Critical limits (alert values) for physician notification: universal or medical center specific limits?
The concept of critical limits (alert values), defined as an imminent life threatening laboratory result requiring immediate physician notification, has been widely adopted as a standard of good laboratory practice. Although virtually all laboratories have tests with critical limits, surveys have shown that there is no universal alert value list. Recently, nine VA medical centers in the New England region, which now constitute one consolidated entity, were surveyed with the objective of summarizing critical limits. Universal (100 percent) critical limit tests for clinical chemistry were: Calcium; mean low/high, 6.5/12.4 mg/dL: Glucose 48/432 mg/dL: Potassium 2.8/6.1 mmol/L: Sodium 121/159 mmol/L. Universal hematology tests included: Hematocrit 22.2/59.7 percent: Platelet count 61K/983K: white blood count 1.9K/29K. Although there was universal agreement that abnormal coagulation tests (PT, PTT) should be included on the hematology critical limit list, there was wide variation in the reporting of coagulation tests (seconds and INR) and patient therapeutic status (anticoagulant or no-anticoagulant). Universal alert values for microbiology were: Positive blood culture: Positive cerebral spinal fluid (CSF) culture: Positive CSF Gram stain. There was no universal agreement regarding critically high (potentially toxic) therapeutic drugs, with two medical centers declining to notify physicians of any abnormally high therapeutic drug level. No other qualitative critical limits for other laboratory sections, such as physician notification of an unexpected malignancy (surgical pathology) were universal. Medical center specific critical limits, designed to meet the clinical needs of each facility, are the norm in the nine medical centers. Laboratories do need periodically to review their critical limit lists with appropriate clinical input to avoid including critical limits for laboratory tests not required for urgent physician notification and patient evaluation and treatment.