American Lung Association Study Published in Latest Edition of "Journal of Allergy and Clinical Immunology" Identifies Racial Differences in Sensitivity to Methacholine

(July 17, 2012)

The Methacholine Challenge Test (MCT) has been widely used as a definitive test to assist in diagnosing asthma in patients with shortness of breath but normal results on regular spirometric testing. However, a recent study conducted by the American Lung Association Asthma Clinical Research Centers Network (ACRC)® – published in the Journal of Allergy and Clinical Immunology – found that, in a time of increased use of controller medications, the sensitivity (the proportion of those diagnosed with asthma correctly) of the MCT may be contingent on a patient’s racial and allergic state.

“Previous studies have indicated that MCT is a highly sensitive test, but these studies were conducted prior to the dissemination of the National Asthma Education Prevention Program guidelines, which advocated for the use of controller medications,” stated Norman H. Edelman, Chief Medical Officer of the American Lung Association. “With the increased use of inhaled corticosteroids in the treatment of asthma in recent years, it was unknown if the MCT still remained a valid diagnostic test for asthma”.

The ACRC investigators examined whether the MCT could differentiate 93 nonasthmatic participants from 126 participants with asthma receiving controller treatment, mainly inhaled corticosteroids. They found that only 77% of patients previously diagnosed with asthma by a physician displayed sensitivity to the MCT. However, the sensitivity of MCT in African American participants was 95%, compared to 69% in Caucasian participants. In addition, the sensitivity was 82% in those with atopy, defined as having one or more positive allergy skin test results, compared with 52% in those without.

“Although sensitivity and specificity values of previous MCT studies have varied depending on the population tested, the results of this study take both racial composition and effect of race into account, making it the first to show a racial difference in MCT diagnostic sensitivity between African Americans and Caucasians” states Kaharu Sumino, MD, MPH, co-PI of the ACRC at Washington University.

Reaching a medical diagnosis of asthma can be extremely challenging due to many varied symptoms and the lack of a precise diagnostic test. Results of this trial suggest that the MCT is an unreliable tool for conclusively excluding the diagnosis of asthma and should not be used as the sole method of diagnosis, especially in white and nonatopic patients.

Methapharm provided provocholine for the study.

The ACRC Network is an American Lung Association sponsored research program that conducts large scale clinical trials with the mission of advancing the care and treatment of people with asthma. The network, with a central data coordinating center and 18 clinical centers located across the country, is the largest nonprofit network of its kind. By placing numerous clinical centers nationwide, the ACRC Network is able to enroll large numbers of patients for clinical trials, thus ensuring relevant research findings can be interpreted with the highest level of scientific authority.

To learn more about the ACRC’s other important findings, promising new research going on in the network, and why clinical trials in research are so important in the latest edition of our Promise of Research e-newsletter. Want to keep up with research efforts of the American Lung Association? Subscribe here to receive future issues of Promise of Research. Want to keep up with all the Lung Association does to fight for healthy lungs and healthy air? Subscribe to our monthly Fighting For Air Online and other e-newsletters here.