Critical Decision Thresholds for Urgent Physician Notification of Point-of-Care Testing Results

Background/Objectives: Critical limits represent quantitative thresholds of life-threatening diagnostic test results that require immediate clinician notification and may necessitate life-saving intervention to prevent adverse outcomes. Our goals are to report point-of-care critical limits for adults and newborns from a comprehensive U.S. national database, to identify POC instruments associated with the critical limits, and to support the harmonization of POCT practice. Methods: We gathered critical limit notification lists from 417 hospitals across all 50 states and Washington D.C., comprising university hospitals, trauma and heart centers, centers of excellence, community hospitals, and network hospitals. We extracted point-of-care critical limits, central laboratory critical limits (at hospitals with POC), adult international normalized ratio (INR) data, and instrument usage. Results: Low and high glucose critical limits (median values of 50 and 450 mg/dL, respectively) were the most frequently listed, reported by 73 hospitals (17.5%). Troponin was listed by ten hospitals, specified as troponin (n = 4), troponin I (n = 5), or “troponin TnI” (n = 1). Rarely, we encountered notification lists that assigned different critical limits to different instruments measuring the same analyte. Fifty-five hospitals did not specify instrument usage for any measurand on their notification list. The median differences in matched pairs of laboratory versus POC critical limits differed significantly (Wilcoxon signed-rank, P< 0.05) for low and high ionized calcium (N=21), low hemoglobin (N=23) and high INR critical limits for adults (N=27) and newborns (N=10). In some cases, matched pair analytes demonstrated identical critical limits. Conclusions: Harmonizing critical limit notification thresholds across point-of-care testing and different devices may improve consistency in clinical decision-making and patient outcomes. Despite the potential of POCT to shorten time to urgent intervention, relatively few hospitals currently include POCT critical limits on notification lists. Broader inclusion and transparent sharing of POCT critical values could harmonize practices across institutions, facilitate inter-institutional collaboration, and promote more timely and reliable responses to life-threatening diagnostic results.