It's not you, it's me: time to narrow the gap in weekend care.

To cite: Lapointe-Shaw L, Bell CM. BMJ Qual Saf 2014;23:180–182. Numerous studies have now described the ‘weekend effect’ and its negative impact on timeliness of inpatient care and mortality. Patients presenting with numerous medical and surgical problems experience better outcomes if they happen to arrive in hospital on a workday versus a weekend day. Researchers have highlighted the problem as reflecting reduced staffing and decreased access to specialised services at the weekend. Remarkably, the weekend effect was recently found to extend even to elective admissions and surgeries, raising major questions about resource planning around elective care that occurs near the end of the week. 8 Perez Concha et al analysed administrative data from Australian hospitals between 2000 and 2007. They compared 7-day mortality after hospital admission in patients admitted during the weekend versus a weekday, stratifying their analysis by diagnostic group. They defined the weekend as occurring between midnight on Friday and midnight on Sunday. Their analysis included ORs for death after weekend versus weekday admission, as well as survival curves and HRs. In all, 16 of 430 diagnostic groups showed evidence of a weekend effect for 7-day patient mortality. No conditions demonstrated an ‘inverse weekend effect’, or decreased mortality over the weekend relative to the work week. In addition to risk ratios, the authors present the absolute number of excess deaths for each condition. All together, these conditions account for 21 excess deaths per 1000 patient admissions. Adjustment for differences in case mix between weekend and weekday groups surprisingly increased the magnitude of the observed weekend effect. This finding suggests that patients admitted at the weekend had a lower baseline risk than those admitted during the rest of the week, a result that at first seems counterintuitive. So why would this study report that weekend patients were in fact at lower risk? The authors note that patients admitted at the weekend were younger and had fewer comorbidities. At first blush, this would suggest that weekend patients are inherently at lower risk, and that any excess mortality must result from deficiencies in care. There is, however, another possible explanation. Younger, healthier patients could be more acutely ill. Younger patients with fewer comorbid conditions are more likely to be employed. Employed patients might delay seeking medical care during the work week only to present at the weekend in worse condition. Severity of presenting illness is a major determinant of prognosis, yet it does not factor into risk adjustment based on administrative data. As in most other studies of the weekend effect, risk adjustment is limited to readily available information such as age and comorbidities. These adjustments account for neither severity of disease nor patient functional status. Weekend patients, while appearing to be at lower risk, may in fact be sicker in ways not captured using administrative data. Adjusting for comorbidities and age will only make this group’s outcomes appear worse relative to their older, more chronically ill weekday counterparts. If baseline risk adjustment is limited, teasing out whether care or characteristics are driving excess risk is challenging. Fortunately, the authors found an alternative way to distinguish patient and care effects. The main contribution of the study by Perez Concha et al is the novel use of excess risk over time curves to identify which conditions exhibit time trends most suggestive of a weekend effect. These were generated by subtracting the medical condition-specific mortality risk curves for weekday patients from those generated for weekend patients. For each admitting diagnosis, these EDITORIAL