Development of a modified Cambridge Multimorbidity Score for use with SNOMED CT: an observational English primary care sentinel network study

Abstract

<jats:sec><jats:title>Background</jats:title><jats:p>People with multiple health conditions are more likely to have poorer health outcomes and greater care and service needs; a reliable measure of multimorbidity would inform management strategies and resource allocation.</jats:p></jats:sec><jats:sec><jats:title>Aim</jats:title><jats:p>To develop and validate a modified version of the Cambridge Multimorbidity Score in an extended age range, using clinical terms that are routinely used in electronic health records across the world (Systematized Nomenclature of Medicine — Clinical Terms, SNOMED CT).</jats:p></jats:sec><jats:sec><jats:title>Design and setting</jats:title><jats:p>Observational study using diagnosis and prescriptions data from an English primary care sentinel surveillance network between 2014 and 2019.</jats:p></jats:sec><jats:sec><jats:title>Method</jats:title><jats:p>In this study new variables describing 37 health conditions were curated and the associations modelled between these and 1-year mortality risk using the Cox proportional hazard model in a development dataset (<jats:italic>n</jats:italic>= 300 000). Two simplified models were then developed — a 20-condition model as per the original Cambridge Multimorbidity Score and a variable reduction model using backward elimination with Akaike information criterion as the stopping criterion. The results were compared and validated for 1-year mortality in a synchronous validation dataset (<jats:italic>n</jats:italic>= 150 000), and for 1-year and 5-year mortality in an asynchronous validation dataset (<jats:italic>n</jats:italic>= 150 000).</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The final variable reduction model retained 21 conditions, and the conditions mostly overlapped with those in the 20-condition model. The model performed similarly to the 37- and 20-condition models, showing high discrimination and good calibration following recalibration.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>This modified version of the Cambridge Multimorbidity Score allows reliable estimation using clinical terms that can be applied internationally across multiple healthcare settings.</jats:p></jats:sec>