Table 2

OR for an adverse event (with 95% CI) for four types of patient safety incidents and for patient mortality, according to NWL measurement by the RAFAELA system (OPC/nurse) and the standard NWL measurement system (patients/nurse), unadjusted and adjusted estimates

IncidentPatient affectedHarm to patient>1 incidentDeath
OPC/nurse, unadjusted model
 Below optimum0.67 (0.58–0.78)0.68 (0.56–0.82)0.66 (0.50–0.88)0.67 (0.47–0.95)0.55 (0.43–0.70)
 At optimum11111
 Above optimum1.28 (1.13–1.45)1.13 (0.96–1.32)1.16 (0.93–1.45)1.25 (0.95–1.66)1.42 (1.19–1.69)
 −2 log likelihood8577.56169.33523.02406.44958.6
 Akaike information criterion8561.56173.33527.02410.44962.6
 Nagelkerke’s R2 0.01060.00560.00520.00560.0160
OPC/nurse, adjusted model
 Below optimum0.79 (0.67–0.93)0.78 (0.64–0.96)0.85 (0.63–1.14)0.73 (0.50–1.07)0.78 (0.60–1.00)
 At optimum11111
 Above optimum1.24 (1.08–1.42)1.08 (0.91–1.28)1.11 (0.88–1.41)1.32 (0.98–1.79)1.43 (1.18–1.73)
 −2 log likelihood8010.85856.33211.12187.94286.5
 Akaike information criterion8106.85952.33307.12283.94382.5
 Nagelkerke’s R2 0.09600.06880.10500.10410.1733
Patients/nurse, unadjusted model
 First group0.74 (0.64–0.86)0.85 (0.71–1.02)0.79 (0.61–1.04)0.80 (0.58–1.10)0.47 (0.38–0.58)
 Second group11111
 Third group1.09 (0.95–1.25)1.18 (0.99–1.41)1.24 (0.96–1.58)0.95 (0.70–1.30)0.97 (0.81–1.17)
 −2 log likelihood8589.16180.93525.12416.54958.8
 Akaike information criterion8593.16184.93529.12420.54962.8
 Nagelkerke’s R2 0.00550.00330.00450.00100.0159
Patients/nurse, adjusted model
 First group0.89 (0.75–1.05)0.98 (0.80–1.21)0.90 (0.66–1.23)1.01 (0.71–1.44)0.86 (0.68–1.08)
 Second group11111
 Third group1.13 (0.96–1.33)1.15 (0.94–1.41)1.03 (0.77–1.39)1.15 (0.81–1.64)1.20 (0.97–1.49)
 −2 log likelihood8029.85863.13213.42196.14301.8
 Akaike information criterion8.125.85959.13309.42292.14397.8
 Nagelkerke’s R2 0.09310.06740.10430.10040.1698
 Number of events1367848400246636
  • The table summarises results from 20 different models estimated on 12 475 calendar days, representing 36 wards at 4 hospital units.

  • Adjusted model refers to models adjusted for ward-specific effects and effects of the of the week, holiday and season.

  • Estimates for ward-specific effects and effects of day of the week, holiday and season are found in the online supplementary electronic files.

  • At optimum refers to the assumed optimal nursing intensity point with ±15% deviation, as defined by the RAFAELA system.

  • Patients/nurse refer to a categorisation into three equally large groups.

  • Categories used for day of the week are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday.

  • Categories used for holiday are No or Yes, where Yes refers to Easter, Midsummer, Christmas and New Year.

  • Categories used for season are January–March, April–May, June–August, September–October and November–December.

  • NWL, nursing workload; OPC, Oulu Patient Classification.