Quality indicators for critical international normalized ratio measurements in a hemostatic laboratory

•Critical INR threshold is usually 5.0 but a wide range of 2.6 to 10.0 has been observed.•There were 0.6% critical INR results of which 94% remained critical on repetition.•Loss of sample integrity during transport was responsible for spuriously raised INR.•We observed poor communication for notifying critical INR results.

ObjectiveThis study aimed at reviewing the quality indicators for reporting critical international normalized ratio (INR) in a coagulation laboratory.Design and methodsThis is a retrospective study conducted at Aga Khan University Hospital, hemostatic laboratory from February 2010 till January 2011. Critical INR was defined as ≥ 5.0. All critical INRs were rechecked and results were communicated to the doctor or patient. Two quality indicators monitored were % of results communicated to the patient/doctor and % of results that remained critical after re-testing.ResultsDuring the study period, a total of 59,980 INRs were reported. Of these 376 or 0.6% were critical. Successful communication of critical results to the doctor or patient was achieved in 275/376 (73.1%). Overall 353 or 94% (343 initial and 10 re-draw) samples had critical INR on repetition. Twenty five patients of the 240 warfarinized patients with critical INR had mild bleeding. No life threatening bleeding was observed in any patient.ConclusionWe observed poor communication for notifying critical INR results during the study period. Routine repeat analysis of critical INR did not alter results in majority of samples. The study assisted in improving communication in subsequent years. Further work is needed to establish evidence based upper and lower cutoff of critical INR. Effect of replicate analysis on turnaround time and accuracy of results needs evaluation.