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Author Interview: Dr. Yasushi Ohashi MD

Toho Univ. Nephrology, Tokyo, Japan

Assessment of Body Composition Using Dry Mass Index and Ratio of Total Body Water to Estimated Volume Based on Bioelectrical Impedance Analysis in Chronic Kidney Disease Patients

Yasushi Ohashi, Takatoshi Otani, Reibin Tai, Yoshihide Tanaka, Ken Sakai, Atsushi Aikawa
Journal of Renal Nutrition - 12 March 2012 (10.1053/j.jrn.2011.12.006)  

Study purpose

Adequate assessment of fluid and nutritional status is of major importance in monitoring chronic kidney disease (CKD) patients. Body mass index (BMI) and Lean body mass (LBM) are proposed as an acceptable nutritional assessment tools.

However, changes in BMI in chronic kidney disease (CKD) patients are affected not only by muscle and fat, but also by fluid volume. To solve the issue, a ratio of extracellular water (ECWBIA) to total body water (TBWBIA) in multifrequency bioelectrical impedance analysis (MF-BIA) has been commonly used for assessing edematous status.

However, this assumption have latent connotation that intracellular water (ICWBIA) is substantially unaffected by changes in fluid volume. Neverthless, the balanc e of ECW and ICW appears to change depending on not only edematous status but the body type (endomorph and ectomorph). 

Therefore, we suggested the novel markers for assessing fluid status and physique index.

What are the main findings of the study?

A combination of DMI, BMI, and TBWBIA/TBWwatson makes it possible to include assessment of fluid volume to the physique index. In addition, ECWBIA/TBWBIA is not a reliable marker of edematous state in CKD patients.

Were any of the findings unexpected?

We propose DMI rather than BMI to be used during assessment of nutritional status in CKD patients. BMI has long been one of the most popular and acceptable nutritional markers.

However, as body weight changes due to fluctuations in fluid status, BMI also changes and hence, cannot be used as an accurate nutritional marker. DMI excludes the factor of fluid volume status and therefore is a more suitable nutritional marker. However, in this study, only a few patients fell into the difference range. Classification of BMI and DMI were too wide to assess changes in fluid volume.

Therefore, the relationship between DMI and BMI is more important than these actual values. A shift in the relationship between DMI and BMI mainly indicates hypovolema or hypervolema. 

What should clinicians and patients take away from this study?

The range for the euvolemic state determined by the TBWBIA/TBWwatson ratio was 0.970–1.029. However, this assertion lacks satisfactory evidence at present.

Moreover, interpretation of the TBWBIA/TBWwatson ratio should be made with caution because of gender differences in standard deviation using the Watson formula (3.76 in males and 3.60 in females).

The reference range of the DMI should be further studied in catamnestic assessments.

What recommendations do you have for future studies as a result of your study?

A combination of DMI and BMI could help in the assessment of body composition in case of changes in body weight.

Moreover, the TBWBIA/TBWwatson ratio can be used for assessing fluid volume status in CKD patients.

These methods make it possible to include fluid volume status to the physique index.

This information is useful to patients and those who provide them with nutritional guidance.

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