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

Background/Objectives: Critical limits define quantitative thresholds for life-threatening diagnostic test results that require immediate clinician notification and may prompt urgent intervention to prevent adverse outcomes. This study aims to (1) characterize point-of-care (POC) critical limits for adults and newborns using a comprehensive U.S. national database, (2) identify POC instruments associated with these limits, and (3) support harmonization of point-of-care testing (POCT) practices. 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 POC and central laboratory critical limits (at hospitals with POC), adult international normalized ratio (INR) data, and instrument usage. Results: Low and high glucose critical limits were the most frequently listed POC thresholds, with median values of 50 and 450 mg/dL, respectively, 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). A few hospitals assigned instrument-specific critical limits for the same analyte, and 55 hospitals did not specify instrument usage for any measurand. 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. Establishing standards, annual updating, and enforcing risk mitigation could enhance adoption and reliability. 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.