eDrugCalc: an online self-assessment package to enhance medical students' drug dose calculation skills

Daniel S. McQueen, Michael J. Begg, Simon R. J. Maxwell

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

center dot Dose calculation errors are an important cause of some of the most serious medication incidents in advanced healthcare systems.

center dot A number of small studies have shown that dose calculations are poorly performed by hospital doctors, nurses and medical students.


center dot The performance of dose calculations was highly variable amongst a large cohort of medical students from a leading UK medical school.

center dot Calculations that involved converting concentrations expressed as percentage or calculating infusion rates were identified as major weaknesses.

center dot The availability of an online self-assessment and education package, coupled with encouragement and twice-yearly formative assessment, led to a significant improvement in performance.


Dose calculation errors can cause serious life-threatening clinical incidents. We designed eDrugCalc as an online self-assessment tool to develop and evaluate calculation skills among medical students.


We undertook a prospective uncontrolled study involving 1727 medical students in years 1-5 at the University of Edinburgh. Students had continuous access to eDrugCalc and were encouraged to practise. Voluntary self-assessment was undertaken by answering the 20 questions on six occasions over 30 months. Questions remained fixed but numerical variables changed so each visit required a fresh calculation. Feedback was provided following each answer.


Final-year students had a significantly higher mean score in test 6 compared with test 1 [16.6, 95% confidence interval (CI) 16.2, 17.0 vs. 12.6, 95% CI 11.9, 13.4; n = 173, P < 0.0001 Wilcoxon matched pairs test] and made a median of three vs. seven errors. Performance was highly variable in all tests with 2.7% of final-year students scoring < 10/20 in test 6. Graduating students in 2009 (30 months' exposure) achieved significantly better scores than those in 2007 (only 6 months): mean 16.5, 95% CI 16.0, 17.0, n = 184 vs. 15.1, 95% CI 14.5, 15.6, n = 187; P < 0.0001, Mann-Whitney test. Calculations based on percentage concentrations and infusion rates were poorly performed. Feedback showed that eDrugCalc increased confidence in calculating doses and was highly rated as a learning tool.


Medical student performance of dose calculations improved significantly after repeated exposure to an online formative dose-calculation package and encouragement to develop their numeracy. Further research is required to establish whether eDrugCalc reduces calculation errors made in clinical practice.

Original languageEnglish
Pages (from-to)492-499
Number of pages8
JournalBritish Journal of Clinical Pharmacology
Issue number4
Publication statusPublished - Oct 2010


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