Body fat percentage assessment by ultrasound subcutaneous fat thickness measurements in middle-aged and older adults

Intra- and inter-rater reliability of muscle and fat thickness measurements obtained using portable ultrasonography in older adults

BACKGROUND & AIMS

Ultrasonography (US) is a promising tool for assessing body composition, offering accuracy and accessibility. However, technician skills and equipment characteristics can impact measurement reliability. We aimed to evaluate the intra- and inter-rater reliability of two evaluators using A-mode Portable Ultrasound to measure muscle and fat thickness in Brazilian older adults.

METHODS

Quantitative cross-sectional study carried out with 150 community-dwelling older adults of Campinas-SP-Brazil, recruited in a retirement preparation program and a geriatric outpatient care unit. Scans of nine anatomical points were performed using the portable ultrasound in A-mode (BodyMetrix Pro System BX2000; Livermore, CA), with 6 scans per location and 3 measurements taken by each evaluator. After the selection and analysis of the generated images, muscle and fat thickness were measured. Reliability estimates between measures of the same evaluator (intra-rater) and between evaluators (inter-rater) were assessed using intraclass correlation coefficients (ICC), and differences within and between technicians were assessed using one-way ANOVA. Analyses were carried out for the overall sample and stratified by sex and by nutritional status.

RESULTS

Excellent ICC values (>0.90) were found for subcutaneous fat thickness in intra- and inter-rater reliability analyses. The lowest ICC values were observed for deep abdominal fat thickness measured by evaluator 1 (ICC = 0.90) and evaluator 2 (ICC = 0.87), as well as in the inter-rater analysis (ICC = 0.85). Muscle thickness measurements had satisfactory ICC values for triceps, biceps, anterior thigh, and calf, ranging from moderate to good (ICC 0.50-0.90).

CONCLUSION

A portable A-mode ultrasound demonstrates excellent reliability among both intra- and inter-raters for assessing fat thickness but only moderate for muscle thickness in older adults. Hence, this could prompt inquiries regarding the sole reliance on this tool for quantifying muscle mass and examining sarcopenia in older adults. To our knowledge, this study represents the first assessment of reliability for a portable A-mode ultrasound device conducted with older adults.

Relationship Between Dual-Energy X-Ray Absorptiometry, Ultrasonography, and Anthropometry Methods to Estimate Muscle Mass and Muscle Quality in Older Adults

Decreased muscle quality (MQ) may explain functional capacity impairments during aging. Thus, it is essential to verify the interaction between MQ and functional capacity in older adults. We investigated the relationship between MQ and functional capacity in older adults (n = 34; 66.3 ± 4.6 year). MQ was estimated by maximum strength of knee extensors normalized to thigh muscle mass. Maximum strength was assessed on an isokinetic dynamometer (peak torque), while dual-energy X-ray absorptiometry (DXA), ultrasonography, and anthropometry were used to determine thigh muscle mass. Functional capacity was verified by 30-s sit to stand and timed up and go tests. Significant correlations were found between MQ assessed by DXA with 30-s sit to stand (r = .35; p < .05) and timed up and go (r = -.47; p < .05), and MQ assessed by anthropometry with timed up and go (r = -.41; p < .05), but not between MQ assessed by ultrasonography with functional capacity (p > .05). No significant relationship between muscle mass with functional capacity was observed. Thus, MQ assessed by DXA and MQ assessed by anthropometry may partially explain functional capacity in older adults. Interestingly, muscle mass alone did not explain performance in functional tests in this population.

Utility of high-resolution ultrasound in measuring subcutaneous fat thickness

OBJECTIVE

Previous studies conclude that high-resolution ultrasound (HRUS) enables noninvasive and accurate measurements of subcutaneous fat thickness. The primary objective of this cross-sectional study was to better characterize subcutaneous fat thickness measurements in a diverse patient population using HRUS. Secondarily, we sought to correlate these measurements with patients' body image.

METHODS

A cross-sectional study to measure subcutaneous fat measurements at seven distinct anatomic sites, including upper and lower extremities, submental, and torso regions, in 40 men and women of different ages and races using HRUS. Independent t-tests and analysis of variance were performed to analyze findings.

RESULTS

In our patient population, on average, women had thicker subcutaneous fat than men at all anatomic sites. Asian patients had significantly reduced fat thickness at peripheral anatomic sites, such as arms when compared to patients who identified as Black and Other (p = 0.05 and p = 0.008, respectively). Lastly, women reported decreased total body satisfaction at all anatomic sites when compared to men.

CONCLUSION

The information obtained and methods developed in this study may be utilized clinically during patient selection for fat reduction procedures, including for estimating the degree of likely benefit; for managing pathologies involving subcutaneous fat thickness alteration; and to monitor the progression of lipodystrophy secondary to disease or drugs.

Ultrasonographic measurement of abdominal and gluteal-femoral fat thickness as a predictor for android/gynoid ratio

OBJECTIVE

To evaluate the use of ultrasonography (US) as an alternative to dual-energy x-ray absorptiometry (DXA) to predict the percentage ratio of android/gynoid (A/G) fat mass.

METHODS

This was a cross-sectional study. Twenty-eight participants included in the study underwent whole-body DXA examinations and the A/G ratio was calculated. Soft-tissue US was performed in several standardised anthropometric areas of the body. Correlation analysis between abdominal and gluteal-femoral fat thickness based on US and A/G ratio was conducted using the Pearson or Spearman test depending on the data normality. Multiple regression analysis using the backward stepwise method was performed to establish an equation for estimating the A/G ratio.

RESULTS

There was a strong and significant correlation between fat thickness in the six anthropometric areas and the A/G ratio in female participants. The analysis revealed three anthropometric areas: upper abdomen (S4), lower abdomen (S5), and mid-xiphoid-umbilical region (S7), that can accurately predict the A/G ratio by 82.3%. (P < 0.05). However, no such correlation was found in male participants.

CONCLUSIONS

US measurement of fat thickness can predict A/G ratio in the female population. However, this method is not recommended for men.

Assessment of Body Fat Percentage Using B-Mode Ultrasound Technique versus Skinfold Caliper in Obese Healthy Volunteers

Background and aims

The measurement of the skinfold thickness at various sites with the calipers has remained the traditional method for estimation of body fat percentage (%BF) in clinical practice. Although this technique is relatively inexpensive and easy to learn, there are more chances of errors while measuring the skinfold thickness by this method. Therefore, no single standard prediction formula for the determination of body fat could be fixed. The aim of our study was to use B-mode ultrasound (US) for measuring the subcutaneous fat thickness and the calipers for skinfold thickness, and then compare, correlate, and derive the prediction equations for estimation of %BF by both the techniques.

Methods

This cross-sectional, observational, monocentric study was conducted on 43 Indian male volunteers aged 18 to 40 years. After collecting anthropometric data (age, height, weight, body mass index, waist circumference, hip circumference, waist-to-hip ratio [WHR], etc.), the skinfold thickness was measured at four standard sites (biceps, triceps, subscapular region, and suprailiac region) with skinfold caliper (SFC) and then B-mode US. The data were analyzed for distribution, and independent t-test was applied to compare the difference between two means of a %BF estimated by both the methods. The prediction equations were developed from anthropometric and skinfold thickness data obtained from both the methods, i.e., SFC and US, by applying stepwise multiple linear regression.

Results

It was observed that mean values of all the skinfold thicknesses along with the %BF measured by SFC were far more than those measured by US. The %BF measured by US technique (%BF US) was significantly lesser, i.e., 20.69 (SD: 3.126; p < 0.0002), than that of the SFC method (%BF SFC), i.e., 30.38 (SD: 4.634), which is 0.68 % higher. The best prediction equation for the %BF by SFC method was [%BF SFC = -26.154 + 0.208 SFss + 0.374 age + 0.354 SFbi + 32.066 WHR] (R² = 84.8), where SFss and SFbi are skin fold thicknesses at subscapular and biceps regions, respectively, measured with SFCs, and that by the US method was [%BF US = 0.713 + 0.351 USsi + 0.232 age + 0.248 USss + 0.448 USbi] (R² = 84.6), where USsi and USss are skinfold measurements at suprailiac and subscapular regions, respectively, measured by US technique.

Conclusion

In our study, we arrived to the conclusion that even though the estimated %BF by both the methods were found to have a significant correlation with each other, the values were very less in case of the US method. In the prediction equations, it was found that the skinfold thickness at the suprailiac region was not found to be the significant determining factor for estimation of %BF by SFC method as that by the US method. Looking at the lesser sample size with all participants being males, we do not recommend the prediction equations to be used in clinical practice in spite of the high R² values.

Thickness of rectus abdominis measured by ultrasound in critically ill patients after abdominal surgery: A retrospective cohort study

BACKGROUND

Early identification of patients at high risk of prolonged mechanical ventilation is important in critical care. Sarcopenia, the loss of muscle mass and function, has been reported to be associated with extended mechanical ventilation and prolonged ICU stay. Although ultrasound is noninvasive and widely used in critical care, there is no standard method of using it to assess sarcopenia.

OBJECTIVES

The study aims to investigate the relationship between outcomes of critically ill patients and the ratio of BMI to the thickness of rectus abdominis measured by a standardised ultrasound examination.

DESIGN

A retrospective cohort study.

SETTING

Surgical ICU of a tertiary referral hospital, from October 2017 to June 2018. The thickness of rectus abdominis (RA) was measured while performing extended focused assessment sonography for trauma. BMI was divided by the thickness of rectus abdominis over the upper abdomen to derive the BMI-RA thickness ratio.

PATIENTS

Sixteen male and 11 female patients admitted to ICU after major abdominal surgery.

MAIN OUTCOME MEASURES

The primary outcome was in-hospital mortality, and the secondary outcomes were durations of mechanical ventilation, ICU stay and hospital stay. The disease severity, serum albumin level and BMI-RA thickness ratio were also analysed.

RESULTS

Ultrasound measurement was easy to perform without adverse effects. The BMI-RA thickness ratio was significantly higher in nonsurvivors and was associated with ICU stay, hospital stay and duration of mechanical ventilation. Multivariable logistic regression showed that the BMI-RA thickness ratio was a predictor of in-hospital mortality.

CONCLUSION

The BMI-RA thickness ratio is related to the outcomes of patients transferred to ICU after major abdominal surgery. Measuring the thickness of rectus abdominis by ultrasound is well tolerated and easy to perform in surgical ICU. Larger prospective studies are required to confirm current findings.

Radiation protection in non-ionizing and ionizing body composition assessment procedures

Body composition assessment (BCA) represents a valid instrument to evaluate nutritional status through the quantification of lean and fat tissue, in healthy subjects and sick patients. According to the clinical indication, body composition (BC) can be assessed by different modalities. To better analyze radiation risks for patients involved, BCA procedures can be divided into two main groups: the first based on the use of ionizing radiation (IR), involving dual energy X-ray absorptiometry (DXA) and computed tomography (CT), and others based on non-ionizing radiation (NIR) [magnetic resonance imaging (MRI)]. Ultrasound (US) techniques using mechanical waves represent a separate group. The purpose of our study was to analyze publications about IR and NIR effects in order to make physicians aware about the risks for patients undergoing medical procedures to assess BCA providing to guide them towards choosing the most suitable method. To this end we reported the biological effects of IR and NIR and their associated risks, with a special regard to the excess risk of death from radio-induced cancer. Furthermore, we reported and compared doses obtained from different IR techniques, giving practical indications on the optimization process. We also summarized current recommendations and limits for techniques employing NIR and US. The authors conclude that IR imaging procedures carry relatively small individual risks that are usually justified by the medical need of patients, especially when the optimization principle is applied. As regards NIR imaging procedures, a few studies have been conducted on interactions between electromagnetic fields involved in MR exam and biological tissue. To date, no clear link exists between MRI or associated magnetic and pulsed radio frequency (RF) fields and subsequent health risks, whereas acute effects such as tissue burns and phosphenes are well-known; as regards the DNA damage and the capability of NIR to break chemical bonds, they are not yet robustly demonstrated. MRI is thus considered to be very safe for BCA as well US procedures.

Body fat percentage assessment by skinfold equation, bioimpedance and densitometry in older adults

Background

Body fat estimation allows measuring changes over time attributed to interventions and treatments in different settings such as hospitals, clinical practice, nursing homes and research. However, only few studies have compared different body fat estimation methods in older adults with inconsistent results. We estimated body fat percentage (%BF) and the level of agreement among dual energy X-ray absorptiometry (DXA), bioelectrical impedance (BIA) and Durnin & Womersley’s skinfold eq. (SF) in older Brazilian adults aged 60 years and older from the Elderly Project Goiânia, Brazil.

Methods

The analytical sample comprised of 132 participants who had DXA data. The level of agreement for the %BF estimated by BIA, SF and DXA i.e. reference method, was examined using Bland and Altman’s and Lin’s plot.

Results

Overall, women had higher body mass index and %BF values measured by all three methods used. BIA and SF equation showed strong concordance to estimate body fat percentage in all participants (CCC = 0.857 and 0.861, respectively) and among women (CCC = 0.788 and 0.726, respectively) when compared to DXA. However, both methods underestimated body fat percentage in women and men with high body fat percentage. A strong level of agreement was observed between DXA and the anthropometric equation developed by Durnin & Womersley in men (CCC = 0.846), while BIA had a moderate concordance (CCC = 0.505) in this group.

Conclusion

The examined methods indicated different body fat estimates. However, the best agreement was observed between DXA and the anthropometric SF equation for men. Future research in older adults should develop new SF equations considering different ethnic groups.