We validated a case definition for combined suspected or confirmed asthma in primary care. This study's proposed case definitions had similar results for both suspected and confirmed asthma. Case definitions could not discriminate between suspected and confirmed asthma because the use of objective measures to confirm asthma diagnosis was either not completed or not documented. This highlights the importance of confirming and documenting the status of asthma diagnoses in EMRs. Until EMR data elements are adopted that allow for the distinction between suspected and confirmed asthma, one case definition that can be used for combined suspected or confirmed asthma is recommended.
Our proposed case definitions had similar operating characteristics to those reported previously. However, in replicating case definition algorithms from both Xi, et al. (2015)10 and Cave et al. (2020)11 (Table 1), we found different results across all metrics calculated. For example for Case Definition 1, Xi et al. (2015) report a SN of 78% and SP of 89%, compared to a SN of 35% and SP of 99% in our study. For Case Definition 3, Xi, et al. (2015) reported a SN of 7% and SP of 99%, compared to a SN of 4% and SP of 100% in our study.10 Case Definitions 1 and 3 were attempts to replicate their algorithms and were considered approximated because the original case definition algorithms used information directly from the source EMR in OSCAR. For Cave et al. (2020), the metrics were similar, with a reported a SN of 83%, SP of 99%, PPV of 74%, NPV of 99%, and a Youden’s Index of 0.82, compared to a SN of 78%, SP of 97%, PPV of 75%, NPV of 98%, and YI of 0.73 in our study.11
This variability can likely be attributed to the variation in the data sources used for case definition analysis and the variation in charting behaviour between clinical sites. Xi et al. (2015) created a cohort with a high proportion of patients with asthma and COPD for analysis. In contrast, we used a population-based sample, thus having a lower asthma prevalence, reducing SP and PPV while improving SN and NPV. In Cave et al.’s (2020) study, the authors used data from the Southern Alberta Primary Care Research Network of CPCSSN (SAPCReN-CPCSSN) to classify cases of asthma. In this study, reviewers used the source EMR for classification, allowing for a complete review of the patient’s entire medical history.
The results of this study highlight the importance of having discrete data elements for asthma diagnostic tests in EMRs, particularly given that there were no searchable data elements that enabled us to differentiate between suspected and confirmed asthma. As such, EMRs should incorporate data elements such as those proposed by the Pan-Canadian Respiratory Initiative for Electronic Health Records (PRESTINE) for providers to be able to document whether asthma is suspected or confirmed, and if confirmed by what method6,13. This would enable search strategies to differentiate between suspected and confirmed asthma.14 By adopting these data elements, knowledge translation eTools could provide decision support to healthcare providers on cases of suspected asthma that require objective testing, while simultaneously improving asthma surveillance by ensuring cases of asthma are confirmed asthma15.
In our study, although we included every medication combination presented in the CTS guidelines for asthma management2 (Case Definitions M1-M7), medication data did not improve the operating characteristics of detection algorithms (Table 1). The proposed case definitions that included medication data had a wide sensitivity range, from 0 to 76%. This result differs from previous literature on asthma case definitions, which discuss adding medications as an effective way to improve case definitions.16 We believe that this may be because many medications are being used for both asthma, COPD, and allergic rhinitis.
The findings of our study fit well within the existing literature on the validation of asthma diagnoses using EMRs. A recent study from Howell et al. (2022)17 developed a case definition algorithm for asthma using EMR data from a pulmonary specialty clinic. This study’s best-case definition had a SN of 94% and a SP of 85%. These results are slightly higher than the results of our study. In this case, the slightly higher SN and SP can be attributed to using a specialty clinic, which would be more likely to have confirmed cases of asthma, improving specificity, and a higher relative proportion of patients with asthma, improving sensitivity. Another systematic review of literature on the validation of asthma diagnoses in electronic health records by Nissen et al. (2017) described 13 studies on the subject.16 The authors found that most studies were able to demonstrate a high positive predictive value (PPV > 80%), with a high degree of variation based on methodology used. Our study builds upon the systematic review by using a national database that can utilize the case definition in primary care practices across Canada.
We were able to directly replicate the case definition proposed by Cave et al. (2020), given that it also used CPCSSN data holdings. For case definition 13, Cave et al. (2020) reported a SN of 83% (+ 5%), a SP of 99% (+ 2%), PPV of 74% (-1%), NPV of 99% (-1%), and a Youden’s Index of 0.82 (+ 0.09), which are nearly identical to our results. The discrepancy between the findings can be attributed to the data source used for classifying cases of asthma and the data source used for validating the case definition.
Strengths
Strengths of this study include using the original EMR source data for chart abstraction and classification. By manually reviewing the patient chart, the abstractor and physicians had the entire medical record of a patient available to accurately classify the charts based on all information available. Another strength of this study is the use of CPCSSN data holdings for testing and validating case definitions. CPCSSN data is more granular than health administrative data that has been used for case definitions of asthma in the past, yet more broadly applicable than data from a single EMR.18 An additional feature of this study is the use of a single abstractor and experts for classification purposes, which ensured consistency in both data collection and final classification of cases throughout the study.
Limitations
Limitations of this study include generalizability and the data source. This exercise was conducted at a single academic clinical site that is a member of CPCSSN. It may be difficult to generalize the findings at this academic primary care practice to community practices, as the case mix may differ, and this particular practice may have unique charting, billing, and data entry patterns. Additionally, this study used information from one EMR, OSCAR. As a result, the case definitions developed in this study may have different results when applied to other EMRs, although the criteria used in the CPCSSN database applies to sites across Canada.