A case of Streptococcus canis bacteremia, osteomyelitis, sacroiliitis, myositis, and abscess.

BACKGROUND: Streptococcus canis is a group G beta-hemolytic Streptococcus species which normally resides on the skin and mucosal surfaces of dogs. Although it rarely causes infection in humans, our case and review of relevant literature demonstrate that this multi-host pathogen may be responsible for metastatic infection. We present an appropriate management strategy in such cases. CASE PRESENTATION: A previously healthy 26-year-old male presented to the emergency department with a 2-day history of erythema, pain, and swelling of the left ankle and foot, consistent with acute cellulitis. The patient was initially discharged home with a plan to complete a course of IV cefazolin as an outpatient, but later recalled after two sets of blood cultures grew gram positive cocci. Blood cultures speciated as Streptococcus canis. This was performed by identifying beta hemolytic strep on blood agar, then typed as Lancefield group G, followed by MALDI-TOF which distinguished S. canis. History was unremarkable except for a 2-week history of lower back pain precipitated by a wrestling injury. There was no canine bite or scratch wound, although the patient lives with a dog. CT spine was obtained which demonstrated right piriformis myositis and S1 osteomyelitis. MRI additionally demonstrated right erector spinae myositis, right sacroiliitis, and multiple collections in the right posterior paraspinal soft tissues. Transthoracic echocardiogram did not demonstrate valvular vegetations. The S. canis isolate was pan-susceptible and the patient was ultimately discharged home and completed a 8-week course of IV penicillin G. After completion of therapy, his symptoms, repeat imaging, and biochemical markers suggested resolution of infection on follow-up. CONCLUSIONS: We suggest that management of S. canis bacteremia should involve consideration of screening for metastatic infection and infectious diseases consultation. However, despite its potential for systemic involvement, S. canis is often susceptible to narrow spectrum antibiotics, and may be treated with penicillins.

Changes in factor XIII level during pregnancy.

Pregnancy is associated with significant haemostatic changes, with a progressive rise in most clotting factors. There is limited data on the changes of factor XIII (FXIII) level during pregnancy. This study assesses changes in FXIII activity during normal pregnancy and establish FXIII reference range during each trimester of pregnancy and immediate postnatal period. This is a cross sectional study of 376 women with normal uneventful pregnancies. Plasma FXIII activity was measured during first (weeks 0-12, n = 116), second (weeks 13-28, n = 132), third trimester (weeks 29-42, n = 128) and postnatal (day 0-3; n = 30). Samples were also collected from non-pregnant women (n = 25) as a control group. FXIII was assayed on CS-5100 analyser using chromogenic reagent. The mean ± SD FXIII activity was 112 ± 29 IU dL(-1) during first trimester, 96 ± 26 IU dL(-1) during second trimester, 83 ± 21 IU dL(-1) during third trimester, 90 ± 19 IU dL(-1) during postnatal period, and 113 ± 26 IU dL(-1) in the control. The reference range was calculated during the first (55-169 IU dL(-1)), second (45-147 IU dL(-1)), third trimester (42-125 IU dL(-1)) and postnatal period (61-137 IU dL(-1)). There was a significant reduction in the mean FXIII activity during the second and third trimester compared to the first trimester and control group (P < 0.0001). During the immediate postnatal period, the mean FXIII activity was not statistically different compared to the third and second trimester levels but was significantly lower compared to the first trimester (P < 0.0001) level and the control group (P = 0.0002). This study establishes the reference range for FXIII activity during the three trimesters of normal pregnancy and immediate postnatal period. Women have a significantly decreased level of FXIII activity during a normal uneventful pregnancy.

A comparative evaluation of a new automated assay for von Willebrand factor activity.

The ristocetin cofactor assay (VWF:RCo) is the reference method for assessing von Willebrand factor (VWF) activity in the diagnosis of von Willebrand's Disease (VWD). However, the assay suffers from poor reproducibility and sensitivity at low levels of VWF and is labour intensive. We have undertaken an evaluation of a new immunoturbidimetric VWF activity (VWF:Ac) assay (INNOVANCE(®) VWF Ac. Siemens Healthcare Diagnostics, Marburg, Germany) relative to an established platelet-based VWF:RCo method. Samples from 50 healthy normal subjects, 80 patients with VWD and 50 samples that exhibited 'HIL' (i.e. Haemolysis, Icterus or Lipaemia) were studied. VWF:Ac, VWF:RCo and VWF:Ag were performed on a CS-analyser (Sysmex UK Ltd, Milton Keynes, UK), all reagents were from Siemens Healthcare Diagnostics. The VWF:Ac assay, gave low intra- and inter-assay imprecision (over a 31-day period, n = 200 replicate readings) using commercial normal (Mean 96.2 IU dL(-1), CV < 3.0%) and pathological (Mean 36.1 IU dL(-1), CV < 3.5%) control plasmas. The normal and clinical samples exhibited good correlation between VWF:RCo (range 3-753 IU dL(-1)) and VWF:Ac (rs = 0.97, P < 0.0001), with a mean bias of 5.6 IU dL(-1). Ratios of VWF:Ac and VWF:RCo to VWF:Ag in the VWD samples were comparable, although VWF:Ac had a superior lower level of detection to that of VWF:RCo (3% and 5% respectively). A subset (n = 97) of VWD and HIL samples were analysed for VWF:Ac at two different dilutions to assess the effect on relative potency, no significant difference was observed (P = 0.111). The INNOVANCE(®) VWF Ac assay was shown to be reliable and precise.

Postpartum aHUS secondary to a genetic abnormality in factor H acquired through liver transplantation.

We report here a young female who underwent a successful deceased donor liver transplant for hepatic vein thrombosis. Five years after transplantation she developed postpartum atypical hemolytic uremic syndrome (aHUS). She did not recover renal function. Mutation screening of complement genes in her DNA did not show any abnormality. Mutation screening of DNA available from the donor showed a nonsense CFH mutation leading to factor H deficiency. Genotyping of the patient showed that she was homozygous for an aHUS CD46 at-risk haplotype. In this individual, the development of aHUS has been facilitated by the combination of a trigger (pregnancy), an acquired rare genetic variant (CFH mutation) and a common susceptibility factor (CD46 haplotype).

Evaluation of an automated platelet-based assay of ristocetin cofactor activity.

von Willebrand's disease (VWD) is regarded as the most common congenital bleeding disorder, and although not available in all laboratories von Willebrand factor (VWF) activity is most frequently assessed as ristocetin cofactor (VWF:RCo). This test can be technically challenging, is subject to poor sensitivity (∼20 IU dL(-1) VWF:RCo) and has a high degree of inter- and intra-assay imprecision [coefficient of variation (cv) > 25%]. We studied an automated assay using a combined fixed platelet/ristocetin reagent (BC von Willebrand reagent, Siemens Healthcare Diagnostics) on the CS-2000i analyser (Sysmex UK Ltd). Initially inter- and intra-assay imprecision was assessed. The automated method showed good day-to-day reproducibility and linearity of standard curves. This technique, also gave low intra- and inter-assay imprecision using commercial normal (cv < 4.5%) and pathological (cv < 8.1%) control plasmas. We then compared automated technique results from 30 healthy normal subjects and 39 VWD patients to those obtained using standard aggregometry (Bio/Data, PAP4) with lyophilised fixed platelets (Helena BioSciences) and ristocetin (American Biochemical and Pharmaceutical Ltd). The automated method had a sensitivity limit of approximately 10 IU dL(-1) vs. 20 IU dL(-1) for aggregometry. Samples giving results within the aggregometry measurable range (n = 50) exhibited good correlation with the automated technique (median 70 IU dL(-1), range 7-184 IU dL(-1); and 64 IU dL(-1), 6-138 IU dL(-1) respectively; R(2) = 0.85). We subsequently compared 3 different batches of BC von Willebrand reagent, using a second group of normal subjects and VWD patients (n = 35, 55-139 IU dL(-1) and n = 30, <10-50 IU dL(-1)). The CS-2000i results exhibited no clinically significant variation between batches (mean cv = 7%). The automated VWF:RCo assay offers a more sensitive, reproducible, robust and less laborious alternative to standard aggregometry.

The effect of prion reduction in solvent/detergent-treated plasma on haemostatic variables.

BACKGROUND: Octapharma PPGmbH has recently modified its manufacturing process for solvent/detergent-treated plasma to incorporate a prion reduction step, in which a 3 log reduction has been demonstrated. The current study was undertaken to assess the impact of this procedure on haemostatic variables in the new product OctaplasLG in comparison with standard Octaplas. METHODS: Production batches of standard Octaplas (n=4) and OctaplasLG (n=16) were assessed for levels of coagulation factors, physiological protease inhibitors, markers of activation and procoagulant microparticles. Global haemostasis was assessed by a thrombin generation test (TGT) and rotational thromboelastometry (ROTEM). RESULTS: Mean levels of factors: II, V, VII, IX, X, XI, XII and XIII, VWF:Ag, antithrombin, protein C and free protein S were all >75 u/dl. ADAMTS-13 activity levels were normal. Factor VIII and VWF:RCo were >55 u/dl. TGT and ROTEM were similar in both preparations, and microparticles were present at negligible levels. Two units of OctaplasLG had slightly elevated levels of Prothrombin Fragments 1+2, but D-Dimer and thrombin-antithrombin complexes were normal in all batches. CONCLUSION: These studies indicate that the affinity chromatography procedure used in OctaplasLG does not appear to adversely affect the proven haemostatic quality of Octaplas, while offering a selective reduction in the concentration of pathological prion proteins.

Microparticle sizing by dynamic light scattering in fresh-frozen plasma.

BACKGROUND: We have previously shown that fresh-frozen plasma (FFP) contains red blood cell-derived procoagulant microparticles (MPs) that are removable by 0.2 microm filtration. Given the limitations of current methods for accurately sizing MPs, we have applied the novel approach of dynamic light scattering (DLS) to characterize the size distributions of these MPs within FFP. METHODS: Fresh-frozen plasma was prepared from blood Group A and O donations (n = 10 of each) after an overnight hold of whole blood at 4 degrees C. On the day of analysis, plasma was thawed to 37 degrees C and daughter aliquots were studied pre- and post-filtration (0.2 microm filtration device, Ceveron MFU-500, Technoclone). MP size and dispersity was assessed using a Zetasizer Nano S (Malvern Instruments Ltd), which employs a 173 degrees backscatter detector and an N5 Submicron Particle Size Analyser (Beckman Coulter) using multi-angle measurements (30.1 degrees , 62.6 degrees and 90 degrees ). The analysers presented MP size distribution graphically as intensity plots, mean size, standard deviation and polydispersity index. RESULTS: Of the instruments used, only the N5 utilizing a 30.1 degrees angle of measurement could detect MPs of the expected size distribution and demonstrate their removal by filtration. MPs (range of mean particle diameters: pre, 101-464 nm; post, 21-182 nm filtration) were significantly smaller post-filtration (P < 0.0001), but polydispersity index (median: pre, 0.746, post, 0.769) exhibited no significant change. There was no significant difference between the size of MPs from blood Group O (pre, 247 nm) and Group A (pre, 289 nm) samples (P = 0.44). CONCLUSION: Our data demonstrates that DLS offers a novel approach to assessing MP size and distribution, a technique that could be easily adopted as a means of assessing MPs within either FFP or other blood products.

The VWF/ADAMTS13 axis in the antiphospholipid syndrome: ADAMTS13 antibodies and ADAMTS13 dysfunction.

Autoantibodies to ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type I motif, member 13) play an important role in the development of microthrombosis in thrombotic thrombocytopenic purpura (TTP). In severe cases of antiphospholipid syndrome (APS), microthrombosis can occur similar to that seen in TTP, suggesting possible mutual pathogenic factors. However, the role of ADAMTS13 in APS is unknown. We hypothesised that aberrations in ADAMTS13 may occur in APS and evaluated ADAMTS13 and von Willebrand factor (VWF) in 68 patients with antiphospholipid antibodies (aPA) including 52 with APS. Thirty-three (49%) had IgG anti-ADAMTS13 with 12 of these patients having reduced ADAMTS13 activity, suggesting neutralising antibodies. Low ADAMTS13 activity (median 34%) was demonstrated in 22/68 (33%), all with normal ADAMTS13 antigen levels consistent with dysfunctional ADAMTS13. Reduced ADAMTS13 activity was not secondary to elevated von Willebrand factor (VWF), or increased VWF secretion (normal VWF propeptide), although a reduced VWF clearance was noted in APS. Analysis found no associations between the ADAMTS13 abnormalities and any aPA profile or thrombotic/obstetric complications, although this study was not adequately powered to address clinical associations. Nevertheless, these findings highlight that ADAMTS13 autoantibodies and ADAMTS13 dysfunction can occur in APS, and although the clinical significance remains undetermined, ADAMTS13 dysfunction may be contributory to thrombogenesis in autoimmune conditions other than TTP.

The characterization and impact of microparticles on haemostasis within fresh-frozen plasma.

BACKGROUND: We have previously demonstrated that clot formation in fresh-frozen plasma (FFP) is influenced by the presence of microparticles (MP). In this study, the cellular source(s), properties and influence of MPs on clot formation within FFP were further characterized. METHODS: Fresh-frozen plasma was prepared after an overnight hold of whole blood at 4 degrees C. We examined the effect of a 0.2 microm filtration device designed to remove cellular MPs on thrombin generation test (TGT) and Thrombelastography (TEG(R)) as well as clotting factors and physiological inhibitors: prothrombin time (PT); activated partial thromboplastin time (APTT), fibrinogen (Fg), factor VIII (FVIII), von Willebrand factor antigen (VWF:Ag), antithrombin III (AT-III) and protein C (PC). MPs were measured using a functional assay and also by flow cytometry. RESULTS: Microparticle levels by functional assay were reduced by filtration (pre- 5.11 vs. post- 4.43 nmol/l phosphatidylserine equivalent, P < 0.0001). Flow cytometry showed that the most numerous MPs were derived from red blood cells, with ~87% binding annexin V, most of which (94%) were removed by filtration. MP removal had minimal effect on the PT, APTT, Fg, VWF:Ag, AT-III or PC or FVIII, but a major effect on TGT (endogenous thrombin potential: pre- 1722 vs. post- 990 nM thrombin, P < 0.0001; peak thrombin: pre- 91 vs. post- 44 nM thrombin, P < 0.0001), which in turn reflected the changes seen in TEG(R), where post-filtration clots started forming more slowly and the rate of clot formation was reduced. CONCLUSION: These data suggest that MPs contribute towards clot formation in FFP.

The dynamics of clot formation in fresh-frozen plasma.

BACKGROUND: Factor VIII (FVIII) levels are used as a quality marker of fresh-frozen plasma (FFP); however, other clotting factors are not routinely measured. METHODS: We assessed additional haemostatic parameters and the dynamics of coagulation using Thrombelastography (TEG) and a thrombin generation test (TGT). FFP was prepared on the day of donation (Day 0) or after overnight hold at 4 degrees C (Day 1). RESULTS: Factor VIII in Day 1 FFP was 18% lower than in Day 0. TEG parameters in Day 1 FFP were consistent with increased coagulability and did not correlate with altered levels of clotting factors, but were consistent with the increased levels of microparticles seen in the Day 1 samples. TGT studies exhibited increased lag time, time to peak and reduced peak thrombin generation, but no change in endogenous thrombin potential (ETP) on Day 1. There was a weak association between FVIII level and both ETP and peak thrombin (ETP r(s)> or = 0.22, P< or = 0.003; peak thrombin r(s)> or = 0.48, P< or = 0.0001), which was influenced by ABO group, with the lowest levels in group O. CONCLUSION: We conclude that levels of FVIII do not predict the haemostatic potential of FFP and that there may be a role for alternative technologies in monitoring the quality of FFP.

Antibodies against TFPI and protein C are associated with a severe thrombotic phenotype in patients with and without antiphospholipid syndrome.

BACKGROUND: Tissue factor pathway inhibitor (TFPI) antibodies, which have been reported in patients with antiphospholipid syndrome (APS), may impair TFPI activity and contribute to hypercoagulability, but their role in APS and in thrombosis remains undefined. OBJECTIVE/METHODS: We assessed the presence and avidity of TFPI IgG antibodies, associations with protein C IgG antibodies and associations with clinical disease severity, in 50 patients with thrombotic APS and 50 thrombotic control patients, on long term anticoagulation with warfarin. RESULTS: Thrombotic APS patients had a significantly higher prevalence of TFPI IgG antibodies (40%; 20/50) compared to thrombotic controls (18%; 9/50). TFPI antibodies were predominantly high avidity in APS (50%, 10/20 of positive patients) and strongly associated with a severe thrombotic phenotype (venous and arterial thromboembolism or recurrent thromboembolic episodes despite therapeutic anticoagulation) (odds ratio (OR): 12.0, 95%CI: 2.2-66.1, p = 0.004), while thrombotic control patients mainly showed low avidity antibodies (78%, 7/9 of positive patients). Coexistence of TFPI and protein C IgG antibodies, regardless of their avidity, was strongly associated with a more severe thrombotic phenotype in APS patients (OR: 20.2, 95%CI: 2.0-47.0, p < 0.0001) and also in thrombotic controls (OR: 75.0, 95%CI 1.2-195, p = 0.02). CONCLUSIONS: Coexistent TFPI and protein C IgG antibodies, irrespective of their avidity, may be a useful marker for a severe thrombotic phenotype in thrombotic patients. This suggests a possibly pathophysiological relationship between the two antibodies, predisposing to thrombosis with a possibly more general role in the development of thrombotic complications.

Clostridial wound infection following reconstruction of the anterior cruciate ligament using bone-patella-bone autograft.

A 27-year-old rugby player underwent anterior cruciate ligament (ACL) reconstruction, using autograft. Postoperatively, septic arthritis was missed due to atypical presentation but diagnosed 2 days later and underwent open arthrotomy and lavage, He received antibiotics for 5 weeks. Aspirate showed clostridium perfringens. Later, extension lag was developed, which improved by arthroscopic excision of fibrous tissue and adhesions. The source of clostridial contamination remained a mystery. Skin preparation can be ineffective in eradicating clostridium perfringens prior to procedures. Routine prophylactic use of metronidazole would be controversial. In patients with postoperative infections, we suggest that samples should be routinely sent for anaerobic cultures.

Distress related to dental extraction for children under general anaesthesia and their parents.

AIM: The aims of this study were to observe levels of distress in children and their parents before and after extractions under general anaesthesia (GA) and to assess the effect of age, gender and the number of extractions on distress. DESIGN: a randomized comparative trial. Setting University Dental Hospital of Manchester. SUBJECTS AND METHODS: Two hundred and one children, together with their parents took part in this study. Immediately before GA, the Modified Child Smiley Faces Scales (MCSFS) and Modified Adult Smiley Faces Scales (MASFS) were completed by a trained observer for children and accompanying parents respectively, and again on recovery from anaesthesia and 15 minutes postoperatively. RESULTS: There were generalised increases in mean distress scores for children when comparing the pre-operative with the postoperative scores. However, mean distress scores for parents reduced at recovery and 15 minutes postoperatively and were less than the mean distress scores for children. There was no correlation between the child and parent distress scores preoperatively, postoperatively and 15 minutes postoperatively. There were significant increase in median distress scores for younger children compared to the older children at recovery and 15 minutes postoperatively (P0.05). Children who had 8 - 14 teeth extracted demonstrated higher levels of distress than those who had 1 - 7 teeth extracted (P0.05). CONCLUSION: Extraction of teeth under general anaesthesia does produce distress in children and their parents. Child and parental distress were not related. Both age and number of teeth extracted appear to influence the level of distress in children.

Evaluation of the Sysmex XN-550, a Novel Compact Haematology analyser from the XN-L® series, compared to the XN-20 system.

INTRODUCTION: The XN-550 is a new, automated, compact, haematology analyser designed to generate a full blood count with a standard five-part white blood cell differential and an immature granulocyte count, as well as an optional reticulocyte and optical platelet (PLT) counts. The aim of the study was to evaluate the performance of the XN-550 and compare it to the established XN-20 system. METHODS: We evaluated the basic parameter and special measurement channels of the XN-550, using the XN-20 (which has a similar operating system), as a reference analyser. Precision, carry-over and throughput evaluations were performed. In addition, a total of 202 samples including normal controls and various pathological samples were studied for comparability. RESULTS: Good correlations with the reference analyser were obtained for all parameters except basophils. The XN-550 offers impedance and optical PLT counts and the latter showed a better correlation and less scatter than the impedance count and was comparable to the XN-20 fluorescent count at PLT counts ≤40×109 /L. Precision was good, and no significant carry-over was detected. CONCLUSIONS: The XN-550 was simple and easy to use, while maintaining the good diagnostic sensitivity seen with high-range systems such as the XN-20, making this compact device suitable for near-patient services and smaller satellite laboratories.

A performance evaluation of a novel human recombinant tissue factor prothrombin time reagent (Revohem™ PT).

INTRODUCTION: A new prothrombin time reagent (Revohem™ PT) based on recombinant human tissue factor produced by the silkworm-baculovirus expression system was tested. The aim of this study was to compare the performance of the new PT reagent with two widely used routine PT reagents. METHODS: All testing was performed on a Sysmex CS-5100 coagulometer. Revohem™ PT was tested for imprecision and stability using normal and abnormal lyophilized commercial control plasmas. Comparability was assessed with two widely used reagents: one containing recombinant human tissue factor (Reagent A) and the other a human placental thromboplastin (Reagent B) using a wide range of normal and abnormal plasmas and analyser-specific ISI values. RESULTS: Excellent between-day imprecision was obtained for Revohem™ PT (CV <1.0%) and acceptable open-vial on-board stability over 7 days. There was good agreement between methods in samples from patients with liver disease and patients receiving warfarin and no significant differences between methods with increasing INR values. Both recombinant reagents suffered less interference from lupus anticoagulant than the placental thromboplastin. Revohem™ PT had similar sensitivity to reagents A and B for FII, V, VII and X deficiency and demonstrated dose responsiveness to dabigatran, apixaban and rivaroxaban with steeper response curves than the comparison reagents. CONCLUSION: Revohem™ PT showed comparable or improved performance relative to two widely used reagents and is suitable for use in warfarin control, detection of inherited factor II, V, VII and X deficiency and assessment of liver disease coagulopathy.

Intraoperative local anaesthesia for paediatric postoperative oral surgery pain--a randomized controlled trial.

The aim of this study was to improve the pain experience for children following oral surgery under general anaesthesia. To this end, the efficacy and safety of intraoperative local anaesthetic (2% lidocaine with 1:200,000 epinephrine) for postoperative pain control was investigated. In a randomized controlled trial, 142 patients aged 12 years or less, who were scheduled for dental extractions under general anaesthesia, received local anaesthesia or saline intraoral injection after induction of anaesthesia. There was statistically no significant difference between groups for pain scores recorded preoperatively, on waking, at 30 min, at 24h, or for distress scores recorded preoperatively, on waking and at 30 min. 'Severe' pain scores were recorded for 13% of treatment and 12% of control patients and 'very severe' for 13% of treatment and 10% of control patients on waking. These rates were similar at 30 min but reduced at 24h. Lip/cheek biting injuries occurred in one control and three treatment patients. Intraoperative local anaesthesia has been found to be effective for pain control following a range of other surgical procedures, but we did not find it to be effective in reducing postoperative pain or distress in children after oral surgery. Reasons may include unfamiliarity with altered orofacial sensation.

Cross-sectional observational survey of serum biochemistry values in a population of 69 adult female alpacas (Vicugna pacos) in South Australia.

Blood samples were collected from 69 'healthy' female alpacas aged ≥12 months from 11 properties in South Australia. The 10-90 percentile ranges of the 16/19 analytes measured in this sample population were within the published ranges of four healthy alpaca populations from other geographic locations. Marginal exceptions were glutamate dehydrogenase and bicarbonate. Potassium was notably elevated, probably because of haemolysis of some samples. The sample size was insufficient to provide the appropriate statistical power to define diagnostic references ranges according to international standards. The health status of the sample population of alpacas was presumptive based on a physical examination.

Rivaroxaban limits complement activation compared with warfarin in antiphospholipid syndrome patients with venous thromboembolism.

Essentials Complement activation has a pathogenic role in thrombotic antiphospholipid syndrome (APS). Coagulation proteases such as factor Xa can activate complement proteins. Complement activation markers were elevated in anticoagulated thrombotic APS patients. Complement activation decreased in APS patients switching from warfarin to rivaroxaban. SUMMARY: Background Complement activation may play a major role in the pathogenesis of thrombotic antiphospholipid syndrome (APS). Coagulation proteases such as factor Xa can activate complement proteins. Aims To establish whether rivaroxaban, a direct factor Xa inhibitor, limits complement activation compared with warfarin in APS patients with previous venous thromboembolism (VTE). Methods A total of 111 APS patients with previous VTE, on warfarin target INR 2.5, had blood samples taken at baseline and at day 42 after randomization in the RAPS (Rivaroxaban in Antiphospholipid Syndrome) trial. Fifty-six patients remained on warfarin and 55 switched to rivaroxaban. Fifty-five normal controls (NC) were also studied. Markers of complement activation (C3a, C5a, terminal complement complex [SC5b-9] and Bb fragment) were assessed. Results APS patients had significantly higher complement activation markers compared with NC at both time-points irrespective of the anticoagulant. There were no differences between the two patient groups at baseline, or patients remaining on warfarin at day 42. In 55 patients randomized to rivaroxaban, C3a, C5a and SC5b-9 were lower at day 42 (median (ng mL-1 ) [confidence interval] 64 [29-125] vs. 83 [35-147], 9 [2-15] vs. 12 [4-18] and 171 [56-245] vs. 201 [66-350], respectively) but levels of Bb fragment were unchanged. There were no correlations between rivaroxaban levels and complement activation markers. Conclusions APS patients with previous VTE on warfarin exhibit increased complement activation, which is likely to occur via the classical pathway and is decreased by rivaroxaban administration. Rivaroxaban may therefore potentially provide an additional benefit to its anticoagulant effect in this patient group by limiting complement activation.

The expression of prion protein (PrP(C)) in the megakaryocyte lineage.

BACKGROUND: Cellular prion protein (PrP(C)) is a naturally occurring protein in normal individuals which adopts an abnormal conformation, termed scrapie prion protein (PrP(Sc)) that is associated with disease. There is great concern that clinically asymptomatic variant Creutzfeldt-Jacob disease (vCJD) may transmit PrP(Sc) in blood transfusion products. PrP(C) is widely expressed and has been found in human blood. The majority of cellular borne PrP(C) is associated with platelets (84%). Although PrP(C) mRNA has been demonstrated in platelets, the quantity is unknown and may not reflect the total PrP(C) present. OBJECTIVE: To investigate the expression of PrP(C) in the megakaryocyte lineage. METHODS: The expression of PrP(C) was studied in CD34+ cells, cultured megakaryocytes and platelets using electron microscopy, flow cytometry, semi-quantitative RT-PCR and immunofluorescence confocal microscopy. RESULTS AND CONCLUSIONS: The expression of PrP(C) appeared to increase with differentiation and polyploidization in the megakaryocyte lineage. PrP(C) was located within platelet alpha-granules and its source is likely to be from megakaryocyte precursors. If PrP(Sc) has a similar distribution, these results have implications for the selection of blood donors and preparation of cell-depleted blood products.