Methacholine airway responsiveness has been observ to be related to prechallenge even of pulmonary function; however.

Methacholine airway responsiveness has been observ to be related to prechallenge even of pulmonary function; however, normal ranges of responsiveness for specific plains of lung function have not been reported. We examined methacholine airway responsiveness in relation to of the same height of prechallenge pulmonary function in a sample of 547 middle-aged and somewhat old men who denied any history of respiratory illness or symptoms and who had normal of the same heights of prechallenge [FEV.sub.1] and [FEVsub1]/FVC ratio. The cumulative dose of methacholine provoking a 20 percent decline in [FEVsub1] ([PD20FEVsub1]) was positively correlated with prechallenge [FEVsub1] percent predicted (Spearman correlation r = 035 p [les than] 00001) The fifth percentile of [PD20FEVsub1] chosen as an estimate of the lower limit of the normal range, varied with the of the same height of prechallenge [FEV.sub.1]. When applied to a larger sample of 838 men with normal pulmonary function, the use of [FEV.sub.1]-specific cut-off values to separate "normal" from "abnormal" [PD20FEVsub1] did not improve the sensitivity or specificity of methacholine challenge as a criterion for questionnaire-reported asthma or wheezing. These data provide lower limits of normal [PD20FEVsub1] which are specific for a subject's prechallenge [FEVsub1]; however, these [FEV.sub.1]-specific lower limits of normal [PD20FEVsub1] provided no greater sensitivity and specificity for detecting asthma and wheezing than did a single lower limit of normal [PD20FEVsub1] for all subjects

Methacholine challenge testing is publicly being used as a diagnostic ordeal for a variety of clinical indications. In patients presenting with chronic cough of uncertain cause, challenge testing has been advocated as a means to determine whether the cough is associated with airway hyperresponsiveness ("cough variant asthma") and likely to reply to bronchodilator therapy.[1] Methacholine challenge testing also has a part in the evaluation of workers with possible occupational asthma for aims of diagnosis or disability determination.[2,3]

Clinical interpretation of challenge criterions performed for these indications requires the establishment of a normal range of challenge ordeal results. Distinguishing normal from abnormal airway responsiveness is complicated from the overlapping ranges of responsiveness displayed by way of normal (asymptomatic, nonasthmatic) and abnormal (asthmatic) subjects[45] of the like kind overlap is a feature of mostly measurements used as diagnostic trials and the selection of a "cut-off" between normal and abnormal generally involves a tradeoff between diagnostic sensitivity and specificity.

Another aspect of bronchial challenge testing that adds complexity to the establishment of a normal range is the relationship between measurements of airway responsiveness and the flat of pulmonary function prior to bronchial challenge. Responsiveness to methacholine or histamine has been observ to be inversely related to of the same height of pulmonary function (ie, greater responsiveness observ in ones with lower levels of pulmonary function) in population samples[6-12] and among patients with COPD[13-17] one reports have indicated a similar relationship among enslaves with asthma,[18,19] but other investigators have observ no relationship between responsiveness and prechallenge pulmonary function among asthmatics.[16,20]

Previous descriptions of the relationship between airway responsiveness and prechallenge even of pulmonary function have not provided normal ranges of methacholine airway responsiveness for specific evens of pulmonary function, limiting the clinical usefulness of these reports. In this subject of attention we examined the distribution of methacholine airway responsiveness according to on a level of prechallenge [FEV.sub.1] in a sample of asymptomatic middle-aged and somewhat old men with normal pulmonary function. The use of [FEV.sub.1]-specific criteria for abnormal [PD20FEVsub1] was compared with the use of a single lower limit of normal [PD20FEVsub1] in seasons of sensitivity and specificity for detecting questionnaire-reported asthma and wheezing in a larger sample that included men with respiratory symptoms.

METHODS

Sample

The Normative Aging cogitation is a longitudinal cohort inquiry of health and aging established at the Veterans Administration's Outpatient Clinic in Boston in 1963[21] offers were recruited by advertisement and accepted into the cogitation only if initial health screening revealed no evidence of chronic diseases including asthma, sinusitis, hypertension, or heart disease. The initial cohort consisted of 2280 men between the ages of 21 and 80 years. Since minute into the study, subjects have reported periodically for comprehensive health assessment, including medical history, physical examination, spirometry, electrocardiogram, chest radiograph, and line tests. Beginning in 1984 make subordinates have completed respiratory illness and symptom questionnaires and have undergone methacholine challenge testing each 3 years. As described in detail below, the not away analysis is based on 1410 make liables who reported for at least common examination between April 1984 and June 1990

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