Comparison of quantity and quality of muscle as clinical prognostic markers in patients undergoing carotid endarterectomy.

OBJECTIVE: The measurement of muscle area is routinely utilised in determining sarcopaenia in clinical research. However, this simple measure fails to factor in age-related morphometric changes in muscle quality such as myosteatosis. The aims of this study were to: firstly investigate the relationship between the masseter area (quantity) and density (quality), and secondly compare the prognostic clinical relevance of each parameter. METHODS: Cross-sectional CT head scans were reviewed for patients undergoing carotid endarterectomy. The masseter was manually delineated and the total masseter area (TMA) and the total masseter density (TMD) calculated. Measurements of the TMA were standardised against the cranial circumference. Observer variability in measurements were assessed using Bland-Altman plots. The relationship between TMA and TMD were evaluated using Pearson's correlation and linear regression analyses. The prognostic value of TMA and TMD were assessed using receiver operator curves and cox-regression analyses. RESULTS: In total, 149 patients who had undergone routine CT scans prior to a carotid endarterectomy were included in this study. No significant observer variations were observed in measuring the TMA, TMD and cranium circumference. There was a significant positive correlation between standardised TMA and TMD (Pearson's correlation 0.426, p < 0.001, adjusted R-squared 17.6%). The area under the curve for standardised TMA in predicting all-cause mortality at 30 days, 1 year and 4 years were higher when compared to TMD. Standardised TMA was only predictive of post-operative overall all-cause mortality (adjusted hazard ratio 0.38, 95% confidence interval 0.15-0.97, p = 0.043). CONCLUSION: We demonstrate a strong relationship between muscle size and density. However, the utilisation of muscle area is likely to be limited in routine clinical care. ADVANCES IN KNOWLEDGE: Our study supports the utilisation of muscle area in clinical sarcopaenia research. We did not observe any additional prognostic advantage in quantifying muscle density.

Validation of two-dimensional vertebral body parameters in estimating patient height in elderly patients.

OBJECTIVES: Standardised comparison of abdominal muscle and adipose tissue is often utilised in morphometric clinical research. Whilst measurements are traditionally standardised against the patient's height, this may not be always practically feasible. The aim of this study was to investigate the relationship between measurements of the vertebral body and patient height. METHODS: We analysed cross-sectional CT scans. Measurements of the vertebral body area (VBA), anteroposterior vertebral body diameter (APVBD) and lateral vertebral body diameter (LVBD) were made by two independent investigators by manual tracing. Patients were randomly divided into two groups: Group 1 standardisation and Group 2 validation. We compared height and vertebral body parameters from patients in Group 1 and mathematically modelled this relationship. We then utilised the model to predict the height of patients in Group 2 and compared this with their actual height. Observer variability was assessed using Bland-Altman plots and t-tests of differences. RESULTS: CT scans from 382 patients were analysed. No significant intraobserver or interobserver differences were apparent when measuring vertebral body parameters. We describe models which enable the prediction of the patients' height using the measured VBA, APVBD and LVBD. No significant differences were observed between the patients predicted and actual heights in the validation group. CONCLUSIONS: We demonstrate an important relationship between measurements of the patient's height and the vertebral body. This can be utilised in future research when the patient's height has not been measured. ADVANCES IN KNOWLEDGE: In the absence of the patient's height, we demonstrate that two-dimensional vertebral body parameters may be reliably used to standardise morphometric measurements.