The paper by Burch et al1 on the modified early warning (MEW) score predicting hospital admission and inhospital mortality is both interesting and topical.

I agree with the authors that the MEW score, a risk assessment tool now widely used in UK emergency departments (ED) to facilitate the early identification of high-risk patients, is a good predictor of inhospital mortality.2 I also share the authors’ concerns that there are limitations to using the MEW score and that the MEW score needs to be interpreted in context with other clinical findings associated with a risk of adverse outcome. This is supported by our findings among adult ED patients admitted to hospital, in whom 33% of non-survivors were found to have low ED arrival MEW scores (0–2).

However, I have some concerns regarding the methodology of the described study. It is not clear when the physiological parameters to calculate the MEW score were taken, whether on arrival, before discharge/admission, or whether the worst ever recorded measurement had been used? Not knowing how the MEW score was determined in this cohort affects its practical application.

The authors only included data from 70% of the expected cohort in their analysis. There may be various reasons for data being missing, some of which would have had very little impact on the final results of the study, other missing data, however, and this is my prime concern, could have seriously introduced bias and invalidated the findings.3

The authors conclude that the study has shown that the MEW score can identify patients at increased risk of inhospital mortality. However, I am concerned that this statement may be misleading as, although statistically true, a difference of less than 1 in the mean MEW score between survivors and non-survivors is barely clinically meaningful and would be unlikely to be of any help in identifying potential non-survivors. It is well accepted that patients with high MEW scores are more likely than those with low MEW scores to have an adverse outcome, but “high” and “low” are not well defined. For an assessment tool to assist in clinical decision-making, there is a need for cut-off points to be identified that trigger a precise action, such as hospital admission or intensive care unit review. Identifying MEW score cut-off points for “ruling out/in” using sensitivity or specificity would have been a better indicator of the clinical usefulness of the MEW score.