Sensitivity of exercise testing for asthma in adolescents is halved in the summer.
OBJECTIVE
The exercise test is one of the most widely used challenge tests for asthma. It is not clear if the sensitivity of this test is lower when patients with asthma are not symptomatic. Since asthma activity is season dependent, with lower activity in the summer, we sought to determine if the percentage of positive exercise test results for asthma is lower in the summer as well.


METHODS
In this retrospective study, the proportion of positive exercise test results for asthma during each of the four seasons of the year, over a 5-year period, was compared.


METHODS
The study was conducted at the pediatric respiratory clinic and pulmonary function laboratory of Shaare Zedek Medical Center.


METHODS
The study group consisted of 532 consecutive patients, all 17 years of age, who were referred for exercise testing for evaluation of suspected asthma. All had normal baseline FEV1 levels, and none received maintenance asthma treatment.


RESULTS
Spirometry was performed before and after a standard exercise regimen. A decrease of > or = 10% in FEV1 after exercise was considered positive; 141 patients (26%) had a positive test result. The percentage of positive results in the summer (July to September quartile) was 12.9%, less than half the percentage of positive results during any of the other three quartiles (January to March, 28.9%, p < 0.05; April to June, 30.6%, p < 0.05; October to December, 29.1%, p < 0.05).


CONCLUSIONS
This study shows that the percentage of positive exercise challenge test results in the summer is half that of any other season. It is likely that the lower percentage of positive results for asthma in the summer reflects the lower sensitivity of the test during this season due to decreased asthma activity. We suggest performing exercise challenge testing only when patients are symptomatic. Physicians caring for patients with symptoms suggestive of exercise-induced asthma whose exercise test results are negative while asymptomatic should consider repeat exercise testing when their patients are symptomatic.
Goldberg
Shmuel
S
Department of Pediatric Pulmonology, Pediatric Respiratory Medicine, Shaare Zedek Medical Center, PO Box 3235, Jerusalem 91301, Israel. pedpul@szmc.org.il
Schwartz
Shepard
S
Izbicki
Gabriel
G
Hamami
Ronit Belisha
RB
Picard
Elie
E
D000293:Adolescent; D001249:Asthma / Q000503:physiopathology*; D005080:Exercise Test; D006801:Humans; D007557:Israel; D015203:Reproducibility of Results; D012621:Seasons