Introduction Weight is a vital component of a patient's medical information which is used in a number of assessments such as the Malnutrition Universal Screening Tool (MUST), calculating drug dosages and monitoring medical treatments. The purpose of this audit was to determine the accuracy of hospital weighing scales in accordance with the UK Weighing Federation, and investigate the impact of inaccurate weights on medical assessments.
Methods Newly calibrated scales were used to obtain a reference weight for four subjects with a range of weights: subject A 31.8 kg, subject B 54.6 kg, subject C 60.8kg and subject D 106.7 kg. The subjects were then weighed on all functioning hoist, chair and standing (class 3) weighing scales within the Conquest Hospital, a medium size district general hospital. The collected weights were compared to the reference weight, and then the differences compared to error allowance specified by the UK Weighing Federation for Class ІІІ scales.
Results A total of 33 scales were included in the study including one set of standing scales which produced an excessive inaccuracy. Good results were obtained with the average weight subject (60.8 kg) with the chair and standing scales weighing within UK Weighing Federation error allowance by 82% and 67%, respectively. Accuracy decreased as the weight increased as can be seen in the Abstract PMO-035 table 1. Results for subject A (31.8 kg) did not meet the UK Weighing Federation standards. However, at least 78% of the results from the chair and standing scales weighed within 500 g of all the subjects' reference weights. The largest error on the hoist scales for Subject B (54.6 kg) was +5.4 kg increasing body mass index (BMI) by 2.0 kg/m2 (height-1.64 m). A patient of similar height with a BMI of 18 kg/m2 would calculate as a BMI of 20 kg/m2. The MUST score would be 0 instead of 2, which triggers a referral for dietetic assessment according to Trust policy.
Conclusion This scales audit identified that both chair and standing scales were the most accurate over the range measure 60 kg and 105 kg. The hoist scales were the most inaccurate. The accuracy of all the scales decreased with the heaviest subject. With increasing levels of obesity this audit highlighted the need to calibrate scales more often and to re-audit with a wider weight range of up to 200 kg.
Competing interests None declared.