Summary. Background: To ensure proper clinical decision-making and avoid preventable harm, the quality of point-of-care (POC) device measures is routinely assessed. Traditional analyses may not reveal clinically important diagnostic errors. Objectives: To compare results between a novel analytic framework and traditional analyses. Methods: Patients in four anticoagulation clinics provided two measures of the International Normalized Ratio (INR) at the same visit as part of routine quality assurance: one via a venous sample and one fingerstick. These were assessed with Hemochron POC devices. Traditional, quarterly, quality assurance assessments emphasized correlation analysis. The novel analysis used enhanced graphics and a validated assessment of clinical decision-making. Results: 1518 paired INRs were analyzed. The correlation between the POC and laboratory assessments ranged between 0.84 and 0.91. Traditional quality assurance showed that the Hemochron devices were acceptable for continued use in each quarterly analysis. Enhanced graphical analysis demonstrated that the Hemochron devices never reported seven common INR values. The Hemochron devices systematically inflated values < 3 and deflated values > 4, biasing results towards the target INR range. Consequently, the Hemochron devices lead to a different clinical decision than the clinical laboratory measure in 31% of cases (458/1466; 95% confidence interval [CI] 29–34). When the reference INR was low, the Hemochron devices would not result in appropriate dose increases in 52% of cases (95% CI 48–56), placing these patients at risk for a significant adverse drug event. Conclusions: Our novel, clinically relevant analysis revealed previously undetected deficiencies in our POC INR devices, and our approach should be adopted by industry, regulators, and institutions.