• Healthcare quality improvement
• Quality improvement
• Quality measurement

Since the publication of the influential paper by Bell and Redelmeier in 2001,1 the ‘weekend effect’, whereby patients admitted to hospital over the weekend experience worse outcomes compared with apparently similar patients admitted during weekdays, has been explored in at least 105 studies.2–6 In this issue, Ruiz et al7 document such an effect across four countries (Australia, England, Netherlands, and the USA) that contribute to the Global Comparators Project8 where electronic summary data are combined across borders. Twenty-eight metropolitan city hospitals contributed data from nearly 3 million admissions. The ubiquitous weekend effect is replicated yet again among emergency admissions in all four countries for hospital mortality measured at 7 days and, except for Australia, at 30 days. For elective surgical procedures, a weekend effect on mortality was observed in all four countries and additionally a ‘Friday effect’ was seen in Dutch hospitals included in the study. The findings are interesting, but should we all rush to Australia to see how acute medical services should be organised so as to avoid a high 30-day mortality rate associated with emergency admissions?

Hospitals included in this study constitute only a very small proportion of all hospitals in respective countries. The data are unlikely to be representative and consequently drawing any conclusion with regard to international comparison could be misleading. The existence of weekend mortality effects within 7 days following admission has been demonstrated previously in a larger study covering >500 hospitals in Australia.9 Failure to confirm the 7-day weekend mortality hike at 30 days in the current study can plausibly be ascribed to a diminished signal-to-noise ratio; as time passes new and recurrent illness supervenes, diluting any effect from the …