Table 1

Patient outcomes associated with nurse staffing*

AuthorCountryDesignNo of EDsComparisonsOutcomeKey resultsPatients seen (census)Internal validityExternal validity
Brown et al11USARetrospective Observational1Actual compared with scheduled RN staffing hoursLeft without being seenRNs staffing predictor of a higher number of patients leaving without being seen50 000
Chan et al14USAProspective Observational2Mandated nurse-patient ratios compared with out-of-ratio careTime to antibiotic administrationShorter time to antibiotic administration if nurse staff in ratio61 000+
Chan et al10USAProspective Observational2Mandated nurse-patient ratios compared with out-of-ratio careWaiting time
Emergency department care time
Longer wait times when the ED overall was out-of-ratio.
Longer ED care time for patients whose nurse was out-of-ratio.
59 733+
Daniel15CanRetrospective Observational107Nurse-patient ratiosPatient satisfactionIncrease in overall patient satisfaction associated with nurse staff skill mix. Per cent of full-time nursing worked hours negatively associated with overall patient satisfaction. Physician and nurse courtesy highly associated with patient satisfaction.182 022++
Greci et al13USACross-sectional1Staff workload when the ED was crowded and not crowdedLeft without being seen
Ambulance diversion
RN:patient ratio significantly associated with patient leaving without being seen
No association with ambulance diversion
RN:patient ratio significantly associated with perception of crowding
30 000
Hoxhaj et al12USARetrospective Observational1Nurse staffing levelsLeft without being treatedNo. of nursing vacancies (FTE) strongly correlated with percentage of patients who left without being treated
Total monthly nursing hours to monthly ED census ratio strongly correlated with percentage of patients who left without being treated
92 000
Rathlev et al16USATime series1Number of ED nurses on duty
Hospital occupancy
Number of patients admitted to the hospital
Number of patients admitted from ED to ICU
Number of ED resuscitation cases
Length of stay (LOS)Numbers of nurses, ED discharges on previous shift, resuscitation cases, and elective surgical admissions not associated with LOS on any shift.
LOS reduced per additional nurse (average staff level unclear)
91 643+
Schull et al17CanRetrospective Observational1Number of patients boarded in the ED
Number of ED nurse hours worked per shift
Number of emergency physicians per shift
Ambulance diversionNumber of admitted patients boarded in the ED predictor of increased ambulance diversionED nurse hours not associated with crowding37 999
Weichenthal and Hendey9USABefore and after1Nurse-patient ratiosWaiting times, Left without being seen, Medication errorsTime to aspirin administrationTime to antibiotic administrationAfter the introduction of nursing ratios
▸ wait times increased significantly
▸ Percentage of patients who left without being seen decreased
▸ No significant change in reported medication errors after the implementation of nursing ratios
▸ No significant change in the rate of aspirin administration.
▸ For patients with pneumonia, decrease time from written order to administration of antibiotics 
59 163 (before)
55 976 (after)
  • *Internal/external validity (+, −). The summary bias assessment was completed from a detailed evaluation that considered risk adjustment, data completion and sampling strategy across data sources, outcome types and levels. Ratings were summarised to give a + for some of the assessment criteria fulfilled and conclusions unlikely to change or − for few criteria fulfilled and conclusions likely to change. During quality assessment, no studies were rated ++ indicating that the method was likely to minimise bias or with conclusions unlikely to change.

  • ED, emergency department.