Comprehensive geriatric assessment (CGA) is a valuable clinical instrument for detection of potentially health-threatening conditions in the elderly and it is independently associated with functional decline, rehospitalization, and death (1, 2). Objective measures of muscle function evaluation in CGA, such as gait speed and timed up and go test, are easily applicable and have good predictive capacity for clinical outcomes in this population (1, 3–6). However, the application of these tests is restricted to individuals with preserved walking ability, limiting its use in hospitalized patients. Therefore, there is a clear need for objective measures of muscle function evaluation that can be applied also for bedridden elders and that are equally capable of predicting rehospitalization and functional decline.

Point of care ultrasound, a fast, secure and non-invasive technique, has been applied in several clinical contexts, including the evaluation of changes in body composition associated with aging (7–9). This can be particularly useful to identify frail elders and to assess functional and mobility decline. Quadriceps muscle thickness and the proportion between the contractile segment of the thigh and the total anterior thigh thickness seem to be correlated with functional status and frailty (8) and, if correlated with gait speed and timed up and go test, would be a predictive variable applicable also for bedridden elders.

Considering the aforementioned reasons, this study was designed to evaluate the ability of quadriceps muscle thickness and the proportion between the contractile segment of the thigh and the total anterior thigh thickness, assessed with inhospital point of care ultrasound, to predict functional decline, rehospitalization, and death 3 months after hospital discharge, especially in bedridden patients.

Cohort of elder patients hospitalized in a medium complexity unit from a teaching hospital in southern Brazil was conducted to test for clinical outcomes. The inclusion criteria were 65 years or older hospitalized from June to September 2016. The exclusion criteria were impossibility to do point of care ultrasound of the quadriceps muscle for clinical reason (e.g., bilateral suprapatellar amputation of lower limbs) and impossibility to do the handgrip strength test for clinical reason (e.g., amputation of upper limbs).

To evaluate the reproducibility of the ultrasound method, a pilot transactional study was designed up in a sample of 23 patients. A workshop directed to all research team was held by a point of care ultrasound specialist. This training program comprised a theoretical session on the principles and techniques of point of care ultrasound and a subsequential 2 h supervised practice course.

After this training, each examiner performed three ultrasound measurements of the participants’ dominant thigh. All examiners were blinded for previous ultrasound results obtained by the other research team members. Intra and interobserver agreement analysis were then tested as described in the Section “Statistical Analysis.”

During the period from June to September 2016, 115 eligible patients were consecutively invited to participate in this study. Of those, 100 signed the Informed Consent Form and were included. Of those, the first 23 had their ultrasound measurements performed by three independent examiners and these measurements were used to perform agreement analysis. Of all the 100 participants, only 1 could not have a follow-up assessment in 3 months (not found).

Table 1 shows the baseline participants’ characteristics: 54% were female, 92% were white, 16% were illiterate, 33% had between 1 and 4 years of schooling, and 47% were widowers. Pneumonia was the main cause of hospitalization in this study (32%).

The bedside ultrasound method tested in this study for the evaluation of the anterior thigh of hospitalized elderly patients was easily applicable with good intra and interobserver agreement. It was also evidenced that both quadriceps thickness and the contractile index had significant correlation with gait speed, timed up and go, and handgrip strength. Beyond that, low quadriceps thickness predicted rehospitalization or death 3 months after hospital discharge and, as novelty and clinically relevant information, this finding remained significant among bedridden elderly. Associations tested were not significant after adjustments for age or sex, possibly because of lack of power to test for counfounding factors.

Previous studies have shown that reduction in skeletal muscle mass and strength occur throughout aging, even in the healthy elderly, and highlight the need for continued research into this age-related problem (16). Previous study also showed association between anthropometric measures, physical activity patterns, and outcome of mobility and falls (17). However, most of the available research findings regarding body composition in older patients were based in dual-energy X-ray absorptiometry (DXA), computed tomography (CT), or magnetic resonance imaging (MRI) as the measurement method (18–21). Given the relatively high cost of CT and MRI, the radiation exposure of CT and DXA, and the attractive qualities of ultrasound, such as increasing availability in hospital setting, low cost, easy transport, and radiation-free, the bedside ultrasound method to evaluate the anterior thigh should be considered in the prognostic evaluation of hospitalized elders as an alternative, safer, easily applicable and validated method.

More recently, the number of studies evaluating different clinical applications for bedside ultrasound has increased (7, 8). Mourtzakis and Wischmeyer (22) have applied bedside ultrasound to access body composition in the elderly population and describe the method as a useful tool to measure the muscle mass and the changes in muscle tissue. However, as novelty, this is the first study to validate a bedside ultrasound method of anterior thigh of hospitalized elders, including those unable to walk, that can predict rehospitalization or death as well as functional decline.

Several clinical conditions can compromise the global health status of a hospitalized elderly patient, increasing the inhospital and post-discharge morbimortality. The frailty syndrome is one of those. Elderly patients with this syndrome have lower functional reserve and higher incidence of negative outcomes such as rehospitalization and functional decline (23, 24). In the Cardiovascular Health Study (24), frailty was defined as the presence of three or more of the following five clinical criteria: weakness, poor endurance and energy, slowness, low physical activity level, and unintentional weight loss. This frailty phenotype and the accumulation of deficits throughout life (25) were able to predict falls, loss of mobility, functional decline in activities of daily living, as well as risk for hospitalization and death. However, it is composed by association of distinct subjective and objective clinical variables, some difficult to obtain, especially in hospital scenarios and in bedridden patients. Bedside ultrasound measurements of the anterior thigh, simple and easy clinical variables to obtain, tested as an alternative method to assess important prognostic factors in this study, were also correlated with mobility tests, functional decline and, most importantly, significantly associated with clinical outcomes in this sample of hospitalized elderly patients.

Gait speed and timed up and go test, objective measures of muscle function evaluation present in CGA, are easily applicable and have good predictive capacity for clinical outcomes in this population (1, 3–6). However, the uses of these tests are limited in hospitalized bedridden patients, a usually vulnerable population in which a physical objective evaluation can provide very useful clinical information. In this way, the most relevant result evidenced by this study according to the authors is that in bedridden hospitalized elderly patients, a low quadriceps thickness increased the risk for rehospitalization or death and, in this way, was able to additionally distinguish different prognosis profiles even among those vulnerable individuals, characterizing its novel clinical applicability. As far as we could investigate, this is the first study to validate a bedside ultrasound method of thigh evaluation in hospitalized elders and to present an objective evaluation of muscular functionality of hospitalized elderly unable to walk that can predict rehospitalization or death. This results brings a potential benefit of point of care ultrasound in the evaluation of hospitalized elderly patients, and may add significant value to the inhospital and post-hospital care of these patients, especially for identifying those with higher risk for negative outcomes.

Furthermore, low contractile index, a novel variable proposed and tested for the first time in this study, was able to predict functional decline 3 months after hospital discharge. The same was not observed for the quadriceps thickness variable. Because it represents the contractile segment of the anterior thigh over its entire thickness, and not just the isolated measure of quadriceps muscle thickness, the contractile index seems to better reflect the muscle reserve of the lower limb in comparison with the thickness of the quadriceps itself. In a geriatric care context, the capacity of contractile index to predict functional decline is a promising result and makes this a potential tool for the evaluation of hospitalized elderly patients. And, as authors hypothesize for future studies, it would help select potentially vulnerable patients for individualized care planning and clinical actions to prevent further functional decline.

The main limitation of the present study was the lack of power to test for independent associations regarding important theoretical confusion variables. Additionally, it is important to emphasize baseline characteristics that can interfere with external validity as the sample was provenient from a medium complexity hospital. Therefore, further studies with bigger sample size and longer follow-up period may be required for a more accurate assessment of the ability of ultrasound measurements of the anterior thigh to predict rehospitalization or death, functional decline, and to test its predictive capacity as a clinical instrument to be used as inclusion criteria in intervention studies.

In conclusion, the ultrasound method tested was easily applicable and reproducible. And, most importantly, it was able to demonstrate that the lower the contractile segment of the anterior thigh the greater the functional decline 3 months after discharge. Moreover, the quadriceps thickness measured by bedside ultrasonography was able to predict rehospitalization or death in all hospitalized elderly groups, including those bedridden elders, who were unable to walk. These results highlight this ultrasound method as a potential tool for prognostic assessment of hospitalized elderly, especially those unable to perform mobility tests.

This study was carried out in accordance with the recommendations of the “Resolution number 466 of the National Health Council of the Brazilian Ministry of Health” with written informed consent from all subjects. All subjects gave written informed consent in accordance with the Declaration of Helsinki. The protocol was approved by the “Hospital de Clínicas de Porto Alegre Ethics and Research Committee.”

RM: research protocol development and planning; protocol conduction and supervision; inclusion of participants; data analysis; interpretation of results; manuscript writing; and revisor leader. AG: research protocol development and planning; protocol conduction and supervision; inclusion of participants; bedside ultrasound examiner; data typing; interpretation of results; and manuscript writing. RO: inclusion of participants; bedside ultrasound examiner; data typing; interpretation of results; and manuscript writing. AT: research protocol development and planning; inclusion of participants; bedside ultrasound specialist; data analysis; interpretation of results; and manuscript writing and manuscript revision. RC: research protocol development; data analysis; interpretation of results; and manuscript writing. EM: research protocol development; interpretation of results; manuscript writing; and manuscript revisor.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer, PB, and the handling editor declared their shared affiliation, and the handling editor states that the process nevertheless met the standards of a fair and objective review.