BSHT and UKHCDO Programme, October 2009

P01. A comparison of techniques to measure resistance to activated protein C (APCR) P. F. Burt, P. M. Baker, & D. M. Keeling Oxford Haemophilia and Thrombosis Centre, Churchill Hospital, Old Road, Oxford, OX3 7LJ, UK Automated techniques used to measure resistance to activated protein C (APCr) are now commonly available as part of routine thrombophilia screening. We compared our current APTT based APCr screening technique (diluted in factor V deficient plasma, Coatest APCr-V, Quadratech, Surrey, UK) with two other techniques. One initiated with purified factor Xa (Hemoclot FV-L, Hyphen BioMed, Quadratech, UK) and the other snake venom (Staclot APC-R, Diagnostica Stago, Asnieres, France). All assays were performed on the Stago STA Evolution analyser. Samples from patients known to posses either the hetero and homozygous factor V Leiden genotype were tested along side normal wild type individuals. In addition samples were tested to see the impact of having antiphospholipid antibodies (demonstrated with a phospholipid dependent dilute Russell Viper Venom Time, dRVVT). Acquired APC resistance has been reported as attributable to high FVIII and low FV levels. For this reason we also tested the assays against artificially prepared samples with a range of FVIII and FV levels. Results from the individual FV Leiden haplotypes showed clear differentiation between wild type and heterozygous genotypes with a less clear division between hetero and homozygous genotypes. Patients positive for antiphospholipid antibodies had no effect on the results. All assays were sensitive to factor V levels although this was more apparent in the assays initiated at the FX level (Staclot APC-R and Hemoclot V-L). These assays also displayed a prolongation of their clotting times proportional to the FVIII level. This is the opposite of the Coatest APCr-V kit which showed a marked shortening of clotting times as previously reported. In conclusion the Factor X based assays show the ability to differentiate between FV Leiden genotypes similar to the APTT based methodology (even in the presence of antiphospholipid antibodies) but do not demonstrate acquired APC resistance in the presence of raised FVIII. P02. Comparison of a point of care device against current laboratory methodology using citrated and EDTA samples for the determination of D-dimers in the exclusion of venous thromboembolism P. M. Baker, S. J. Howgate, J. Atherton, & D. M. Keeling Oxford Haemophilia and Thrombosis Centre, Churchill Hospital, Old Road, Oxford, OX3 7LJ, UK With clinical examination and scoring quantitative D-dimer estimation is a routine part of diagnostic algorithms for the exclusion of venous thromboembolism (VTE). The ability to perform this in the acute setting contributes to the cost effective assessment of these patients. We evaluated a point of care device, Biosite Triage (Inverness Medical UK, Stockport, UK) for the estimation of D-dimers in both samples taken into citrate and EDTA against our routine laboratory D-dimer (Liatest D-dimer, Diagnostica Stago, Reading, UK) performed on the STA-R Evolution. With informed consent 103 consecutive patients were enrolled and D-dimers along with Wells scores and ultrasound scanning were recorded. One patient on low molecular weight heparin with a previously diagnosed deep vein thrombosis and a negative D-dimer was excluded from the data. Three patients had significantly higher results for the Stago Liatest D-dimer assay compared with the Biosite Triage machine although ultrasound scans were negative. Further investigation of these patients for anti-species antibodies is required. Using the manufacturers recommended cut offs of 500 ug/l FEU and 400 ug/l FEU for the Stago and Triage respectively sensitivity, specificity, positive and negative predictive values were calculated. These were 1.00, 0.42, 0.17, and 1.00 for the Triage machine using citrate samples, 1.00, 0.32, 0.14, and 1.00 using EDTA samples and 1.00, 0.29, 0.16, and 1.00 for the Stago Liatest assay respectively. In conclusion the Biosite Triage D-dimer assay performed on either citrate or EDTA samples was comparable to the Stago Liatest laboratory D-dimer assay when used in conjunction with clinical scoring and ultrasound for the exclusion of VTE. O07. Interactions between complement C3, factor XIII and fibrin may provide a link between inflammation and thrombosis Verena Schroeder, Victoria Polkinghorne, Kerrie A. Smith, Kristina Standeven, Peter J. Grant, & Angela M. Carter Division of Cardiovascular and Diabetes Research, Faculty of Medicine and Health, University of