Chest
Volume 82, Issue 1, July 1982, Pages 15-18
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Clinical Investigations
A Screening Test for Airways Reactivity: An Abbreviated Methacholine Inhalation Challenge

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A screening test to measure nonspecific airways reactivity was developed and compared to a standard methacholine inhalation challenge in 13 asthmatic patients and ten normal control subjects. The screening challenge consisted of one deep breath, then four breaths of a 5 mg/ml methacholine solution followed by one and four breaths of 25 mg/ml of methacholine. Subjects with a history of wheezing received the 5 mg/ml of methacholine first while those without a history of asthma began the challenge at the 25 mg/ml methacholine concentration. Spirometric tests were employed and the challenge was terminated when FEV1 fell 20 percent from baseline. The standard methacholine challenge used a dosimeter and all subjects took five breaths of saline solution followed by seven increasing concentrations of methacholine. Dose response curves were constructed and the provocation dose of methacholine that caused a 20 percent fall in FEV1 was calculated for each protocol. Results of the screening methacholine challenge correlated with those obtained from the more lengthy standard protocol (r=0.94), and correctly identified levels of airways reactivity in asthmatic patients and normal subjects. The abbreviated protocol was rapid (6–12 min), safe, and inexpensive. Since the equipment is readily available and easy to transport, it could be used at sites outside the hospital as a screening test for nonspecific airways reactivity.

Section snippets

METHODS

The study population consisted of 13 asthmatic patients (eight men and five women, 19 to 30 years of age) with a characteristic clinical history of asthma,12 and ten normal control subjects (six men and four women, 21 to 37 years of age) who had no history of asthma, atopy, or allergic rhinitis. No asthmatic patients had taken glucocorticoids or sodium cromolyn for at least four weeks prior to our study, while short-acting methylxanthines, sympathomi-metics, and antihistamines were withheld for

RESULTS

Results of baseline pulmonary function tests in both the normal subjects and asthmatic patients were similar on each of the two study days for the standard and the short methacholine challenge (P > 0.7). Figure 1 shows the relationship between the PD20 FEV1 calculated using the short methacholine challenge test and the PD20 FEV1 measured by the standard methacholine protocol. The correlation by rank order analysis was R = 0.94 (P < 0.001) for all subjects and R = 0.77 (P < 0.01) for the

DISCUSSION

This short methacholine challenge protocol accurately assessed airway hyperreactivity in asthmatic subjects and provided results similar to those obtained with a standard, more lengthy, methacholine inhalation challenge technique. Furthermore, it has several advantages for use as a screening test. It is simple to perform, rapid (6–12 minutes), and requires only routine, inexpensive pulmonary laboratory equipment. The training period for both subjects and technicians is negligible. In even the

ACKNOWLEDGMENT

The authors would like to thank Brenda Jordan and Betty Giacomazza for their secretarial assistance in the preparation of this manuscript.

REFERENCES (14)

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Supported by The National Heart, Lung and Blood Institute Specialized Center for Research in Pulmonary Diseases Grant HL-14153, and by The Institute of Allergy and Infectious Diseases Grant AI-10304

Manuscript received October 29; revision accepted December 18.

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