Background: A D-dimer threshold <500ug/L has high negative predictive value (NPV) for venous thromboembolism (VTE), but is non-specific. Two strategies increase the specificity and utility (defined as the proportion of patients with a negative test) of D-dimer testing: 1) using a higher D-dimer threshold with increasing age (IAIT Strategy); and 2) using a high threshold in low clinical pretest probability (CPTP) patients and the standard threshold in moderate CPTP patients (CPTP Strategy). It is unknown whether the gain in specificity of the IAIT Strategy is simply due to using a higher threshold in some patients and whether the CPTP Strategy has better diagnostic accuracy than the IAIT Strategy. Methods: In a retrospective analysis of 1649 outpatients with suspected VTE, I compared the diagnostic accuracy of the IAIT Strategy to 1) its opposite: using a higher D-dimer threshold with decreasing age (DAIT strategy); 2) using a higher D-dimer threshold in all patients (Median Age Strategy); and 3) the CPTP Strategy. Results: The NPV of both the IAIT and DAIT Strategies was 99.6% and the NPV of the Median Age Strategy was 99.7%. The utility was almost identical in the IAIT and DAIT Strategies (50.9% vs. 50.6%) and greater in the Median Age Strategy (53.9%, p<0.001). The NPV of the CPTP and IAIT Strategies were 99.6% and 99.7%, respectively. The utility was higher in the CPTP Strategy than the IAIT Strategy (56.1% vs. 50.9%, p<0.001). Conclusions: The NPV and utility of using a higher D-dimer threshold in older patients (IAIT Strategy) is the same as using a higher D-dimer threshold in younger patients. The CPTP Strategy had the greatest utility while maintaining a high NPV and therefore appeared to be the optimal strategy of D-dimer interpretation. / Thesis / Master of Health Sciences (MSc)

This thesis describes the design and synthesis of small molecule derivatives and their polypeptide conjugates as high affinity binders for proteins: the D-dimer protein (D-dimer), a biomarker for diagnosis of thromboembolic diseases; human myeloperoxidase (MPO), a biomarker for cardiovascular diseases; and chitinases, potential targets for asthma therapy. The interactions between the synthetic binder molecules and those proteins were evaluated by surface plasmon resonance (SPR) biosensor analysis and fluorescence spectroscopy. Competition SPR experiments or other methods proved that the small molecule components of the binder molecules were critical for binding and specifically bound to the original binding site of small molecules. The binder molecules consisted of a 42-residue helix-loop-helix polypeptide conjugated to a small molecule via aliphatic spacers of suitable length. The small molecules could be any type of moderately binding structure. In the binder development for the D-dimer, the tetrapeptide GPRP with a dissociation constant Kd of 25 μM was used and the affinity of 4C15L8GPRP obtained was estimated to be approximately 3 nM. In the binder development for MPO, salicylhydroxamic acid (SHA) with Kd of 2 μM was used and the affinity of 4C37L34C11SHA obtained was estimated to be approximately 0.4 nM. In the binder development for chitinases, a theobromine derivative (pentoxifylline) with a Kd of 43±10 μM was used and the affinity of 4C37L34-P obtained was estimated to be considerably higher than that of pentoxifylline. The binder molecules were identified from a 16-membered pool of candidates obtained by conjugating the small molecules to each member of a set of 16 designed polypeptides. The affinities were greatly enhanced by 2-3 orders of magnitude, compared to the small molecule. The polypeptides did not bind to the proteins with measurable affinities. The discovery of these new synthetic binders for protein targets can pave the way to diagnostic tests in vivo or in vitro, independent of antibodies.

No description available.

The fibrinogen degradation product D-dimer is released in plasma during fibrinolysis. D-dimer analysis is mainly ordered for the exclusion of venous thromboembolism (VTE) in combination with a pre-test probability (PTP) score. D-dimer below 0,5 mg/L fibrinogen equivalent units (FEU) and a low PTP rules out VTE. D-dimer analysis contributes to the reduction of invasive and expensive imaging analyses, such as ultrasound and computed tomography. The Blekinge region primary care used a qualitative D-dimer point of care test (POCT) whose performance the clinical chemistry of Blekinge hospital had no insight into. The aim of the study was to investigate whether the qualitative D-dimer POCT was an adequate complement to the quantitative method used in the hospital laboratory. Fifty patients, whose blood samples arrived the laboratory in tubes with sodium citrate- and ethylenediaminetetraacetic acid (EDTA) additives, were chosen for the study. Citrate plasma was analyzed with the D-dimer laboratory method. Plasma and whole blood were analyzed with the D-dimer POCT. Quantitative results were converted to qualitative based on the cutoff value 0,5 mg/L FEU. POCT performance was computed and compared with the manufacturer’s specified values. A potential difference between the methods was evaluated with a Chi-squared test. A survey was performed where open care units answered questions regarding D-dimer POCT. The POCT performance was slightly lower than the manufacturer’s specifications. No statistically significant difference was seen between the methods. However, there were several sources of error with the latter. Some open care units mentioned weak lines in the reading area due to blood interference. / Vid fibrinolys av blodkoagel frisätts fibrinnedbrytningsprodukten D-dimer. D-dimeranalyser utförs främst för uteslutning av venös tromboembolism (VTE) i kombination med ett poängsystem för preanalytisk sannolikhet (PTP) för VTE. D-dimerhalter under 0,5 mg/L fibrinogenekvivalenta enheter (FEU) och en låg PTP utesluter med stor säkerhet VTE. Använd på rätt sätt bidrar D-dimeranalysen till att minimera onödiga invasiva och dyra undersökningar som ultraljud och datortomografi. I region Blekinge används en kvalitativ, patientnära analysmetod (PNA) för D-dimer vars prestanda Blekingesjukhusets laboratorium för klinisk kemi inte har någon insyn i. Studiens syfte var att undersöka om den kvalitativa PNA-metoden för D-dimer utgjorde ett lämpligt komplement till den kvantitativa metod som utfördes på klinisk kemi. Femtio patienter vars blodprov anlände laboratoriet i provrör med tillsats av natriumcitrat respektive etylendiamintetraättiksyra (EDTA) blev utvalda att delta i studien. D-dimer analyserades i citratplasma med laboratoriets analysmetod varefter plasma och tillhörande EDTA-blod analyserades med PNA-metoden. Kvantitativa resultat konverterades till kvalitativa efter beslutsvärdet 0,5 mg/L FEU. PNA-prestandan beräknades och jämfördes med tillverkarens angivna motsvarigheter. Med ett chi-squaretest undersöktes en eventuell signifikant skillnad mellan metodresultaten. En undersökning utfördes där regionens öppenvårdsenheter svarade på diverse frågor kring PNA-metoden. PNA-metodens beräknade prestanda var något lägre än tillverkarens. Ingen statistiskt signifikant skillnad förekom mellan laboratoriets metod och PNA-metoden, däremot fanns det flera potentiella felkällor hos den senare. Några öppenvårdsenheter vittnade om svåravlästa avläsningsområden på grund av blodinterferens.

Thrombosis and colorectal cancer have a bi-directional relationship. The presence of a colorectal malignancy results in an increased risk of developing a thrombosis and the presence of a thrombosis results in a worse cancer prognosis. The physiology causing this is at present unclear but it is proposed that proteins from the tissue factor (TF) pathway may be the instigator of this bi-directional relationship. The in-vitro studies have shown that in colorectal cancer TF impairs that action of colorectal cancer stem cells as demonstrated by reduced cancer sphere formation and also lower expression of the stem cell marker ALDH. The ability for a colorectal cell to avoid anoikis is impaired by a reduced TF level. Proliferation is affected by the level of expression of TF with a significant increase in proliferation with additional expression of TF. The increase in proliferation is further increased by the presence of TF’s ligand factor VIIa. Paradoxically reduced expression of TF also increases colorectal cancer expression. The ERK1/2 pathway offers a possible method by which TF and factor VIIa may exert their proliferative effects. In the prospective clinical cohort study (CHAMPion) abnormal expression of TF pathway proteins (TF, PAR1, PAR2 and thrombin) by both malignant epithelial and cancer associated stromal cells has been demonstrated. The stromal expression was independent of the epithelial expression and was only in stroma in close contact (0.1mm) with epithelial cells suggesting that the TF pathway proteins may have a role in stromal/epithelial communication. There was no link between the expression of TF pathway proteins and clinicopathological markers of a poor prognosis. The plasma expression of markers of TF pathway activation did not demonstrate any role as a biomarker for colorectal cancer or prognosis. The CHAMPion study has demonstrated that 7% of patients undergoing surgery for colorectal cancer have asymptomatic pre-operative DVTs present. A further 6% who were DVT free pre-operatively developed a DVT in the peri-operative period despite receiving venous thromboprophylaxis in line with current national guidelines. Pre-operative d-dimer may have the potential to identify those patients at risk of a post-operative VTE.This thesis establishes the role that TF has in promoting proliferation and anoikis resistance. It also confirms the abnormal expression of TF pathway proteins by colorectal cancer epithelial cells and for the first time demonstrates abnormal expression by the cancer associated stroma. The interaction between the stroma and epithelial cells, combined with the cellular effects of TF suggests that targeting this interaction may have a therapeutic role. The incidence of DVTs pre-operatively suggests that screening patients for the asymptomatic presence of a DVT may have an impact on their clinical outcome. The development of DVTs despite prophylaxis suggests that the level of anticoagulation is insufficient and current guidelines need to be revisited.

Inledning: Patienter med covid-19 har en ökad risk att drabbas av lungemboli. Symtomen som patienter med covid-19 har liknar många gånger symtom på lungemboli. Förhöjda D-dimer-värden ökar misstanken om lungemboli. Detta är dock svårt att tolka eftersom patienter med covid-19 kan ha förhöjda D-dimervärden på grund av infektionen. För att misstänka lungemboli behövs ett positivt utslag på D-dimer och beaktande av symtom och för att påvisa lungemboli behöver patienter genomgå en undersökning med datortomografi (DT). Syfte: Beskriva symtom och kliniska tecken hos patienter med covid-19 som genomgår en datortomografiundersökning med frågeställningen lungemboli. Genom syftet utformades frågeställningen: Ses någon skillnad i symtom och kliniska tecken hos patienter med covid-19 som får diagnosen lungemboli och de som inte får diagnosen lungemboli? Metod: Studien har genomförts som en allmän litteraturöversikt och innefattar elva vetenskapliga artiklar med kvantitativ metod. Resultat: Ingen signifikant skillnad kunde ses i symtom, fysiska mätvärden, ålder och kön hos patienter med covid-19 som diagnostiserades med lungemboli jämfört med de som inte diagnostiserades med lungemboli, men däremot sågs en signifikant skillnad i D-dimernivåerna. Alla patienter med covid-19 hade förhöjda D-dimernivåer, och de patienterna med lungemboli hade högre värden. Slutsats: Det gick inte att urskilja något D-dimergränsvärde som med säkerhet kan utesluta lungemboli hos patienter med covid-19. Symtom och fysiska mätvärden hos patienter med covid-19 som drabbats eller inte drabbats av lungemboli är lika varandra. Förhöjda D-dimer- nivåer hos patienter med covid-19 är vanligt. Detta gör att många patienter med covid-19 remitteras till DT med frågeställningen lungemboli. Röntgensjuksköterskan ska kunna avgöra om en undersökning är berättigad för att en patient inte ska bli utsatt av en onödig stråldos, vilket är komplicerat i detta fall.

Biological material is a common type of evidence found at a crime scene, and body fluid identification is an essential process in crime scene investigation. One of the most common types of body fluids found is blood. After a stain has been presumptively identified as blood through the use of a colorimetric chemical test, additional testing may be necessary to better characterize the stain. SERATEC PMB Test is a relatively new lateral flow immunochromatographic assay that targets human hemoglobin and D-dimer simultaneously in order to distinguish peripheral blood and menstrual blood at the same time. Elevated levels of D-dimer, a fibrin degradation product, are found in menstrual blood, thrombosis formation and as part of the postmortem process. A previous study investigated levels of D-dimer in menstrual, peripheral and postmortem blood using the SERATEC PMB Test. In this study, all postmortem blood samples showed positive results for both hemoglobin and D-dimer; all peripheral bloodstain samples from living individuals showed positive results for hemoglobin detection, and negative results for D-dimer detection; and most menstrual bloodstain samples showed positive D-dimer results. The results suggest that this assay could be considered a presumptive test for both postmortem blood and menstrual blood. However, as D-dimer concentrations vary between individuals, additional testing is necessary to conclusively distinguish postmortem blood, menstrual blood and peripheral blood from living individuals with especially high D-dimer levels.

Objective: Abnormal elevation of D-dimer levels is an important indicator of disseminated intravascular clotting. Therefore, we hypothesized that high D-dimer levels were associated with the risk of stroke and adverse clinical outcomes of patients with acute ischemic stroke (AIS) or transient ischemic attack (TIA). Methods: The present meta-analysis aimed to systematically analyze the associations between D-dimer and the risk of stroke as well as the clinical outcomes of patients with post-stroke or TIA. Meanwhile, dose–response analyses were conducted when there were sufficient data available. Three electronic databases including Pubmed, the Embase database, and the Cochrane Library were searched by two investigators independently. All the pooled results were expressed as risk ratios (RRs). Results: Finally, 22 prospective cohort studies were included into this meta-analysis. The results suggested that high D-dimer levels were associated with increased risks of total stroke (RR 1.4, 95%CI 1.20–1.63), hemorrhagic stroke (RR 1.25, 95%CI 0.69–2.25), and ischemic Stroke (RR 1.55, 95%CI 1.22–1.98), and the dose-dependent relationship was not found upon dose–response analyses. Besides, the high D-dimer levels on admission were correlated with increased risks of all-cause mortality [RR 1.77, 95% confidence interval (CI) 1.26–2.49], 5-day recurrence (RR 2.28, 95%CI 1.32–3.95), and poor functional outcomes (RR 2.01, 95%CI 1.71–2.36) in patients with AIS or TIA. Conclusions: On the whole, high D-dimer levels may be associated with the risks of total stroke and ischemic stroke, but not with hemorrhagic stroke. However, dose–response analyses do not reveal distinct evidence for a dose-dependent association of D-dimer levels with the risk of stroke. Besides, high D-dimer levels on admission may predict adverse clinical outcomes, including all-cause mortality, 5-day recurrence, and 90-day poor functional outcomes, of patients with AIS or TIA. More studies are warranted to quantify the effect of D-dimer levels on the risk of stroke or TIA, so as to verify and substantiate this conclusion in the future.

No description available.

No description available.