. PMID: 21885637 No abstract available.
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