Monday morning’s session, "Updates to the Asthma Diagnostic Toolbox," packed a lot of material into one hour, exploring four key asthma diagnostic tools: The bronchodilator response, bronchoprovocation testing, FENO, and oscillometry.

The room nodded in agreement when one of the session hosts—Kevin Donahue, MD, said that diagnosing asthma isn’t all that cut and dry for a few reasons:

• Patients will sometimes present with a normal exam

• There are non-specific symptoms 

• There’s over- and under-diagnosis occurring

• International guidelines say confirmatory testing is recommended

• Lack of one gold standard test

To explore further, “The goal of the next hour is to dive into these individual tools and to dive into their nuances,” he said.

But the bronchodilator testing for diagnosis of asthma hasn’t been clear over the years—and is sometimes only 50% accurate. “A positive bronchodilator response has been defined as a 12% increase in the forced expiratory volume in one second (FEV1) or forced vital capacity (FVC) from their respective pre-bronchodilator values, combined with at least a 0.2 L absolute change,” according to a BMC Pulmonary Medicine study. 

But now, as Kaminsky said, “expressing the percent change in FEV1 and FVC relative to predicted normal values reduces the over-estimation of the bronchodilator response, especially in patients with a very low pre-bronchodilator FEV1, including in those with a ≥ 0.2 L change in FEV1. “

Despite the fluctuation in definitions over the years, Kaminsky says the test “doesn’t dictate our prescriptions….None of us are going to make a diagnosis of asthma and COPD with just a bronchoresponse test. Use clinical history….If someone doesn’t have a bronchoresponse doesn’t mean they don’t have an issue.”

Next, Nikhil Anand Huprikar, MD discussed bronchoprovocation (or, a methacholine challenge), saying that the test stops once FEV1 drops by 20% or more from baseline or when 400µg is hit. He also noted that guidelines suggest PD20 (the provocative dose of methacholine that leads to a 20% reduction in FEV1) over PC20 (the provocative concentration of MCh that results in the same), even though results may be comparable in both cases. Tidal breathing (versus deep) is recommended as well, he adds. 

“[The test] is not totally diagnostic of bronchial asthma,” Dr. Huprikar says. “You need clinical history as well.” Next, Linda Rogers, MD, FCCP discussed the fractional exhaled nitric oxide (FeNO) test. The majority of the room raised their hands when asked if they used the test.

Additionally, she shared that a diagnostic study found FeNO and eosinophil count could be used to diagnose eosinophilic asthma. That said, she says the values of FeNO values and thresholds still need work. “

Lastly, Dr. Donahue discussed oscillometry, saying it was a useful, noninvasive tool for detecting subtle disease, in pediatrics, or for older patients or those with neuromuscular issues, as it requires little effort on their behalf. “Peripheral airway dysfunction can be detected with oscillometry,” he said. Moreover, oscillometry is detected even in patients with normal spirometry—making it more sensitive. It also reduces the need for more methacholine.