Exploring the Alternative Method in Estimation of Actual Body Weight by Knee Height and Mid-Arm Circumference in Chinese Population by Evidence Based Approach

Abstract Description

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Authors (including presenting author) :

Chung TK (1), Tong CM (1), Lo YPS (1), Lo WK (2), Hui WLG (3), Ho PYB (4)

Affiliation :

(1) Central Nursing Division PWH, (2) A&E PWH, (3) Private Ward Unit PWH, (4) Central Nursing Division NTEC

Introduction :

Body weight is a significant parameter for health care workers to review patients’ nutritional status and use for doctor’s medication dosage prescription. However, there are some reasons that they couldn’t obtain the data due to patients’ critically ill condition or severe pain, therefore, a convenient alternative method should be explored to estimate patients’ body weight. In 2017, a study was conducted in Prince of Wales Hospital (PWH) to assess the possibility of knee-height and mid-arm circumference in estimating patient’s body weight.

Objectives :

The objectives of this study were to validate the use of Ross Laboratories equations in Hong Kong, and to develop ethnic-specific regression models for body weight estimation.

Methodology :

This was a correlational study with adult patients randomly recruited. After gaining their consent, the measurements were performed by trained data collectors. Inter-rater reliability was performed to test the variation among data collectors about the measuring techniques. The deviation rate for each data collector from the mean was maintained within 5% error.

Result & Outcome :

There were 644 subjects recruited. When their measurements were put into Ross’s equation, estimated body weight of each subject was calculated. After comparing the estimated body weight with the actual figure, 11-22% of subjects were found having more than 15% error. By putting knee height, mid-arm circumference and age as independent variables and actual body weight as dependent variable in multiple linear regression model, four new equations were derived. Power analysis for these equations could achieve nearly 100%. After comparing the estimated body weight with the actual figure, only 9-14% of subjects were found more than 15% error; which were much less than those by using Ross’s equations. New equations were planned to be rolled out to other NTEC hospitals. A survey showed that 72.8% & 74% of nurses strongly agreed the method was simple and useful respectively. Conclusion The study has supported that knee height, mid-arm circumference and age are useful and feasible factors for estimating body weight. The new equations devised from this study are important for improving accuracy in body weight estimation.