Table 2.

Comparison of the ability to affect care for critical INR results communicated during clinical hours and after hours

OUTCOMETIMING OF INR RESULT NOTIFICATION
DURING CLINIC HOURSAFTER HOURS
Notification of result led to same-day care, n/N (%)*
  • All critical INR results174/200 (87.0)101/200 (50.5)
  • Only first critical INR result assessed per patient108/128 (84.4)72/148 (48.6)
  • Excluding patients taking warfarin in the morning and those for whom timing was unknown162/171 (94.7)94/164 (57.3)
Same-day care implemented, n/N (%)
  • Hold warfarin153/174 (87.9)80/101 (79.2)
  • Reduce warfarin dose16/174 (9.2)17/101 (16.8)
  • Administer oral vitamin K21/174 (12.1)6/101 (5.9)
  • Refer to health care provider or ED3/174 (1.7)1/101 (1.0)
Notification of result led to same-day care based on severity of INR, n/N (%)
  • INR 5.1–9.0161/186 (86.6)94/189 (49.7)
  • INR > 9.013/14 (92.9)7/11 (63.6)
Incidence of thromboembolism, n/N (%)1/200 (0.5)1/200 (0.5)
Incidence of bleeding, n/N (%)4/200 (2.0)6/200 (3.0)
  • ED—emergency department, INR—international normalized ratio.

  • * The differences between after-hours notification and notification during clinic hours are significant (P < .001).

  • More than 1 strategy to alter care is possible, except both holding and reducing warfarin.

  • Includes 7 critical INR results without event-related outcomes for 30 d either owing to transfer of care to patients’ general practitioners or warfarin discontinuation.