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One in three hospital scales is inaccurate, LACORS study finds

3 November 2008

A third of all hospital scales tested by council trading standards officers as part of LACORS' nationwide study of NHS weighing equipment were found to be inaccurate and could be putting patients’ health at risk.

Officers also uncovered a lack of basic training for hospital staff in using weighing equipment, widespread use of household bathroom scales which are not suitable for medical use and poor procedures for testing the accuracy of scales.

Between April and August, council trading standards teams inspected around 8,000 individual sets of scales in more than 200 hospitals across the UK as part of the National Medical Weighing Project, making sure they are accurate, legal and fit for purpose. Oncology and paediatrics departments have been targeted in particular.

Key findings:

  • One-third (34%) of all the equipment tested was inaccurate.
  • Only one in six (16%) hospitals trained staff in basic use of weighing equipment.
  • One in five (22%) scales were not set to zero.
  • Four out of ten (40%) scales were Class IV, which are not recommended for medical use as the scale divisions are too great, leading to imprecise measurement.
  • Three-quarters (76%) of hospitals maintained an inventory of their weighing equipment – however many were not kept up-to-date.
  • Two-thirds (67%) of hospitals had a consistent inspection regime for their equipment.
  • Four out of ten (40%) scales were switchable between metric and imperial, which can lead to readings being taken in imperial which are assumed to be metric. Such confusion was responsible for the $125m failure of the Mars Climate Orbiter spacecraft. More than 300 scales were set to imperial during inspections.

The National Medical Weighing Project was set up by LACORS after a series of pilot studies in 2007 found hospital staff using inaccurate or unsuitable scales to calculate dosages of medication for patients, including small children.

In one case a four-year-old cancer patient was weighed using ordinary bathroom scales so staff could work out how much radiation should be administered as part of her treatment. The scales wrongly indicated that the girl had gained weight during the day despite not having eaten and suffering from suspected dehydration. This discrepancy could have led to the girl being given a potentially harmful dose of radiation treatment.

As a result of the project’s findings, LACORS has come up with a six-point plan to help NHS trusts to improve patient care, save money and protect against legal claims:

  • One department in each hospital or trust should be responsible for buying and maintaining all its medical weighing equipment.
  • Each trust should regularly test weighing equipment to make sure it is accurate.
  • All staff should received basic training for the use of weighing equipment.
  • Any equipment that is found to be inaccurate should be immediately removed from service
  • While some Class IV (i.e. bathroom) scales may be suitable for some medical purposes, we recommend that all new medical weighing equipment ordered should be of accuracy Class III (or higher if appropriate).
  • From now on, scales purchased for medical purposes should only be capable of metric display. Trusts should be aware of the pitfalls of using switchable scales and may wish to consider replacing them, or having the switches removed. Conversion charts can be provided for those patients who wish to know their weight in imperial.

Trading standards officers who took part in inspections reported overwhelming support for this project from NHS staff and trusts and there was nothing to suggest that the problems found were the result of anything other than a lack of awareness of the issues.

During the remainder of the current financial year, council trading standards services will be working with hospitals to help deliver these improvements. There will be a repeat inspection in spring 2009 to monitor progress and offer further advice, following which a final report will be produced on the change that the project has helped bring about.

Cllr Geoffrey Theobald OBE, Chairman of LACORS, said:

“An inaccurate petrol pump or supermarket scales isn’t exactly a matter of life or death but getting accurate, consistent weight reading for a hospital patient could be. When you consider why a patients would be weighed - to calculate dosage for medication, anaesthetic or even radiation – you realise the importance of getting this weight right.

“According to the results of the National Medical Weighing Project, one-third of all hospital scales are inaccurate. Some of these inaccuracies could be tiny and have little effect on patient care, for example when monitoring adult obesity. However, when weighing a premature baby to calculate medication, pinpoint accuracy is crucial.

“Council trading standards teams taking part in the project have focused on making sure that hospital staff have the information and guidance they need to maintain the highest standards of accuracy. The commitment of NHS staff is well known. This project is not about naming and shaming hospitals that are found to have problems, it is about councils and their local hospitals working together for everyone’s benefit.

“We hope the NHS will work with trusts nationally to ensure that the necessary changes are made to help safeguard patient care.”

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