CORR Insights®: Does a Prescription-based Comorbidity Index Correlate with the American Society of Anesthesiologists Physical Status Score and Mortality After Joint Arthroplasty? A Registry Study

About 85% of patients undergoing total joint arthroplasty have at least one medical comorbidity [³]. These conditions are independently associated with increased postoperative complications, discharge to destinations other than home (such as skilled nursing facilities), and even death after arthroplasty [⁸].

Over time, we’ve used certain scores like the American Society of Anesthesiologists (ASA) physical status score, the Charlson comorbidity index, and the Elixhauser comorbidity score to analyze the outcomes of patients with comorbidities. These scores are based on clinical assessments and hospital-coded diagnoses [^{4, 6}]. The Rx-Risk score [¹⁰] is another measure of comorbidity; it is based on prescriptions dispensed preoperatively. Elixhauser, Charlson, and Rx-Risk comorbidity measures were validated by Inacio et al. [⁷] as acceptable mortality predictors in THA and TKA patient cohorts. One study [¹¹] found that serum albumin also has a good predictive value for postoperative complications in these patients, with results comparable to ASA. Similarly, the 5-factor modified frailty index is also an independent predictor of postoperative complications and can be used for the same purposes [¹²].

The authors of the present study [⁹] analyzed the Rx-Risk score, which uses medication-dispensing records to stipulate the presence of comorbidities that are required to be managed by medications [^{5, 10}] and concluded that ASA and Rx-Risk were weakly to moderately correlated to each other. However, each score was highly associated with the probability of mortality shortly after undergoing a procedure.

The Rx-Risk score is readily available and may be a useful additional measure of a patient’s overall health, with the added benefit of defining the conditions for which a patient is receiving pharmaceutical treatment. Medication information may be useful to further understand risk factors in patients with the potential for poor functional outcome after joint replacement surgery. These may indeed be of great aid in eliminating the confounding factors while evaluating the probability of mortality shortly following major joint arthroplasties. Based on the results of the study, surgeons can do proper risk stratification, which may help when counseling patients and relatives or caregivers as well as when selecting patients for major joint arthroplasties