Does Routine Repeat Testing of Critical Values Offer Any Advantage Over Single Testing?

N Context.—Before being communicated to the caregiver, critical laboratory values are verified by repeat testing to ensure their accuracy and to avoid reporting false or erroneous results. Objective.—To determine whether 2 testing runs offered any advantage over a single testing run in ensuring accuracy or in avoiding the reporting of false or erroneous results. Design.—Within the hematology laboratory, 5 tests were selected: hemoglobin level, white blood cell count, platelet count, prothrombin time, and activated partial thromboplastin time. A minimum of 500 consecutive critical laboratory test values were collected retrospec-tively for each test category. The absolute value and the percentage of change between the 2 testing runs for each critical value were calculated and averaged for each test category and then compared with our laboratory’s preset, acceptable tolerance limits for reruns. Results.—The mean results obtained for the absolute value and the percentage of change between the testing runs were 0.08 g/dL (1.4%) for hemoglobin levels, 50 cells/mL (10.2%) for white blood cell counts, 1500 cells/mL (9.9%) for platelet counts, 0.7 seconds (1.4%) for prothrombin time, and 5.1 seconds (4.4%) for activated partial thromboplastin time (all within our laboratory’s acceptable tolerance limits for reruns). The percentage of specimens with an absolute value or a mean percentage of change outside our laboratory’s acceptable tolerance limits for reruns ranged between 0 % and 2.2 % among the test categories. No false or erroneous results were identified between the 2 testing runs in any category. Conclusions.—Routine, repeat testing of critical hemo-globin level, platelet count, white blood cell count, prothrombin time, and activated partial thromboplastin time results did not offer any advantage over a single run. (Arch Pathol Lab Med. 2011;135:440–444) The concept of a critical value as a laboratory result thatreflects a potentially life-threatening emergency was coined by Lundberg in the early 1970s.1 Since then, this concept has been adapted by national and state laboratory accreditation and regulatory agencies, such as the Colleg