A test used for screening for asthma in patients without previous symptoms is not “reliable” for diagnosing the respiratory condition, according to researchers.
Based on their findings, the authors of the new study, from Australia, have urged caution in the use of the mannitol challenge test for asthma in non-clinical settings.
“Our study highlights the need for caution when interpreting results”
They noted that the mannitol challenge test was a cost-effective and easily applied test to detect if the airways were more likely to contract or narrow more than normal, which is associated with asthma and airway inflammation.
During a mannitol challenge test, the subject inhales increasing doses of mannitol in powder form, with their lung function measured after each dose to determine the level of bronchial hyper-responsiveness.
While the test was considered widely applicable to detect asthma, the researchers highlighted that its accuracy outside of patients referred for specialised respiratory care had not been thoroughly explored before.
In the 772-participant study, the test results were as expected in people who reported wheezing, but it had a relatively low predictive value for asthma in the general population.
As a result, the findings meant that within the general population, a positive test result could not reliably detect asthma, said the authors in the journal Respirology.
“The mannitol challenge test is increasingly used to screen for asthma in groups such as defence force recruits, athletes, and asymptomatic young people participating in sports,” said senior study author Dr Graham Hall, from the Telethon Kids Institute in Perth.
He added: “Our study highlights the need for caution when interpreting results of this test in non-clinical populations.”