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There is a clinical need for pragmatic approaches to measure integrated hemostatic reactions in whole blood rapidly, using small volumes of blood. The authors have applied T2 magnetic resonance (T2MR) to assess coagulation reactions based on partitioning of red blood cells and proteins that occurs during fibrin formation and platelet-mediated clot contraction. T2MR is amenable to measuring clotting times, individual coagulation factors, and platelet function. T2MR also revealed a novel “hypercoagulable” signature characterized by fibrin clots almost insusceptible to fibrinolysis that surround tessellated arrays of polyhedral erythrocytes (“third peak”). This signature, which develops under conditions associated with intense clot formation in vitro, may help identify patients at risk of developing thrombosis and for monitoring antithrombotic therapies in the future.

Molecular-based carbapenem resistance testing in Gram-negative bacterial bloodstream infections (BSIs) is currently limited because of the reliance on positive blood culture (BC) samples. The T2Resistance™ panel may now allow the detection of carbapenemase- and other β-lactamase encoding genes directly from blood samples. We detected carbapenem resistance genes in 11 (84.6%) of 13 samples from patients with BC-documented BSIs (10 caused by KPC-producing Klebsiellapneumoniae and 1 caused by VIM/CMY-producing Citrobacter freundii). Two samples that tested negative for carbapenem resistance genes were from patients with BC-documented BSIs caused by KPC-producing K. pneumoniae who were receiving effective antibiotic therapy. In conclusion, our findings suggest that the T2Resistance™ panel can be a reliable tool for diagnosing carbapenem-resistant Gram-negative bacterial BSIs.

In early Lyme disease (LD), serologic testing is insensitive and seroreactivity may reflect active or past infection. In this study, we evaluated a novel assay for the direct detection of three species of Borrelia spirochetes in whole blood. The T2 magnetic resonance (T2MR) assay platform was used to amplify Borrelia DNA released from intact spirochetes and to detect amplicon. Analytical sensitivity was determined from blood spiked with known concentrations of spirochetes, and the assay's limit of detection was found to be in the single-cell-per-milliliter range: 5 cells/ml for B. afzelii and 8 cells/ml for Borrelia burgdorferi and Borrelia garinii . Clinical samples ( n = 66) from confirmed or suspected early LD patients were also analyzed. B. burgdorferi was detected using T2MR in 2/2 (100%) of blood samples from patients with confirmed early LD, based on the presence of erythema migrans and documentation of seroconversion or a positive real-time blood PCR. T2MR detected B. burgdorferi in blood samples from 17/54 (31%) of patients with probable LD, based on the presence of erythema migrans without documented seroconversion or of documented seroconversion in patients with a compatible clinical syndrome but without erythema migrans. Out of 21 clinical samples tested by real-time PCR, only 1 was positive and 13 were negative with agreement with T2MR. An additional 7 samples that were negative by real-time PCR were positive with T2MR. Therefore, T2MR enables a low limit of detection (LoD) for Borrelia spp. in whole blood samples and is able to detect B. burgdorferi in clinical samples.

Background ESKAPE bacteria are thought to be especially resistant to antibiotics, and their resistance and prevalence in bloodstream infections are rising. Large studies are needed to better characterize the clinical impact of these bacteria and to develop algorithms that alert clinicians when patients are at high risk of an ESKAPE infection. Methods From a US data set of >1.1 M patient encounters, we evaluated if ESKAPE pathogens produced worse outcomes than non-ESKAPE pathogens and if an ESKAPE infection could be predicted using simple word group algorithms built from decision trees. Results We found that ESKAPE pathogens represented 42.2% of species isolated from bloodstream infections and, compared with non-ESKAPE pathogens, were associated with a 3.3-day increase in length of stay, a $5500 increase in cost of care, and a 2.1% absolute increase in mortality (P < 1e-99). ESKAPE pathogens were not universally more resistant to antibiotics, but only to select antibiotics (P < 5e-6), particularly against common empiric therapies. In addition, simple word group algorithms predicted ESKAPE pathogens with a positive predictive value of 7.9% to 56.2%, exceeding 4.8% by random guessing (P < 1e-99). Conclusions Taken together, these data highlight the pathogenicity of ESKAPE bacteria, potential mechanisms of their pathogenicity, and the potential to predict ESKAPE infections upon admission. Implementing word group algorithms could enable earlier and targeted therapies against ESKAPE bacteria and thus reduce their burden on the health care system.

Purpose Infants undergoing a cardiac operation are at high risk for postsurgical bleeding. To date, there are no highly predictive models for postsurgical bleeding in this population. This study's objective was to assess the predictive ability of T2 magnetic resonance (T2MR). Description T2MR uses magnetic resonance to detect clot formation characteristics on a small blood sample and provides hemostatic indicators that can assess bleeding risk. Evaluation This prospective, single-institution study enrolled 100 patients younger than 12 months old undergoing a cardiac operation from April 27, 2015, to September 21, 2016. The primary end point was postsurgical bleeding within 24 hours after the procedure. T2MR data were modeled with a binary recursive partitioning algorithm with randomized cross-validation. The tight clot metric produced the highest univariate discrimination of bleeding (receiver operator characteristic curve, 0.64; classification accuracy, 72%), and along with the platelet function metric, demonstrated highest relative importance based on Gini index splitting (Salford Systems, San Diego, CA). Multivariate modeling with cross-validation showed mean receiver operator characteristic curve area of 0.74 and classification accuracy of 82%. Conclusions T2MR tight clot and platelet function metrics were associated with bleeding events.

Objectives: The clinical diagnosis of qualitative platelet disorders (QPDs) based on light transmission aggregometry (LTA) requires significant blood volume, time, and expertise, all of which can be barriers to utilization in some populations and settings. Our objective was to develop a more rapid assay of platelet function by measuring platelet-mediated clot contraction in small volumes (35 µL) of whole blood using T2 magnetic resonance (T2MR). Methods: We established normal ranges for platelet-mediated clot contraction using T2MR, used these ranges to study patients with known platelet dysfunction, and then evaluated agreement between T2MR and LTA with arachidonic acid, adenosine diphosphate, epinephrine, and thrombin receptor activator peptide. Results: Blood from 21 healthy donors was studied. T2MR showed 100% agreement with LTA with each of the four agonists and their cognate inhibitors tested. T2MR successfully detected abnormalities in each of seven patients with known QPDs, with the exception of one patient with a novel mutation leading to Hermansky-Pudlak syndrome. T2MR appeared to detect platelet function at similar or lower platelet counts than LTA. Conclusions: T2MR may provide a clinically useful approach to diagnose QPDs using small volumes of whole blood, while also providing new insight into platelet biology not evident using plasma-based platelet aggregation tests.

NMR relaxometry is a powerful technique used to study and measure the relaxation rates of nuclear spins in complex environments. The relaxation rates depend strongly on the mobility of the microscopic environment and the strength of the applied magnetic field. T2 Biosystems has developed the T2 Magnetic Resonance (T2MR) platform, which enables the detection and measurement of a variety of diagnostic targets, including molecular targets (DNA, RNA), immunodiagnostics (proteins, small molecules) and a broad range of functional hemostasis measurements. This methodology enables a first-in-class, fully-automated test for fungal sepsis and has a limit of detection as low as 1 CFU/mL, compared to the 100 to 1,000 CFU/mL achieved by PCR-based in vitro diagnostics. Results indicate this sensitive and rapid test may significantly reduce the high mortality and the high cost of care for Candida infections. T2MR technology is also being used investigationally to evaluate hemostasis disorders, which require diagnostic identification and monitoring for both acute and chronic conditions that range from traumatic injury to routine monitoring of anticoagulant therapy, evaluation of clotting diseases and evaluation of bleeding disorders.T2MR measurements enable a comprehensive assessment of a patient's hemostasis status by determining multiple parameters including clotting times, platelet function, fibrinogen, and fibrinolysis from a single sample with data analysis beginning in as short as 5 minutes at the point of care using just 40 microliters of blood. By providing a rapid and accurate global assessment of a patient's hemostasis state, T2MR has the potential to significantly assist with the active management of hemostasis disorders while reducing both healthcare costs and mortality.

T2 magnetic resonance (T2MR®) is a powerful technique for the detection of minute concentrations of nucleic acids in complex matrices. Magnetic nanoparticles (MPs) with conjugated capture probes change states from dispersed to clustered in the presence of their target nucleic acids, a process that results in a dramatic change in T2MR signal. Unlike optical detection methods, T2MR is agnostic to solution opacity, and detection can be performed in many biological solutions, including blood, urine, and dialysate, without the need for lengthy nucleic acid extraction and purification techniques. High sensitivity is achieved by using large sample volumes for low concentration targets and minimal processing to reduce target loss. Specificity is driven by amplification primer and capture probe design combined with a highly discriminatory detection system. This method has been applied to the rapid detection of Candida spp. causing fungal sepsis, and limits of detection (LoDs) as low as 1 colony-forming units (CFU)/mL have been achieved directly from the blood. Similarly low LoDs have been demonstrated for species causing bacterial sepsis and Lyme disease. Clinical studies utilizing the automated T2Candida Panel® indicated an overall 91.1% sensitivity and 99.4% specificity per assay as compared to blood culture. Results were obtained in 3–5 h directly from patient blood, as opposed to the 2–5 days for results from blood culture. The T2MR method was also shown to detect invasive candidiasis, an infection that often cannot be diagnosed by blood culture.

Background Antibiotic-resistant bacteria are spread through selective pressure from the use of broad-spectrum empirical therapies, mobile genetic elements that pass resistance genes between species, and the inability to rapidly and appropriately respond to their presence. Resistance gene identification is often performed with post culture molecular diagnostic tests. The T2Resistance Panel, which detects methicillin resistance genes mecA/C; vancomycin resistance genes vanA/B; carbapenemases blaKPC, blaOXA-48,blaNDM, blaVIM, and blaIMP; AmpC β-lactamases blaCMY and blaDHA; and extended-spectrum β-lactamases blaCTX-M directly from patient blood samples, is based on T2 magnetic resonance (T2MR), an FDA-cleared technology with demonstrated high sensitivity and specificity for culture-independent bacterial and fungal species identification. Here we report the clinical performance of T2MR detection of resistance genes directly from patient blood samples. Methods Patients with a clinical diagnosis of sepsis and an order for blood culture (BC) were enrolled in the study at two sites. BCs were managed using standard procedures and MALDI-TOF for species identification. Resistance testing with the T2MR assay was performed on a direct patient draw and compared with diagnostic test results from concurrent BC specimen and BC specimen taken at other points in time. The potential impact on therapy was evaluated through patient chart review. Results T2MR detected the same resistance genes as detected by post culture diagnostics in 100% of samples from concurrent blood draws. Discordant results occurred when T2MR was taken ≥48 hours after BC for patients on antimicrobial therapy. The average time to positive result was 5.9 hours with T2MR vs. 30.6 hours with post-culture molecular testing. Conclusion The T2Resistance Panel detected antibiotic resistance genes in clinical samples and displayed agreement with post culture genetic testing. T2MR results were achieved faster than culture-dependent diagnostic testing results and may allow for an earlier change from empiric to directed therapy. The use of culture-independent diagnostics like T2MR could enable a quicker response to antibiotic-resistant organisms for individual patients and developing outbreaks. Disclosures All authors: No reported disclosures.

Background Candida auris is now recognized worldwide as a virulent pathogen that is difficult to manage, resulting in high mortality rates. The majority of C.auris isolates have exhibited resistance to one or more antifungal agents. Nosocomial infections caused by C.auris are growing due to the increasing rate of colonization and environmental causes. The diagnostic tests available for the identification of C. auris are limited to date. Additionally, microbiological cultures and subsequent identification of Candida species require 2–5 days, and have a sensitivity of approximately 50%. Accurate diagnosis of a C. auris infection is also hampered by misidentification of C. auris as other species, commonly C. haemulonii and Saccharomyces cerevisiae. Here we evaluate the use of the T2MR platform for the highly sensitive, rapid species level identification of C. auris, C. lusitaniae and C. haemulonii in whole blood samples. Methods A multiplex assay targeting C. auris, C. lusitaniae, and C. haemulonii was developed using cultured cells spiked in K2EDTA anticoagulated blood from healthy human donors. C. auris isolates received from the CDC were cultured overnight, automated cell counting was used to determine concentration. From this stock, the culture was diluted to a target titer, and inoculated into whole blood, followed by confirmation plating to confirm cell titer. Four mL spiked blood samples were processed on the T2Dx Instrument. Results Sensitive and specific detection of C. auris was achieved direct from blood in less than 4 hours on the T2Dx Instrument. A Limit of Detection (LoD) for C. auris was demonstrated to be ≤10 CFU/mL. T2MR signals of samples spiked with target were approximately 30 times higher than samples with no target present, and no cross reactivity was observed between C.auris, C. haemulonii, C. lusitaniae and C. krusei. Conclusion Low concentrations of Candida cells can be detected and identified by T2MR. This prototype assay potentially allows for the rapid screening and identification of patients infected with Candida auris with high specificity and sensitivity, aiding in the hospital management and targeted therapy of this emerging multi-drug resistant pathogen. Disclosures B. Manning, T2 Biosystems: Employee and Shareholder, Salary; J. L. Snyder, T2 Biosystems: Employee and Shareholder, Salary; B. Chang, T2 Biosystems: Employee and Shareholder, Salary; C. Wong, T2 Biosystems: Employee and Shareholder, Salary; T. Higa, T2 Biosystems: Employee and Shareholder, Salary; R. Shivers, T2 Biosystems: Employee and Shareholder, Salary; T. J. Lowery, T2 Biosystems: Employee and Shareholder, Salary

BACKGROUND Existing approaches for measuring hemostasis parameters require multiple platforms, can take hours to provide results, and generally require 1–25 mL of sample. We developed a diagnostic platform that allows comprehensive assessment of hemostatic parameters on a single instrument and provides results within 15 min using 0.04 mL of blood with minimal sample handling. METHODS T2 magnetic resonance (T2MR) was used to directly measure integrated reactions in whole blood samples by resolving multiple water relaxation times from distinct sample microenvironments. Clotting, clot contraction, and fibrinolysis stimulated by thrombin or tissue plasminogen activator, respectively, were measured. T2MR signals of clotting samples were compared with images produced by scanning electron microscopy and with standard reference methods for the following parameters: hematocrit, prothrombin time, clot strength, and platelet activity. RESULTS Application of T2MR methodology revealed conditions under which a unique T2MR signature appeared that corresponded with the formation of polyhedral erythrocytes, the dynamics and morphology of which are dependent on thrombin, fibrinogen, hematocrit, and platelet levels. We also showed that the T2MR platform can be used for precise and accurate measurements of hematocrit (%CV, 4.8%, R2 = 0.95), clotting time (%CV, 3.5%, R2 = 0.94), clot strength (R2 = 0.95), and platelet function (93% agreement with light transmission aggregometry). CONCLUSIONS This proof-of-concept study demonstrates that T2MR has the potential to provide rapid and sensitive identification of patients at risk for thrombosis or bleeding and to identify new biomarkers and therapeutic targets with a single, simple-to-employ analytic approach that may be suitable for routine use in both research and diverse clinical settings.

Contraction of blood clots is necessary for hemostasis and wound healing and to restore flow past obstructive thrombi, but little is known about the structure of contracted clots or the role of erythrocytes in contraction. We found that contracted blood clots develop a remarkable structure, with a meshwork of fibrin and platelet aggregates on the exterior of the clot and a close-packed, tessellated array of compressed polyhedral erythrocytes within. The same results were obtained after initiation of clotting with various activators and also with clots from reconstituted human blood and mouse blood. Such close-packed arrays of polyhedral erythrocytes, or polyhedrocytes, were also observed in human arterial thrombi taken from patients. The mechanical nature of this shape change was confirmed by polyhedrocyte formation from the forces of centrifugation of blood without clotting. Platelets (with their cytoskeletal motility proteins) and fibrin(ogen) (as the substrate bridging platelets for contraction) are required to generate the forces necessary to segregate platelets/fibrin from erythrocytes and to compress erythrocytes into a tightly packed array. These results demonstrate how contracted clots form an impermeable barrier important for hemostasis and wound healing and help explain how fibrinolysis is greatly retarded as clots contract.

Candida spp. cause both local and disseminated infections in immunocompromised patients. Bloodstream infections of Candida spp., known as "candidemia," are associated with a high mortality rate (40%), which is mainly attributed to the long diagnostic time required by blood culture. We introduce a diagnostic platform based on T2 magnetic resonance (T2MR), which is capable of sensitive and rapid detection of fungal targets in whole blood. In our approach, blood-compatible polymerase chain reaction is followed by hybridization of the amplified pathogen DNA to capture probe-decorated nanoparticles. Hybridization yields nanoparticle microclusters that cause large changes in the sample's T2MR signal. With this T2MR-based method, Candida spp. can be detected directly in whole blood, thus eliminating the need for analyte purification. Using a small, portable T2MR detection device, we were able to rapidly, accurately, and reproducibly detect five Candida species within human whole blood with a limit of detection of 1 colony-forming unit/ml and a time to result of

Patients with severe factor VIII (FVIII) deficiency (hemophilia A [HemA]) develop neutralizing antibodies (inhibitors) against FVIII in up to ~30% of cases. For HemA patients with inhibitors, activated recombinant factor VII (rFVIIa) is a treatment option. High levels of rFVIIa are required for treating HemA patients with inhibitors to induce direct activation of factor X on the surface of activated platelets via a tissue factor (TF)-independent mechanism (Hoffman M, Monroe DM. Thromb Res. 2010;125(suppl 1):S16-S18). To assess how rFVIIa-mediated clot formation in HemA patients with inhibitors may differ from unaffected individuals, we compared the effect of rFVIIa on HemA versus control (or HemA supplemented with 100% FVIII) clot formation in human and/or mouse systems. By TF-induced thrombin generation assay, increasing rFVIIa from 5 nM to 100 nM did not appreciably alter the kinetics or extent of thrombin generation compared with the same human HemA plasma containing 100% FVIII. Confocal microscopy of human HemA plasma clots generated with 75 nM rFVIIa and TF showed few branching fibrin fibers and an open fibrin meshwork. In contrast, TF-induced coagulation of the same HemA plasma containing 100% FVIII formed fibrin clots with numerous branches, interconnecting to form a dense meshwork. To confirm that these findings reflect rFVIIa-mediated clot formation in vivo, we assessed the intrinsic coagulation of mouse HemA whole blood collected without anticoagulant and spiked with rFVIIa. Intrinsic coagulation with rFVIIa was assessed by T2 magnetic resonance (T2MR), a technique capable of monitoring the separation of whole blood into serum, loose-clot, and tight-clot compartments during coagulation (Skewis et al. Clin Chem. 2014;60:1174-1182; Cines et al. Blood. 2014;123:1596-1603). By T2MR, rFVIIa induced the separation of HemA whole blood into the serum and clot compartments, indicating that the reduced fibrin generation with rFVIIa did not interfere with whole blood coagulation. Furthermore, saphenous vein puncture of HemA mice treated with rFVIIa showed a dose-dependent decrease in clot times. Scanning electron microscopy of the clots extracted from these HemA mice indicated markedly different composition than clots extracted from wild-type mice. In wild-type clots, fibrin and polyhedral erythrocytes formed a large proportion of the total structures. In contrast, clots from rFVIIa-treated HemA mice consisted primarily of platelets and erythrocytes with forms intermediate between discoid and polyhedral but, surprisingly, low fibrin content. Taken together, these data suggest that rFVIIa-mediated clot formation may require greater activated platelet involvement, which would be consistent with the TF-independent mechanism of action proposed for rFVIIa in HemA. Finally, the compositional difference between clots from wild-type versus HemA mice dosed with rFVIIa suggest that evaluating HemA therapies for their ability to form more physiologic clots could be an approach to improve treatment options for patients with HemA. Disclosures Leong: Bayer: Employment. Xu:Bayer: Employment. Mallari:Bayer: Employment. Wong:Bayer: Employment. Sim:Bayer: Employment. Cuker:Stago: Consultancy; Genzyme: Consultancy; Amgen: Consultancy; Biogen-Idec: Consultancy, Research Funding; T2 Biosystems: Research Funding. Marturano:T2 Biosystems: Employment. Lowery:T2 Biosystems: Employment. Kauser:Bayer: Employment. Weisel:Bayer: Research Funding.

To keep the water supply safe and to ensure a swift and accurate response to a water supply contamination event, rapid and robust methods for microbial testing are necessary. Current technologies are complex, lengthy and costly and there is a need for rapid, reliable, and precise approaches that can readily address this fundamental security and safety issue. T2 Biosystems is focused on providing solutions to this problem by making breakthroughs in nanotechnology and biosensor techniques that address the current technical restrictions facing rapid, molecular analysis in complex samples. In order to apply the T2 Biosystems nucleic acid detection procedure to the analysis of nucleic acid targets in unprocessed water samples, Bacillus thuringeinsis was selected as a model organism and local river water was selected as the sample matrix. The initial assay reagent formulation was conceived with a manual magnetic resonance reader, was optimized using a high throughput system, and transferred back to the MR reader for potential field use. The final assay employing the designed and manufactured instruments was capable of detecting 10 CFU/mL of B. thuringiensis directly within the environmental water sample within 90 minutes. Further, discrimination of two closely related species of Bacilli was accomplished using the methods of this project; greater than 3-fold discrimination between B. cereus and B. thuringiensis at a concentrations spanning 10 CFU/mL to 10{sup 5} CFU/mL was observed.

Background Contraction of blood clots is necessary for hemostasis, wound healing and to restore flow past obstructive thrombi. However, little has been known about the structure of contracted clots and mechanisms of contraction. Erythrocytes, biconcave cells that are highly deformable to allow their passage through the microvasculature, are abundant in venous thrombi, and to a lesser extent in arterial thrombi. Erythrocytes promote hemostasis, but their participation in clot contraction has not been reported. Here we study the mechanisms of clot contraction and the roles of erythrocytes, platelets and fibrin, and show that erythrocyte shape change into compressed polyhedrocytes allows tight packing consistent with the major function of clots to stem bleeding. Methods Whole blood was clotted by recalcification and addition of thrombin or kaolin, while following the process of clotting, including contraction, with a new technique using T2 magnetic resonance. We examined the structure and composition of contracted whole blood clots by scanning electron microscopy and confocal light microscopy. Results Contracted clots display a remarkable structure, with a close-packed, tessellated array (or mosaic tiling of space) of compressed polyhedral erythrocytes (called polyhedrocytes) on the interior and a meshwork of fibrin and platelet aggregates on the exterior. Little fibin and few platelets were found on the interior of the contracted clots. The same results were obtained with both thrombin and kaolin as activators of clotting and also with reconstituted human blood and clots prepared from mouse blood. Confocal microscopy of hydrated clots confirms the results of scanning electron microscopy. The mechanical nature of this shape change was confirmed by polyhedrocyte formation from the forces of centrifugation of blood without clotting. Platelets (with their cytoskeletal motility proteins) and fibrin(ogen) (as the substrate bridging platelets for contraction) are required to generate the forces necessary to segregate platelets/fibrin from erythrocytes and to compress erythrocytes into a closely packed polyhedral array. To assess the density of packing of the polyhedral erythrocytes, we replaced the water surrounding the clots with D2O and observed by T2 magnetic resonance that hydrogen/deuterium exchange for the contracted clots was very slow, consistent with their very tightly packed, almost impermeable structure. The same polyhedrocyte structures were observed from in vivo thrombi aspirated by cardiologists from the coronary arteries of ST-elevation myocardial infarction patients. Summary/Conclusions We have observed a previously undiscovered, naturally occurring erythrocyte function and morphology, closely packed polyhedra, in contracted clots and thrombi, and an unexpected spatial redistribution of platelets and fibrin that occurs during contraction. Clot contraction is an essential part of hemostasis, since both human genetic disorders of platelet myosin IIA and megakaryocyte myosin IIA-knock out mice show a bleeding phenotype. These observations on contracted clots imply that they are stiff, rigid structures that can form an impermeable, watertight seal. On the one hand, contraction of clots within the vasculature may relieve obstruction of blood vessels and allow recanalization, especially in the venous system. On the other hand, these results account for long-standing clinical observations that fibrinolysis is greatly prolonged following clot contraction, since perfusion or diffusion of lytic enzymes into these tightly packed polyhedral erythrocytes would be nearly impossible. These results suggest a vital role for erythrocytes and clot contraction in hemostasis and wound healing. Disclosures: No relevant conflicts of interest to declare.

Abstract 1118 There are no currently available tests to rapidly assess and reliably identify both impaired hemostasis and hypercoagulable states, in part because of difficulties in measuring integrated reactions in whole blood using a single sensitive and clinically useful platform. Methods like T2 magnetic resonance (T2MR) can provide rich information from complex samples, such as changes in the blood during hemostasis, by measuring signals emanating from the hydrogen nuclei within the sample, primarily in water. We used a 14”x6”x7” portable instrument to measure changes in T2MR that provide a continuous report on the dynamically changing microscopic environment of water during coagulation of whole blood (WB), platelet-poor or platelet-rich plasma (PRP). In these initial foundational studies, we measured T2MR continuously over 20 mins using 34 μL blood samples from consented normal adult donors. We tested clotting of WB initiated by the addition of thrombin or kaolin + calcium. Platelet activation was achieved in WB by addition of ADP or arachidonic acid in the presence of reptilase and factor XIIIa with and without addition of the platelet inhibitors aspirin or 2-methylthioadenosine 5'-monophosphate (2-MeSAMP) and results were confirmed by standard platelet aggregometry. At normal platelet counts from 1.5–3×105/μL and normal hematocrit (HCT) from 38%-48%, T2MR gave two curves corresponding to: (1) water trapped within a retracted clot and (2) water in the surrounding liquid, i.e. serum (Fig. 1a). Platelet counts Our proof-of-principle studies show that T2MR technology can be applied to measurement of blood clotting across a range of hemostatic conditions. This single technology may be applicable to the study, diagnosis, and management of a spectrum of disorders that range from impaired hemostasis to hypercoagulable states. These T2MR studies represent the first application of this technology to hemostasis and thrombosis. Additional studies will be needed to develop a more complete understanding of the biochemical events measured by T2MR and to more fully explore its clinical utility. Figure 1. Examples of T2MR 3D surfaces for 34 μL of citrated whole blood mixed activated by adding a dried formulation of CaCl2 (11 mM) and kaolin ( Disclosures: Cines: T2 Biosystems: Research Funding. Lebedeva:T2 Biosystems: Research Funding. Massefski:T2 Biosystems: Employment. Papkov:T2 Biosystems: Employment. Thayer:T2 Biosystems: Employment. Lowery:T2 Biosystems: Employment.

Advances in magnetic resonance (MR) miniaturization, along with nanoparticles and biotechnology, are extending MR applications in diagnostics to beyond the medical imaging regime. The principles behind magnetic resonance switch (MRSw) biosensors, as well as a summary of rapidly developing fields including MR miniaturization and MRSw demonstrations, are presented here. Due to the range of applications of MRSw biosensor tests and the breakthroughs in downsized instruments, continued development will enable the deployment of MRSw biosensors in a wide variety of settings and with potentially unlimited targets.