Comparing the Performance of Calf Circumference, Albumin, and BMI for Predicting Mortality in Immobile Patients

Background: Immobile patients often suffer from malnutrition and low calf circumference (CC), a potential surrogate marker of low muscle mass, which has been widely explored as a link with mortality among patients with inconsistent results. In addition, studies comparing CC, BMI, and albumin to predict mortality among immobile patients are limited. The aim of our study was to compare the performance of these three parameters for predicting mortality among immobile patients.

Methods: This is a secondary analysis of our previous study consisting of immobile patients, age>18 years. Data were collected between November 2015 and March 2016 by trained nurses through a case report form (CRF) that included clinical data and sociodemographic variables. In addition, anthropometric parameters, including body weight, height and calf circumference, were also measured. The outcome of our study was mortality with follow-up length being 90 days. Multivariate linear and logistic regression analysis were adopted to identify the association between CC and mortality, and a receiver operating characteristic curve analysis was also used to compare the performance of CC, BMI, and albumin.

Results: Of the 387 patients who were included (51.42% male), with an average age of 61.22 (SD=15.18), the prevalence of mortality was 5.43%. The results showed that, after full adjustment, calf circumference was a protective factor for reducing the risk of mortality (OR=0.79; 95%CI:0.65-0.96). Meanwhile, immobile patients with low calf circumference had an increased risk of mortality, compared to those whose condition was normal (OR=4.24; 95%CI:1.07-16.74). Receiver operating characteristic curve analysis showed that CC combined with albumin (AUC=0.812; 95% CI=0.733-0.890) had the highest AUC value compared to calf circumference (AUC=0.759; 95%CI:0.662-0.856), BMI (AUC=0.653; 95%CI:0.538-0.767) and albumin (AUC=0.735; 95% CI:0.638-0.832), respectively, in predicting mortality in immobile patients.

Conclusion: The relationship between calf circumference and mortality was significantly negative and low calf circumference was associated with a high risk of 90-day mortality, compared to those with normal calf circumference. The combined calf circumference with albumin had good discrimination in predicting mortality among immobile patients. Therefore, it can routinely be used in a clinical setting by medical staff to predict mortality in immobile patients, as it is easy to obtain.