Methods

1. Abstract Demographics Objective: D-dimer, a protein fragment remaining after the degradation of a blood clot, can be measured in the blood to determine the likelihood of a vascular traumatic event. Most commonly the test is used to rule out deep vein thrombosis and pulmonary embolisms. From a diagnostic standpoint these VTEs can share the same symptoms (shortness of breath, chest pain, and leg swelling) as a host of other medical problems so it is imperative to rule out a thrombosis as soon as possible. Point-of care devices shorten the turn around time for blood test results and therefore prove valuable in an emergent situation. Our study measured D-dimer levels on the AQT90 FLEX (Radiometer Medical ApS), a point-of-care device against the mini Vidas (bioMérieux, Inc), used in the clinical laboratory to determine the degree of correlation between the two assays. Methods: Data was collected from 116 unique individuals enrolled at UCSF. Of the subjects, 12 were diagnosed with PEs and one with a DVT. The plasma samples were collected on sodium citrate and were obtained frozen from the clinical labs after being used for clinical testing. The samples were defrosted and tested in batches on the AQT90 FLEX and mini Vidas within 2 hours of each other. Subjects who were not diagnosed at time of enrollment with a VTE were then contacted 30 days later to determine if any new thrombosis had occurred. Results: The subjects consisted of men (n=49) and women (n=67) with a mean age of 51.1 years (SD=17.1). Their ethnicities were covered in five groups; White(n=40), Black(n=31), Asian(n=12), Hispanic(n=8) and Other(n=16). Well’s scores captured for 51 subjects included Low(n=30), Moderate(n=19) and High(n=2), although none of the VTEs received a Well’s score. Of the 103 patients who did not have a VTE, 89 were contacted and none had thromboses at the 30 day follow up point. One patient expired due to unrelated causes and another suffered a PE several months later. The clinical comparison show that there was concordance between the two assays with all but four results in respect to positive and negative tests. The AQT correctly identified a PE as positive and two subjects as negative that the Vidas reported to the contrary. The AQT also reported one false positive that the Vidas did not. The remaining 11 VTEs were identified as positive on both assays. Discussion: Comparing D-dimer assays is challenging. First of all a comparison should be primarily a clinical comparison because the specificities for D-dimer assays can be in the range from 30-90 %. As the number of false-positives is equal to 100 % minus specificity, it can be seen that a relatively high number of false-positives seems to be accepted. The main reason for this is that a D-dimer test is used for ruling out VTE in low-risk patients and that patients with a positive test are examined with a confirmatory method (imaging). The challenges come from the fact that D-dimer is not a standardized method. There exists no reference method and there are no international standards available. Furthermore, the D-dimer molecules belong to a heterogeneous group of molecules. This means that it should be known which method was used to interpret a result, and you cannot directly compare two results obtained with different methods. Conclusion: There is a strong concordance between the AQT90 Flex results and the predicate Vidas assay. As D-dimer is used as a rule out test, done before confirmatory imaging, the AQT provides accurate results from a point-of-care location to help health care providers make time sensitive diagnoses. Gender: Men (n=49) and Women (n=67) Age: Mean Age= 51.1 (SD=17.1) Ethnicity: White (n=40), Black (n=31), Asian (n=12), Hispanic (n=8), Other (n=16) VTE Breakdown: Pulmonary Embolism = 12 Deep Vein Thrombosis = 1 Negative VTE =103 Wells Score: Low =30 Medium =12 High =2 *Wells scores were obtained from 51 of the 116 patients • The project was funded by Radiometer Medical ApS who wanted to evaluate their AQT90 Flex, a multiplatform point-of-care analyzer, against the FDA approved mini Vidas. • 116 unique patients enrolled at UCSF • Sodium citrate plasma was tested from patients in the ED suspected of having a VTE • Left over samples were obtained frozen after being tested in the clinical lab • Testing on the AQT90 FLEX and mini Vidas were done within 2 hours of each other Comparison of the AQT90 FLEX and Mini Vidas Assays in the D-dimer Analysis for the Determination of Vascular Traumatic EventsE.N. Shea, A.H. Wu,S. Tu, A. Wong UCSF, San Francisco, Ca Results • Regression Analysis of the AQT90 FLEX and mini Vidas • Results above 5000ng/mL removed as these values are outside of measurable range while any result above 500ng/ML is considered a positive test • Results were in concordance with all but four results between assays • AQT90 identified a PE as positive and two patients as negative that the mini Vidas failed to accurately report • AQT90 reported one false positive that the mini Vidas did not Methods Conclusion The AQT 90 FLEX provides comparable results to the predicate, mini Vidas. Having a point-of-care D-dimer assay would allow doctors to rule out time sensitive diagnosis more quickly. Place closed tube inside of device when prompted by screen Select parameters for the sample from the touch screen Reload machine with next sample and wait for results to print