Critical values comparison: a College of American Pathologists Q-Probes survey of 163 clinical laboratories

Critical laboratory values are values that may be indicative of life-threatening conditions requiring rapid clinical intervention. Designation of critical values by clinical laboratories is required by the Clinical Laboratory Improvement Amendments and regulatory agencies. The development of critical values often involves consultation with clinical services. Also, questions are frequently asked about how critical values compare between institutions.

To examine and compare critical value ranges for selected common critical value analytes. Additional specific questions addressed the source of these values, the inclusion of specific items on a critical values list, and the procedures for establishing such lists.

A total of 163 clinical laboratories provided critical values for potassium, calcium, magnesium, thyroid-stimulating hormone, hemoglobin, platelet count, and activated partial thromboplastin time. Collected data were subjected to analysis for statistical variation. A questionnaire regarding demographic characteristics, institutional practices, and critical values management was also completed by participants.

There was slight variation in pediatric and adult critical values used by the central 80% of study laboratories. Three areas of interest were noted: (1) 27% of laboratories allowed nonpractitioners to accept inpatient critical value reports, (2) there was nonconsensus regarding the handling of outpatient critical values during weekday versus evening/weekend hours, and (3) only 56% of respondents had a written critical values policy or procedure.

Pediatric and adult critical values for the selected analytes were consistent in a comparison between the 163 clinical laboratories. Several weaknesses in current critical values management were identified. A consensus critical values list that may be of value to other institutions was assembled.