Secondary diagnostic verification of asthma in adults with an asthma diagnosis may improve quality of life (QoL) and reduce costs, according to study results published in The Journal of Allergy and Clinical Immunology.
A probabilistic time-in-state cohort model was developed to compare a stepwise asthma verification algorithm based on spirometry and methacholine challenge test (MCT) results with the current method of care. Researchers used a simulated cohort of patients aged ≥15 years with a self-reported physician diagnosis of asthma (N=10,000). The primary outcomes were the incremental costs and quality-adjusted life-years (QALYs) associated with the use of diagnostic verification as compared with the current standard of care (ie, the continuation of asthma management without any further evaluation of diagnosis).
The first step in the 2-stage diagnostic verification algorithm intervention was spirometry with reversibility testing before and after inhaled bronchodilation. Asthma was verified if the forced expiratory volume in 1 second improved by ≥12% and by 200 mL.
In the stepwise verification scenario, asthma diagnosis was confirmed through spirometry alone in 1500 patients. Among the 8500 patients who would undergo a subsequent MCT, the asthma diagnoses would be confirmed in 4760 patients. In the remaining patients for whom spirometry and MCT would be negative (n=3740), asthma would be ruled out, and 374 diagnoses would be erroneously reversed. Using parameters from published literature, the removal of diagnosis in 3366 patients correlates to a savings of $36.26 million in direct costs and gain of 4049 QALYs over 20 years. When extrapolated to 2018 costs in the United States using historical inflation rates, the researchers calculated an undiscounted potential savings of $56.48 billion over 20 years.
This study had several limitations. One limitation was that the main source of the data was a Canadian study, and the lack of a US-based study prevented the researchers from comparing US and Canadian rates of asthma overdiagnosis. However, a recent systematic review reported that studies across different jurisdictions have consistently reported similar overdiagnosis rates. These results do not pertain to alternative schemes such as a systematic screening program, because it was assumed that diagnostic verification will take place in the context of routine clinical practice. The researchers acknowledged that strict adherence to the diagnostic verification algorithm might not be achieved in the real practice; departures from the verification protocol will inevitably affect its cost-effectiveness. In extrapolating the results to the entire US population, immediate uptake of the algorithm was assumed, while in reality, there will be gradual adoption. Also, the researchers did not consider less robust alternative diagnostic strategies. The efficiency of the proposed intervention could be affected by changes in risk factors as well as future innovations in asthma diagnosis.
“The overall conclusions made in this study about the merits of such diagnostic verification remained robust against changes in assumptions and parameter values,” the researchers concluded. “Nevertheless, evidence on the performance of diagnostic verification largely comes from research settings, some of which from countries other than the US. As the ‘real world’ adherence to, and performance of, stepwise diagnostic algorithms remain untested, future implementation of such algorithms should also be coupled with subsequent evaluations.”
Disclosure: This study was supported by MethaPharm, Inc. Please see the original reference for a full list of authors’ disclosures.
Yaghoubi M, Adibi A, Zafari Z, et al. Cost-effectiveness of implementing objective diagnostic verification of asthma in the United States [published December 11, 2019]. J Allergy Clin Immunol. doi:10.1016/j.jaci.2019.11.038