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Practice comment

Poor numeracy skills must be tackled to cut medication errors


Drug errors related to the wrong dose are a leading cause of serious incidents. Trusts must implement strategies to ensure staff are competent to calculate doses, says Paul Warburton

The NHS next stage review said improving patient safety should be at the top of the healthcare agenda for the 21st century.  However, medication errors are still far too common, even though they are largely preventable.

While drug calculation errors occur for a number of reasons in the clinical environment, the poor numeracy skills of clinical staff can be identified and addressed. Training and education for all healthcare professionals is designed to ensure that when they qualify they are competent in their roles and care delivery. Following qualification, it is a requirement for all registered practitioners to remain competent and up to date in their practice.

It is reasonable for patients to expect that each healthcare professional involved in delivering their care is competent in the skills required to perform their role safely. For those involved in prescribing or administering medicines this includes the ability to calculate drug doses safely and accurately.

However, errors in medication delivery due to administering the wrong dose are a common cause of patient safety incidents reported to the National Patient Safety Agency’s National Reporting and Learning Service and a leading cause of serious incidents. In paediatrics, almost half of the medication errors reported are related to the wrong or unclear dose or strength of medicine (NPSA, 2009).  

All healthcare professionals delivering patient care must be competent in calculation; it is an essential skill for safe medicines administration. However, problems with numeracy among healthcare professionals are well documented and reports to the NPSA NRLS show that calculation errors continue to result in medication errors and patient harm (NPSA, 2009). In addition to the huge personal cost to the individuals involved, medication errors cause a significant financial cost to the NHS; this was estimated to be more than £750 million in England per year (NPSA, 2007).

In spite of the acknowledged importance of numeracy skills in delivering a range of clinical tasks, including accurate drug calculation, it is currently possible and common practice for healthcare professionals to progress through their career without ever having their numeracy skills assessed after qualifying. In view of the continued incidence of medication errors due to incorrect drug calculations and the subsequent patient harm, healthcare organisations should implement strategies to address this important patient safety issue.

From April 2010 it will be compulsory rather than voluntary for NHS organisations to report safety incidents to the NRLS (E-Health Insider, 2009). This will undoubtedly lead to an increase in the number of reported medication errors, including those caused by incorrect dose calculations. It is likely that this will also result in an increase in public awareness of this issue. 

All healthcare organisations should implement strategies that help to identify their clinical staff’s numeracy skills, improve awareness of the importance of competence in calculation and minimise the risk of drug calculation errors. They should also ensure routine and regular assessment of all clinical staff’s numeracy skills to reduce the risk of calculation errors. This should be an accepted part of continuing professional development and annual clinical update among healthcare professionals.

Such strategies will lead to increased awareness of the importance of numeracy, improved quality of care for patients and a reduced risk of medication errors due to poor numeracy.

PAUL WARBURTON is senior lecturer, Faculty of Health, Edge Hill University, Lancashire



Readers' comments (7)

  • As a lecturer in access to nursing courses as well as nursing diploma this is a topic that is discussed every year. We have intermediate 2 core skill numeracy built into the course, but students consistently question what numeracy has to do with nursing. They cannot pass the access course without numeracy but still universities will accept my students based on their other qualifications (even if they have failed numeracy). I feel very strongly that all universities should set a minimum level of core skill numeracy that would demonstrate competence prior to entry. Whilst there are other reasons besides numeracy competence that cause drug calculation errors, this would be a sensible place to start.

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  • Philip D Marini
    MSc., Cert Ed., Dip Ed., ACP., FCollT
    Numeracy Skills Support - Learning and Development Dept BSUH NHS Trust

    My studies of the relationship between numeracy skills and drug administration errors do not support or reflect the need for the regular lambasting of nurses through similar articles.

    There is often much mis-interpretation of the statistics relating to drug administration errors with inferred poor nurses' numeracy skills being are the prime cause. Yes, there will always be some nurses who need support and confidence building, but often blanket criticism seems to be prevalent and unnecessary.

    Rights of Time, Patient, Drug and Route are often included amongst statistics with the Right of Dose which is the numeracy-related area being criticised.

    I regularly run sessions for newly-appointed nurses, within BSUH NHS trust, who have to undergo required drug administration tests (pass mark 100%). So infact, nurses do actually have some on-going assessments post-qualification.

    Feedback from these sessions, together with my literature research, indicate that many of the criticisms of nurses' numeracy skills are not supported in fact. The testing of these skills is carried out isolation via sometimes poorly-written papers, and areas tested are often not relevant to the actual tasks which they are required to carry out.

    The contect of many Trusts' tests often focus on fractions, percentages and decimal manipulation and conversion, rather than further understanding and confidence-building in actually calculation accurate drug administration amounts.

    My literature searches, and review of much written about nurses' alleged poor numeracy skills, reflect recent research by Kerri Wright (*some of her brilliant work listed below) where she looked at related 33 articles. It is interesting that no studies were found which examined nurses' drug calculation errors in practice. She notes that,"...The review found insufficient evidence to suggest that medication errors are caused by nurses' poor calculation skills. Of the 33 studies reviewed, only 5 articles specifically recorded information relating to calculation errors and only two of these detected errors using the direct observatonal approch". (Nurse Education Today - 15th June 2009).

    I accept that nurses' numeracy skills should be appropriate to the tasks required to be undertaken and I do not diminish the importance of the Right Dose. However, I feel that many of these articles which criticise nurses' numeracy skills, without much substance, are not helpful to promoting professionalism and support in nurses and confidence amongst the public.


    Wright, Kerri - Senior Lecturer Department of Acute and Continuing Care, Greenwich University. ‘Resources to Help Solve Drug Calculation Problems’. 2009

    ‘The Assessment and Development of Drug Calculation Skills in Nurse Education – A Critical Debate’. 2009..

    ‘Using a Mathematical Problem Solving Model as a Framework to Support the Development of Calculating Skills’. 2009

    ‘Do Calculation Errors by Nurses Cause Medication Errors in Practice?’. 15/06/2009.

    ‘A Written Assessment is an Invalid Test of Numeracy Skills’. March 2007

    ‘Drug Calculation Skills – Developing a repertoire of Methods for Solving Drug Calculations’. 2009

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  • Article dated 10-Mar-2010 10:52 am was submitted by Philip D Marini as indicated in text and not Shaun Marten. Apologies for this error.

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  • The article refers to Healthcare Professionals and registered staff; this I take to include but not restricted to Registerd Nurses, but would also encompass Dieticians, State Registered Paramedics and not forgetting Medical Practitioners. All medical staff should similarly have their numeracy assessed.

    Because someone has a scientific/medical degree doesn't mean that they are necessarily numerate, bear in mind that some of the greatest scientific minds in the National Aeronautics and Space Administration (NASA) in the US made a fundamental error by mixing SI units and imperial units.

    Numerical errors in computer software resulted in people being exposed to potentially lethal levels of 'therapeutic' radiation in Canada.

    I consider myself numerate having studied maths to degree level and having been involved in designing computer software for a variety of systems including those that could be considered safety critical; I am quite adept at mental arithmetic in various number systems including binary, octal, hexadecimal, base 14 as well as base 10; I am fairly adept at converting between SI weights and Imperial weights, also in my head; yet I failed to get 100% on my recent arithmetic test because I made a simple error when writing down the calculation. The reason for disallowing the use of calculators on the grounds that you could make a mistake inserting the numbers does not stand up to scrutiny; it is just as easy to make a transposition error when writing down a calculation, which is what I did, and I repeated the error when checking it.

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  • when i began my nurse training only 12 months ago my universtiy never questioned my ability in maths, only my level of literacy and if i had a level 3 qualification. I am now struggling with nursing calculations and a and p. I feel all students should be more prepared by universtiys for what will be expected from them as a registered nurse and more support should be available to mature students.

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  • I also feel that there should be some basic standard of literacy - it is depressing how many trained nurses cannot spell or even produce a properly constructed sentence. We are constantly being told our nursing records are to be viewed as legal documents, and that good communication is vital, but I have seen many which appear barely literate - or am I just old-fashioned?

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  • Being dyslexic means that i sometimes find spelling difficult however my documentation is always written clearly which is something that most doctors find difficult to do!

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