The results of this study indicate that about 3 in 4 (74%) patients with mild asthma did have documentation of guideline-directed therapy. Previously reported adherence rates to asthma guidelines have varied. A 2016 study assessed primary care adherence to the previous 2007 NHLBI asthma guidelines. This study found that 88% of patients had documented guideline adherence for reliever medication and 70.4% had guideline adherence to maintenance medication [11]. Data on adherence to the more recent guidelines is available from an international study that assessed adherence via provider and patient surveys. This 2021 study examined asthma therapy in four countries (Australia, Canada, China, and the Philippines) and found that 47% of patients were on guideline-directed therapy [12]. Our study found a greater percentage of patients on guideline-directed therapy (74% compared to 47%). This may be due to the increased amount of time from the updated guidelines release and/or data collection methodology.

Information in Fig. 1 allows an assessment of which facility had the greatest patient population not receiving guideline-directed therapy, which may help target providers with education on guideline updates. As shown in the results and in Fig. 1, patients seen in the primary care setting (primary care, family medicine and internal medicine clinics) had the highest percentage of patients without guideline-directed therapy. This is valuable information as most patients with mild asthma will often be seen in a primary care setting due to the low severity of their asthma symptoms.

Regarding the secondary objective, patients in this study were found to be at a slightly greater risk for an asthma exacerbation if they were on guideline-directed therapy versus not; however, this objective was not statistically significant. The correlation of the timing of the asthma exacerbation and when the patient was started on guideline-directed therapy was unable to be determined based on the data gathered. During the study period, we assessed if the patient had an asthma exacerbation and if they were on guideline-directed therapy, but we did not assess the time at which these events occurred or in what order they occurred. In other words, during the study period, a patient who was not on guideline-directed therapy may have experienced an asthma exacerbation, and then was subsequently started on guideline-directed therapy. In addition, more acute or critical patients who were at a higher risk of having an asthma exacerbation may have been followed more closely by their practitioner which is why they were started on guideline-directed therapy sooner than other patients. Despite being followed more closely, they still had an asthma exacerbation due to being a higher risk patient. Finally, it is possible that some patients classified as having mild asthma actually have a more severe form of asthma and this may have contributed to the incidence of exacerbations.

Factors that were statistically significant with regards to exacerbation risk include female sex, GERD, and obesity. Previous studies have described morbidity and mortality risk factors for asthma, including high SABA use, increased age, ever smoking, and high blood eosinophils [13]. Few studies have specifically examined risk factors in patients characterized as having mild asthma. As discussed earlier, patients with mild asthma make up a large proportion of all patients with asthma, and these patients still experience exacerbations, but may not be treated with guideline-directed ICS therapy which is proven to reduce exacerbation risk [14]. Our study may add new insight into risk factors and treatment goals for patients with mild asthma, particularly optimizing treatment for GERD and obesity.

Despite Banner Health having a large patient population, the number of patients meeting our inclusion criteria was low. This may be suggesting a low prevalence of mild persistent asthma, low documentation of patients as having mild asthma, or more severe patients because of the large influence of the academic facilities on excluded patients. The lower than expected number of patients in this study may have limited the results.

Additionally, a limitation to the study was our inability to correlate the timing of patient exacerbations and medication use. As a result, the number of patients on guideline-directed therapy who experienced an asthma exacerbation may have been falsely elevated.

Another limitation to this study was that it was difficult to determine which provider or facility was managing therapy because patients could have been visiting multiple facilities within the institution or even outside the institution. Lastly, we are unable to be certain that each patient had the correct diagnosis code entered on their problem list. This was an assumption that the provider diagnosed the patient correctly and updated their problem list accordingly.

Accurately assessing patients with mild asthma may be a limitation of this study, as patients with more severe disease may have been classified as having mild asthma due to underreporting of symptoms by patients or failure to recognize severity by providers, particularly primary care providers.

Finally, the number of asthma exacerbations experienced by each patient is unknown based on the data gathered. This study only characterized patients as having an exacerbation or not having an exacerbation during the study period. In addition to this, patients seen at an outside facility for asthma exacerbation treatment would not be accounted for in our electronic health record. Patient adherence to medication is something we cannot determine from this study but could have an impact on exacerbations.