Evaluation of comorbidity scoring systems in patients undergoing knee arthroplasty.

Background: Ageing populations are increasing the demand for knee arthroplasty. Concurrently, the prevalence of medical comorbidities are rising too. The Self-Administered Comorbidity Questionnaire was developed to provide a patient's assessment of their own comorbidities whereas the American Society of Anesthesiologists grades and the Charlson Comorbidity Index utilise clinical evaluation to objectively measure perioperative morbidity and mortality risk. The primary aim of this study was to compare Self-Administered Comorbidity Questionnaire scores with American Society of Anesthesiologists grades and Charlson Comorbidity Index scores. The secondary aim was to compare Self-Administered Comorbidity Questionnaire scores with knee outcome scores.

Methods: A single centre observational cohort study of patients with knee osteoarthritis undergoing elective knee arthroplasty. Preoperative evaluation included Self-Administered Comorbidity Questionnaire scores, American Society of Anesthesiologists grades, Charlson Comorbidity Index scores and validated patient-reported outcome measures specific to knee surgery.

Results: A total of 141 patients were included in this study. Self-Administered Comorbidity Questionnaire scores were directly correlated with American Society of Anesthesiologists grade (rho = 0.37, p < 0.001) and Charlson Comorbidity Index scores (rho = 0.19, p = 0.047). Individual American Society of Anesthesiologists grades had significantly different Self-Administered Comorbidity Questionnaire scores (p = 0.001). Self-Administered Comorbidity Questionnaire scores were specifically associated with hypertension, ischaemic heart disease, chronic obstructive pulmonary disease and the total number of comorbidities, but American Society of Anesthesiologists and Charlson Comorbidity Index scores were associated with more comorbidities. Overall, Self-Administered Comorbidity Questionnaire scores were inversely correlated with patient-reported outcome measure scores.

Conclusion: Self-Administered Comorbidity Questionnaire scores are associated with increasing comorbidity in patients with symptomatic knee osteoarthritis; however, American Society of Anesthesiologists grades and Charlson Comorbidity Index scores had stronger and more abundant associations with comorbidities and patient-reported outcome measure scores. Self-Administered Comorbidity Questionnaires may complement but not replace current objective assessments of comorbidity when evaluating perioperative risk for knee arthroplasty.