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| |  New Test Shows Promise for Diagnosing Asthma in Children: Presented at AAAAI By Carole VanSickle Ellis NEW ORLEANS -- March 3, 2010 -- Physicians looking for an alternative to methacholine when identifying exercise-induced bronchoconstriction (EIB) and establishing a physician’s diagnoses of asthma in children with symptoms and without a previous diagnosis may have their answer in mannitol powder. In a test group of 96 children aged younger than 18 years with signs and symptoms suggestive of asthma but without a firm diagnosis, mannitol powder was equivalent to methacholine in identifying EIB and asthma. The study was presented by Sandra D. Anderson, MD, Royal Prince Alfred Hospital, Camperdown, Australia, here at the 2010 American Academy of Allergy, Asthma & Immunology (AAAAI) Annual Meeting on February 27. While methacholine has long been the “go-to” for diagnosing asthma in both children and adults, it has some drawbacks in terms of recovery time after the test, coughing, and chest discomfort that mannitol does not necessarily exhibit to the same degree. However, Dr. Anderson points out, the biggest advantage that a mannitol kit has over methacholine is that it is “so easy that you can carry it around in your pocket.” The single-use, disposable test capsules are premeasured so that as increasing doses are inhaled 60 seconds apart, the osmolarity of the airway surface liquid increases, allowing for a decrease in forced expiratory volume in 1 second (FEV1). The mannitol kits have 9 dose steps at 0, 5, 10, 20, 40, 80, 160, 160, and 160 mg. FEV1 was measured 60 seconds after each dose. In the methacholine challenge, methacholine was delivered from a nebuliser by dosimeter method at concentrations of 0.0312, 0.0625, 0.125, 0.25, 0.5, 1, 2, 4, 8, and 16 mg/mL. Every concentration required 5 inhalations to total lung capacity and spirometry was performed within 3 minutes. An exercise test was also performed. FEV1 was measured at 5, 10, 15, and 30 minutes after exercise, with the better of 2 attempts recorded. Both mannitol and methacholine were similar in sensitivity for identifying EIB and in establishing a physician’s diagnosis of asthma in children who have symptoms but, as yet, no diagnosis. Both performed better than the exercise tests. However, after the mannitol test, the percent-fall in FEV1 and recovery time after a positive test was less when compared with methacholine and the specificity for a physician diagnosis was higher for mannitol than methacholine. Both methods showed a similar incidence of adverse events. Mannitol powder is presently available in Europe and Australia and is currently being evaluated by the US Food and Drug Administration.
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