Clinical, functional, and opportunistic CT metrics of sarcopenia at the point of imaging care: analysis of all-cause mortality.

PURPOSE: This study examines clinical, functional, and CT metrics of sarcopenia and all-cause mortality in older adults undergoing outpatient imaging. METHODS: The study included outpatients ≥ 65 years of age undergoing CT or PET/CT at a tertiary care institution. Assessments included screening questionnaires for sarcopenia (SARC-F) and frailty (FRAIL scale), and measurements of grip strength and usual gait speed (6 m course). Skeletal muscle area (SMA), index (SMI, area/height2) and density (SMD) were measured on CT at T12 and L3. A modified SMI was also examined (SMI-m, area/height). Mortality risk was studied with Cox proportional hazard analysis. RESULTS: The study included 416 patients; mean age 73.8 years [sd 6.2]; mean follow-up 2.9 years (sd 1.34). Abnormal grip, SARC-F, and FRAIL scale assessments were associated with higher mortality risk (HR [95%CI] = 2.0 [1.4-2.9], 1.6 [1.1-2.3], 2.0 [1.4-2.8]). Adjusting for age, higher L3-SMA, T12-SMA, T12-SMI and T12-SMI-m were associated with lower mortality risk (HR [95%CI] = 0.80 [0.65-0.90], 0.76 [0.64-0.90], 0.84 [0.70-1.00], and 0.80 [0.67-0.90], respectively). T12-SMD and L3-SMD were not predictive of mortality. After adjusting for abnormal grip strength and FRAIL scale assessments, T12-SMA and T12-SMI-m remained predictive of mortality risk (HR [95%CI] = 0.83 [0.70-1.00] and 0.80 [0.67-0.97], respectively). CONCLUSION: CT areal metrics were weaker predictors of all-cause mortality than clinical and functional metrics of sarcopenia in our older patient cohort; a CT density metric (SMD) was not predictive. Of areal CT metrics, SMI (area/height2) appeared to be less effective than non-normalized SMA or SMA normalized by height1.

Diagnosing sarcopenia at the point of imaging care: analysis of clinical, functional, and opportunistic CT metrics.

OBJECTIVE: To determine the relationship between CT-derived muscle metrics and standardized metrics of sarcopenia in patients undergoing routine CT imaging. MATERIALS AND METHODS: Data collected in 443 consecutive patients included body CT, grip strength, usual gait speed, and responses to SARC-F and FRAIL scale questionnaires. Functional and clinical metrics of sarcopenia were acquired at the time of CT. Metrics were analyzed using the diagnostic framework of the European Working Group on Sarcopenia in Older People (EWGSOP2). The skeletal muscle index (SMI) and skeletal muscle density (SMD) were measured at the T12 and L3 levels. Statistical methods include linear prediction models and ROC analysis. RESULTS: T12-SMD and L3-SMD in women and T12-SMD and L3-SMI in men show weak but significant (p < 0.05) predictive value for gait speed, after adjusting for subject age and body mass index. The prevalence of abnormal CT SMI at T12 and L3 was 29% and 71%, respectively, corresponding to prevalences of confirmed sarcopenia by EWGSOP2 of 10% and 15%, respectively. The agreement of abnormal SARC-F and FRAIL scale screening and EWGSOP2 confirmed sarcopenia was slight to fair (kappa: 0.20-0.28). CT cutpoints, based on EWGSOP2 criteria for abnormal grip strength or gait speed, are generally lower than cutpoints based on normative population data. CONCLUSION: Collection of clinical and functional sarcopenia information at the point of imaging care can be accomplished quickly and safely. CT-derived muscle metrics show convergent validity with gait speed. Only a minority of subjects with low CT metrics have confirmed sarcopenia by EWGSOP2 definition.