The original framework proposed by Piette and Kerr10
centered on diabetes as the chronic condition of interest. In our study, we centered on heart disease, and more specifically, on ambulatory treatment following an acute myocardial infarction. In our analysis, focused on care for patients who have recently had an AMI, we found that more concordant conditions, i.e., those with more pathophysiologic and management overlap with the post-AMI condition of interest in this analysis, increased the likelihood that patients received treatments recommended by guidelines for patients with ischemic heart disease; conversely, when co-morbid conditions were not concordant, guideline-recommended AMI treatments were less likely received. However, the expected associations between a condition being symptomatic and guideline adherence being higher were less consistent, and the magnitude of the associations was not large.
We find the Piette and Kerr framework useful for two reasons: first, it could help order co-morbid conditions and force more thoughtfulness about how patients with multiple chronic conditions could be treated. Second, by offering testable propositions, if the framework has empirical foundation and if a direct link to improved outcomes is found, it could be used in the future to target patient groups or providers for education and knowledge translation activities to promote improved adherence to guideline recommendations. It can also provide a framework to improve the degree to which the guidelines take into account co-morbid conditions that are not concordant with post-AMI treatment guidelines, or attempt to improve recognition of asymptomatic conditions. For both these reasons, we believe that further investigation similar to ours, but focusing on different “centering” chronic conditions is essential. In addition, longitudinal studies in which temporal sequencing can be measured definitively are also important for establishing causality.
Issues of concordance depend heavily on which disease or health problem is the center of the investigation. To a patient who is classified “with diabetes” primarily, heart disease is a co-morbid condition. Conversely, to a post-AMI patient, diabetes is co-morbid. While the question of which disease is used to center the observations is important for assessing concordance of co-morbid conditions, it should not affect symptomaticity of co-morbid conditions that are characteristics of the co-morbid condition, not of the condition of focus. This observation may explain the unexpected findings in terms of symptomaticity, in that the indicators on which the quality score for guideline adherence are based are focused on the post-AMI condition, not the co-morbidity. Because the post-AMI condition is, by definition, symptomatic in this group (even though in general, ischemic heart disease is often asymptomatic, these patients were recently diagnosed with AMI), one might not expect asymptomaticity of the co-morbid condition to diminish adherence to indicators for the post-AMI condition, as long as the co-morbidities are concordant. This is, indeed, what we observed with hypertension and hyperlipidemia.
Our finding that the sign on the symptomatic score changed direction when we included both concordance and symptomatic scores in the model suggests that there is a complex relationship between the two scores. The fact that neither interaction nor multi-collinearity explains this result leads us to conclude that including one score without the other in a model is likely to lead to omitted variable bias, or confounding. We do not have a clear explanation for this relationship, and we believe that this finding should be tested by others using more robust methods for obtaining the scores, as we note in our Limitations section. This relationship may be specific to post-AMI care and the set of co-morbid conditions that may affect guideline-recommended care specific to this health problem.
Despite the utility this framework might have for clinical practice in the future, we should perhaps also be seeking to develop a different kind of framework. The health-care community is beginning to acknowledge that the presence of multiple chronic conditions in an individual patient may alter the optimal approach to each of these conditions for that individual. A framework that would aid in prioritizing treatments without being centered on a single condition might be very useful clinically. While our symptomatic score is independent of the “centering” condition in a framework à la Piette and Kerr, our concordant score is clearly dependent on the centering condition. In parallel with efforts to refine the current model, we should also perhaps think about “meta-guidelines” that are not based on a single condition or diagnosis or on the simple juxtaposition of condition-specific guidelines.
There are limits on the generalizability of our findings. Our data come from one state and from patients whose physicians participated in the longitudinal study of an educational intervention to improve post-AMI care. Although this is a limitation, in the context of an exploratory study to assess the application of a new theoretical framework to understand characteristics of co-morbid conditions and adherence to guideline-recommended treatments, it is reasonable to begin with low generalizability. A more serious limitation is that we used a limited sample of clinicians to rate the co-morbid conditions to derive the weights used to score concordance and symptomaticity. While this is a serious limitation, and a more robust exploration of the phenomenon we are investigating will require a more robust approach to assessing weights, we believe that our panel of clinicians was expert and that it is likely that replication will confirm most of the weights we used. There are also some issues related to contraindications for some post-AMI guideline recommendations, such as the possibility that clinicians may consider ACE inhibitors contraindicated in patients with chronic kidney disease. We believe that it is very important for further research to be conducted to assess the relationships we report in different post-AMI samples as well as in other chronic conditions. Finally, our analysis extends only to whether or not a guideline-recommended medication was prescribed, not whether or not it was taken by the patient. Full compliance with guideline-recommended therapies requires both provider and patient action. In this study, we could only assess provider action.
A consensus is emerging that guidelines and evidence on which to base treatment decisions need to take into account the realities of highly co-morbid, complex patients being cared for by providers in our health-care systems. There are competing hypotheses that may explain some of these findings, and we believe that further investigation along these lines will yield promising new insights and approaches. Possible approaches may include the ability to target patient groups for more specific interventions to improve adherence to guideline-recommended care or the development of new guidelines that are not single condition-specific and may aid in prioritizing evidence-based treatment.