Denis M. Dwyre

Cell-Phone-Based Platform for Biomedical Device Development and Education Applications

In this paper we report the development of two attachments to a commercial cell phone that transform the phones integrated lens and image sensor into a 350× microscope and visible-light spectrometer. The microscope is capable of transmission and polarized microscopy modes and is shown to have 1.5 micron resolution and a usable field-of-view of 150×150 with no image processing, and approximately 350×350 when post-processing is applied. The spectrometer has a 300 nm bandwidth with a limiting spectral resolution of close to 5 nm. We show applications of the devices to medically relevant problems. In the case of the microscope, we image both stained and unstained blood-smears showing the ability to acquire images of similar quality to commercial microscope platforms, thus allowing diagnosis of clinical pathologies. With the spectrometer we demonstrate acquisition of a white-light transmission spectrum through diffuse tissue as well as the acquisition of a fluorescence spectrum. We also envision the devices to have immediate relevance in the educational field.

Transfusion-associated graft-versus-host disease.

Transfusion‐associated graft‐versus‐host disease (TA‐GvHD) is a rare complication of transfusion of cellular blood components producing a graft‐versus‐host clinical picture with concomitant bone marrow aplasia. The disease is fulminant and rapidly fatal in the majority of patients. TA‐GvHD is caused by transfused blood‐derived, alloreactive T lymphocytes that attack host tissue, including bone marrow with resultant bone marrow failure. Human leucocyte antigen similarity between the transfused lymphocytes and the host, often in conjunction with host immunosuppression, allows tolerance of the grafted lymphocytes to survive the host immunological response. Any blood component containing viable T lymphocytes can cause TA‐GvHD, with fresher components more likely to have intact cells and, thus, able to cause disease. Treatment is generally not helpful, while prevention, usually via irradiation of blood components given to susceptible recipients, is the key to obviating TA‐GvHD. Newer methods, such as pathogen inactivation, may play an important role in the future.

Hepatitis B, hepatitis C and HIV transfusion-transmitted infections in the 21st century

In the past, transfusion‐transmitted virus (TTV) infections were not uncommon. In recent years with advanced technologies and improved donor screening, the risk of viral transfusion transmission has been markedly reduced. Hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV) have all shown marked reduction in transmission rates. However, the newer technologies, including nucleic acid technology (NAT) testing, have affected the residual rates differently for these virally transmitted diseases. Zero risk, which has been the goal, has yet to be achieved. False negatives still persist, and transmissions of these viruses still occur, although rarely. It is known that HBV serological testing misses some infected units; likewise, HBV NAT–negative units have also been known to transmit the virus. Similarly, HIV minipool NAT–negative units have transmitted HIV, as recently as 2007; likely, these transmissions would have been prevented with single‐unit NAT testing. Newer technologies, such as pathogen inactivation (PI), will (ideally) eliminate these falsely test negative components, regardless of the original testing method used for detecting the viruses.

The effect of Dabigatran on select specialty coagulation assays

Dabigatran etexilate is a new oral anticoagulant that functions as a direct thrombin inhibitor. An inhibitor of thrombin has the potential to interfere with essentially all clot-based coagulation assays and select chromogenic assays, whereas the drug would not be expected to interfere in antigen-based assays. The purpose of this study was to evaluate the effect of dabigatran on various specialized coagulation assays using normal plasma specimens with varying concentrations of dabigatran (the active form of dabigatran etexilate). We have demonstrated that samples containing therapeutic levels of dabigatran may lead to underestimation of intrinsic factor activities with abnormal activated partial thromboplastin time (aPTT) mixing study results and a false-positive factor VIII Bethesda titer; overestimation of protein C and protein S activity and activated protein C resistance ratio when determined using aPTT-based methods; and overestimation of results based on chromogenic anti-IIa assays but no effect on antigen assays and select chromogenic assays.

Transfusion-Related Acute Lung Injury (TRALI): Current Clinical and Pathophysiologic Considerations

Transfusion-related acute lung injury (TRALI) is a rare transfusion reaction presenting as respiratory distress during or after transfusion of blood products. TRALI varies in severity, and mortality is not uncommon. TRALI reactions have equal gender distributions and can occur in all age groups. All blood products, except albumin, have been implicated in TRALI reactions. TRALI presents as acute respiratory compromise occurring in temporal proximity to a transfusion of a blood product. Other causes of acute lung injury should be excluded in order to definitively diagnose TRALI. Clinically and pathologically, TRALI mimics acute respiratory distress syndrome (ARDS), with neutrophil-derived inflammatory chemokines and cytokines believed to be involved in the pathogenesis of both entities. Anti-HLA and anti-neutrophil antibodies have been implicated in some cases of TRALI. Treatment for TRALI is supportive; prevention is important. It is suspected that TRALI is both underdiagnosed and underreported. One of the difficulties in the evaluation of potential TRALI reactions is, until recently, the lack of diagnostic criteria. A group of transfusion medicine experts, the American–European Consensus Conference (AECC), recently met and developed diagnostic criteria of TRALI, as well as recommendations for management of donors to prevent future TRALI reactions. In light of the AECC consensus recommendations, we report an incident of TRALI in an oncology patient as an example of the potential severity of the lung disease and the clinical and laboratory evaluation of the patient. We also review the literature on this important complication of blood transfusion that internists may encounter.

Measuring Dabigatran Concentrations Using a Chromogenic Ecarin Clotting Time Assay

Background: Clinicians managing patients receiving the direct thrombin inhibitor dabigatran may benefit in being able to determine the amount of drug present in selected situations. This may include assessment of accumulation, concurrent drug interactions, or adequate removal from circulation. The ability to estimate the amount of dabigatran present using the chromogenic ecarin assay (ECA) requires further clarification. Objective: To describe the reliability of dabigatran measurements using a chromogenic ECA. Methods: This was an evaluation of the ECA method that incorporated assessment of imprecision, linearity, accuracy, carryover, and lower limits of detection or blank. Pooled normal plasma enriched with dabigatran at concentrations of 0, 25, 50, 75, 100, 125, 150, 200, 300, 400, and 500 ng/mL were sent blinded to 3 laboratories in the United States to compare our ECA results with those of laboratories reporting dilute thrombin time methods (HEMOCLOT thrombin inhibitor assay) for measuring dabigatran. Trough and peak levels from 35 patients were also compared with mass spectrophotometry for assessing ECA accuracy. Results: The within-run or day-to-day imprecision was less than 10%, with high linearity (R2 = 0.989) and high degree of accuracy (R2 = 0.985; slope = 0.908) for levels ranging between 18 and 470 ng/mL and no carryover at 0 ng/mL noted. The ECA approach appeared to be more reliable at lower dabigatran concentrations. Conclusions: The chromogenic ECA appears to be an effective approach to determine the amount of dabigatran present. Further insights are necessary to determine how it can be used to reduce thromboembolic or bleeding complications in patients receiving dabigatran

The pathogenicity of von Willebrand factor in thrombotic thrombocytopenic purpura: reconsideration of treatment with cryopoor plasma

New developments in the understanding of thrombotic thrombocytopenic purpura (TTP) provide opportunities for improved patient care. A widely held historical model of TTP microvascular thrombosis implicated circulating ultralarge von Willebrand factor (ULVWF) in causing spontaneous platelet (PLT) aggregation. From this pathogenic model, concerns about ULVWF in fresh‐frozen plasma (FFP) used to treat patients led to widespread use of cryopoor plasma (CPP) as an alternative. There is scant evidence, however, that circulating ULVWF contributes to microvascular thrombosis in TTP. New evidence suggests that the formation of PLT aggregates in TTP may be mediated by VWF in the process of being released from endothelium. Moreover, clinical studies do not demonstrate superior efficacy of CPP compared to FFP in the treatment of TTP. Because CPP may have reduced concentrations of factors important in the treatment of TTP, including ADAMTS13 metalloprotease, a reappraisal of the use of CPP in the treatment of TTP is warranted.

Disseminated histoplasmosis presenting as thrombotic microangiopathy

BACKGROUND:  Thrombotic microangiopathies (TMA) are systemic vasoocclusive disorders associated with significant morbidity and mortality. Rapid and reliable diagnosis of TMA is critical. The diagnosis is complicated by a lack of objective and sensitive laboratory testing as well as multiple concurrent diseases, including infectious processes.

Platelet function abnormalities in qualified whole‐blood donors: effects of medication and recent food intake

Background and Objectives  Platelet function abnormalities have been reported in blood donors who have not consumed aspirin. Our objective was to identify factors other than aspirin that may contribute to impaired platelet function in qualified volunteer blood donors.

Comparison of six D-dimer methods in patients suspected of deep vein thrombosis

We evaluated six D-dimer methods to determine their sensitivity, specificity, and negative predictive values (NPV) in symptomatic patients suspected of deep vein thrombosis (DVT). In patients suspected of DVT a whole blood D-dimer test (SimpliRED, Agen) was performed, and then tested using enzyme-linked immunosorbent assay (VIDAS D-Dimer, BioMerieux; Asserachrome D-Di, Stago International; Dimertest Gold, Agen) and automated immunoturbidometric methods (Advanced D-Dimer, Dade Behring; MiniQuant, Biopool). Each D-dimer method was independently compared with radiographic results to determine sensitivity and NPV. There were 151 patients enrolled in the study. Thirty-five (23.2%) patients had a positive Doppler ultrasound, with 26 proximal, eight distal, and one patient with both proximal and distal thrombus. Two patients (1.3%) had inconclusive studies and were excluded from the analyses. For all patients, the sensitivities for the rapid D-dimer methods were: SimpliRED, 82.3% [95% confidence interval (CI), 80.3–84.3%]; VIDAS D-Dimer, 91.4% (95% CI, 89.9–92.9%); MiniQuant D-Dimer, 96.3% (95% CI, 95.1–97.5%); and Advanced D-Dimer, 97.1% (95% CI, 96.3–97.9%). The sensitivity improved for SimpliRED (86.4%; 95% CI, 83.3–89.4%), VIDAS D-Dimer (95.5%; 95% CI, 85.0–100%), MiniQuant D-Dimer (100%; 95% CI, 96.9–100%) and Advanced D-Dimer (100%; 95% CI, 98.9–100%) in the inpatient population. The automated immunoturbidometric methods, the MiniQuant D-Dimer and Advanced D-Dimer, demonstrated comparable sensitivities and NPV with the VIDAS D-Dimer method in symptomatic patients suspected of DVT, which would suggest that these newer D-dimer methods could be used as part of the diagnostic algorithm for patients suspected of DVT.