Tuberc Respir Dis.  2009 Oct;67(4):311-317.

Role of Methacholine PC20 in FEF(25-75%) for the Diagnosis of Bronchial Asthma

• Son KM
• Jang SH
• Kang HR
• Han B
• Kim JH
• Kim HS
• Park SH
• Hwang YI
• Kim DG
• Jung KS

Abstract

BACKGROUND
The methacholine bronchial provocation test is a useful tool for evaluating asthma in patients with normal or near normal baseline lung function. However, the sensitivity of this test is 82~92% at most. The purpose of this study is to evaluate the clinical usefulness of FEF(25-75%) in identification of airway hyperresponsiveness in patients with suspected asthmatic symptoms.
METHODS
One hundred twenty-five patients who experienced cough and wheezing within one week prior to their visiting the clinic were enrolled.
RESULTS
Sixty-four subjects showed no significant reduction of FEV1 or FEF(25-75%) on the methacholine bronchial provocation test (Group I). In 24 patients, FEF(25-75%) fell more than 20% from baseline without a 20% fall of FEV1 during methacholine challenge (Group II). All patients who had more than 20% fall of FEV1 (n=37) also showed more than 20% of reduction in FEF(25-75%) (Group III). Baseline FEV1/FVC (%) and FEF(25-75%) (L) were higher in group II than group III (81.51+/-1.56% vs. 75.02+/-1.60%, p<0.001, 3.25+/-0.21 L vs. 2.45+/-0.21 L, p=0.013, respectively). Group II had greater reductions of both FEV1 and FEF(25-75%) than group I at 25 mg/mL of methacholine (p<0.001). The provocative concentration of methacholine causing a 20% fall in FEF(25-75%) in group II was about three-fold higher than that in group III.
CONCLUSION
A 20% fall of FEF(25-75%) by methacholine provocation can be more sensitive indicator for detecting a milder form of airway hyperresponsiveness than FEV1 criteria.

Keyword

Methacholine; Bronchial provocation; FEF(25-75%)

MeSH Terms

Asthma
Bronchial Provocation Tests
Cough
Humans
Lung
Methacholine Chloride
Respiratory Sounds
Methacholine Chloride

Figure

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  Figure 1 Inter-group comparison of airway hyperresponsiveness. (A) Percent falls of FEV1 and FEF25-75% at 25 mg/mL of methacholine were significantly larger in group II than in group I. (B) †FEF25-75%-PC20 was about thrice higher in group II compared with group III. The results are expressed as mean±SEM. *p<0.001, t-test. †FEF25-75%-PC20 denotes provocative concentration of methacholine causing a 20% fall in FEF25-75%.

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  Figure 2 Association of airway hyperresponsiveness and sputum eosinophilia. (A) The patients with sputum eosinophilia more frequently had positive result in methacholine provocation test based on either FEV1 or FEF25-75% *p=0.002, †p=0.007, Pearson's chi-square. (B) The difference of FEV1-PC20 was insignificant between the patients with sputum eosinophilia and without sputum eosinophilia (p=0.203), but FEF25-75%-PC20 was significantly lower in the patients with sputum eosinophilia than in the patients without sputum eosinophilia (*p=0.032, t-test). The results are expressed as mean±SEM.

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