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  • 1. Order onlineBuy this publication >>
    Arbring, Kerstin
    Linköping University, Department of Biomedical and Clinical Sciences, Division of Clinical Chemistry and Pharmacology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Acute Internal Medicine and Geriatrics.
    Two worlds, one goal: A Clinician’s Perspective on Laboratory Analyses in Anticoagulant Treatment2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Almost precisely a century ago, in the 1920s and 1930s, cattle bled to death in North America after being fed moldy hay containing sweet clover, the yellow Melilotus officinalis, and the white Melilotus albus. The toxic substance in the hay inhibiting blood coagulation was identified and named dicumarol. Further development resulted in warfarin, an oral anticoagulant that has been used for over 70 years and still is, even though newer direct-acting oral anticoagulants (DOACs) are mainly replacing it. For some patients, warfarin is still the drug of choice. A safe warfarin treatment needs repeated blood sample analysis (PT-INR), and with the new DOACs come new laboratory challenges. The aim of this thesis was to investigate ways laboratory methods can contribute to improving oral anticoagulant treatment. 

    Paper I explores genetic variants of the enzyme targeted by warfarin, VKORC1. The result shows that the haplotype VKORC1*2 is the most important of the VKORC1 haplotypes for warfarin dosage, with a lower dose requirement. The VKORC1*2 haplotype was also related to more unstable PT-INR levels. 

    Paper II describes a cross-section study comparing warfarin treatment control, as PT-INRs within the intended therapeutic range, in primary health care centers (PHCCs) and specialized anticoagulation clinics (ACCs). Both settings showed good therapeutic control, with at least as good therapeutic control in the PHCCs as in the ACCs. Today, almost all warfarin treatment in our region is centralized to ACCs. 

    Paper III focuses on the modification of a point-of-care PT method. A ratio of PT from two different dilutions of each patient sample was calculated and used as an indirect measure of DOAC activity. There were close correlations between the PT ratio and drug concentrations measured at the hospital laboratory. The detection level varies between DOACs and may limit its use in some situations. 

    Paper IV evaluated the MRX PT DOAC, an assay based on the PT ratio principle. It was found to be able to detect potentially interfering DOAC levels in plasma samples. Confirmatory testing is recommended, as is sensitivity improvement for the detection of specific interferences.   

    List of papers
    1. Main haplotypes and mutational analysis of vitamin K epoxide reductase (VKORC1) in a Swedish population: A retrospective analysis of case records
    Open this publication in new window or tab >>Main haplotypes and mutational analysis of vitamin K epoxide reductase (VKORC1) in a Swedish population: A retrospective analysis of case records
    Show others...
    2006 (English)In: Journal of Thrombosis and Haemostasis, ISSN 1538-7933, Vol. 4, no 8, p. 1723-1729Article in journal (Refereed) Published
    Abstract [en]

    Background: Vitamin K epoxide reductase (VKORC1) is the site of inhibition by coumarins. Several reports have shown that mutations in the gene encoding VKORC1 affect the sensitivity of the enzyme for warfarin. Recently, three main haplotypes of VKORC1; *2, *3 and *4 have been observed, that explain most of the genetic variability in warfarin dose among Caucasians.

    Objectives: We have investigated the main haplotypes of the VKORC1 gene in a Swedish population. Additional objective was to screen the studied population for mutations in the coding region of VKORC1 gene.

    Patients/methods: Warfarin doses and plasma S- and R-warfarin of 98 patients [with a target International Normalized Ratio (INR) of 2.0–3.0] have been correlated to VKORC1 haplotypes. Controls of 180 healthy individuals have also been haplotyped. Furthermore, a retrospective analysis of case records was performed to find any evidence indicating influence of VKORC1 haplotypes on warfarin response in the first 4 weeks (initiation phase) and the latest 12 months of warfarin treatment.

    Results and conclusions: Our result shows that VKORC1*2 is the most important haplotype for warfarin dosage. Patients with VKORC1*2 haplotype had more frequent visits than patients with VKORC1*3 or *4 haplotypes, higher coefficient of variation (CV) of prothrombin time-INR and higher percentage of INR values outside the therapeutic interval (i.e. 2.0–3.0) than patients with VKORC1*3 or *4 haplotypes. Also, there was a statistically significant difference in warfarin dose (P < 0.001) and R-warfarin plasma levels (P < 0.01) between VKORC1*2 and VKORC1*3 or 4 haplotypes. Patients with VKORC1*2 haplotype seem to require much lower warfarin doses than other patients.

    Keywords
    INR, VKORC1, warfarin
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14488 (URN)10.1111/j.1538-7836.2006.02039.x (DOI)
    Available from: 2007-05-21 Created: 2007-05-21 Last updated: 2023-10-31
    2. Comparison of prothrombin time (INR) results and main characteristics of patients on warfarin treatment in primary health care centers and anticoagulation clinics
    Open this publication in new window or tab >>Comparison of prothrombin time (INR) results and main characteristics of patients on warfarin treatment in primary health care centers and anticoagulation clinics
    2013 (English)In: BMC Health Services Research, E-ISSN 1472-6963, Vol. 13Article in journal (Refereed) Published
    Abstract [en]

    Background

    Oral anticoagulant therapy is used to prevent thrombosis in patients with atrial fibrillation (AF), venous thrombosis and prosthetic heart valves. The introduction of new therapies emphasizes the need to discern the best practice for the patients remaining on warfarin treatment. This study compares patient characteristics and therapeutic control in two settings managing warfarin treatment: Swedish primary health care centers (PHCC) and specialized anticoagulation clinics (ACC).

    Methods

    Prothrombin time (PT) test results reported as International Normalized Ratio (INR) were collected for five consecutive days from patients on warfarin treatment; 564 PHCC and 927 ACC patients. Therapeutic control was calculated as PT test results in relation to intended therapeutic range (TR). Mann–Whitney Rank Sum Test and Chi2 test were used for statistical comparisons.

    Results

    The PHCC patients were older than the ACC patients, 76 v. 70 years (p<0.01) with a predominance of men in both groups. The reasons for treating differed between the groups. Seventy-two percent of PHCC patients and 66% of ACC patients had a PT-INR within the intended TR (p<0.05). Men generally had better results than women (72% v. 63%, p<0.001) and particularly in the PHCC group v. the ACC group (78% v. 69%, p<0.01).

    PT-INR above intended TR was significantly more common in the ACC setting, (p<0.05), for women overall (p<0.01), for women in the PHCC setting, and for ACC men (p<0.05).

    Conclusions

    In this study both settings achieved good therapeutic control of warfarin treatment with a minor advantage for PHCC over ACC, and better results for men, especially in the PHCC setting. As patient characteristics differ between the PHCC and ACC, it is important to conduct further randomized studies to discern the best practice locally for warfarin management also after the introduction of new drugs.

    Place, publisher, year, edition, pages
    BioMed Central, 2013
    Keywords
    Oral anticoagulants, Treatment, Quality control, Warfarin
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-90753 (URN)10.1186/1472-6963-13-85 (DOI)000315994100001 ()
    Note

    Funding Agencies|Medical Research Council of Southeast Sweden (FORSS)||

    Available from: 2013-04-08 Created: 2013-04-05 Last updated: 2023-10-31Bibliographically approved
    3. A novel prothrombin time method to measure all non-vitamin K-dependent oral anticoagulants (NOACs)
    Open this publication in new window or tab >>A novel prothrombin time method to measure all non-vitamin K-dependent oral anticoagulants (NOACs)
    2017 (English)In: Upsala Journal of Medical Sciences, ISSN 0300-9734, E-ISSN 2000-1967, Vol. 122, no 3, p. 171-176Article in journal (Refereed) Published
    Abstract [en]

    Background: There is a clinical need for point-of-care (POC) methods for non-vitamin K-dependent oral anticoagulants (NOACs). We modified a routine POC procedure: Zafena’s Simple Simon™ PT-INR, a room-temperature, wet-chemistry prothrombin time method of the Owren-type.

    Methods: To either increase or decrease NOAC interference, two assay variants were devised by replacing the standard 10 µL end-to-end capillary used to add the citrated plasma sample to 200 µL of prothrombin time (PT) reagent by either a 20 µL or a 5 µL capillary. All assay variants were calibrated to show correct PT results in plasma samples from healthy and warfarin-treated persons.

    Results: For plasmas spiked with dabigatran, apixaban, or rivaroxaban, the 20 µL variant showed markedly higher PT results than the 5 µL. The effects were even more pronounced at room temperature than at +37 °C. In plasmas from patients treated with NOACs (n = 30 for each) there was a strong correlation between the PT results and the concentration of NOACs as determined by the central hospital laboratory. For the 20 µL variant the PT response of linear correlation coefficient averaged 0.90. The PT range was INR 1.1–2.1 for dabigatran and apixaban, and INR 1.1–5.0 for rivaroxaban. Using an INR ratio between the 20 µL and 5 µL variants (PTr20/5) made the NOAC assay more robust and independent of the patient sample INR value in the absence of NOAC. Detection limits were 80 µg/L for apixaban, 60 µg/L for dabigatran, and 20 µg/L for rivaroxaban.

    Conclusions: A wet-chemistry POC PT procedure was modified to measure the concentrations of three NOACs using a single reagent.

    Place, publisher, year, edition, pages
    Taylor & Francis Group, 2017
    Keywords
    Anticoagulant, apixaban, dabigatran, prothrombin time, rivaroxaban
    National Category
    Clinical Medicine
    Identifiers
    urn:nbn:se:liu:diva-141178 (URN)10.1080/03009734.2017.1370040 (DOI)000414107800003 ()28891412 (PubMedID)
    Note

    Funding agencies: county of Ostergotland research funds [LIO-609911]

    Available from: 2017-09-25 Created: 2017-09-25 Last updated: 2023-10-31
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  • 2.
    Arbring, Kerstin
    et al.
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Acute Internal Medicine.
    Chaireti, Roza
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Acute Internal Medicine.
    Janzon, Magnus
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Cardiology in Linköping.
    Uppugunduri, Srinivas
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Chemistry.
    Jansson, Kjell
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Lindahl, Tomas
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Chemistry.
    First experience of structured introduction of new oral anticoagulants in a Swedish health care district: dabigatran as an alternative to warfarin in atrial fibrillation2013Conference paper (Refereed)
  • 3.
    Arbring, Kerstin
    et al.
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Acute Internal Medicine.
    Uppugunduri, Srinivas
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Chemistry.
    Lindahl, Tomas
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Chemistry.
    Comparison of prothrombin time (INR) results and main characteristics of patients on warfarin treatment in primary health care centers and anticoagulation clinics2013In: BMC Health Services Research, E-ISSN 1472-6963, Vol. 13Article in journal (Refereed)
    Abstract [en]

    Background

    Oral anticoagulant therapy is used to prevent thrombosis in patients with atrial fibrillation (AF), venous thrombosis and prosthetic heart valves. The introduction of new therapies emphasizes the need to discern the best practice for the patients remaining on warfarin treatment. This study compares patient characteristics and therapeutic control in two settings managing warfarin treatment: Swedish primary health care centers (PHCC) and specialized anticoagulation clinics (ACC).

    Methods

    Prothrombin time (PT) test results reported as International Normalized Ratio (INR) were collected for five consecutive days from patients on warfarin treatment; 564 PHCC and 927 ACC patients. Therapeutic control was calculated as PT test results in relation to intended therapeutic range (TR). Mann–Whitney Rank Sum Test and Chi2 test were used for statistical comparisons.

    Results

    The PHCC patients were older than the ACC patients, 76 v. 70 years (p<0.01) with a predominance of men in both groups. The reasons for treating differed between the groups. Seventy-two percent of PHCC patients and 66% of ACC patients had a PT-INR within the intended TR (p<0.05). Men generally had better results than women (72% v. 63%, p<0.001) and particularly in the PHCC group v. the ACC group (78% v. 69%, p<0.01).

    PT-INR above intended TR was significantly more common in the ACC setting, (p<0.05), for women overall (p<0.01), for women in the PHCC setting, and for ACC men (p<0.05).

    Conclusions

    In this study both settings achieved good therapeutic control of warfarin treatment with a minor advantage for PHCC over ACC, and better results for men, especially in the PHCC setting. As patient characteristics differ between the PHCC and ACC, it is important to conduct further randomized studies to discern the best practice locally for warfarin management also after the introduction of new drugs.

    Download full text (pdf)
    fulltext
  • 4.
    Chaireti, Roza
    et al.
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Arbring, Kerstin
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences.
    Olsen, Ole H.
    Novo Nordisk A/S, Novo Nordisk Park, Måløv, Danmark.
    Persson, Egon
    Novo Nordisk A/S, Novo Nordisk Park, Måløv, Danmark.
    Lindahl, Tomas L.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Health Sciences. Linköping University, Department of Biomedicine and Surgery, Division of clinical chemistry.
    Thrombin generation and levels of factor VII activity measured in the presence of rabbit and human thromboplastins in patients with mild factor VII deficiency – effects of mutations in factor VIIManuscript (preprint) (Other academic)
    Abstract [en]

    Background/Aim: It is known that spontaneous prolonged prothrombin time-international normalized ratio may be caused by deficiency of factor VII (FVII). The activity of FVII in the presence of thromboplastins of different origin is affected by the presence of specific mutations in the F7 gene. The present study aims to evaluate patients with mild FVII deficiency and somewhat discrepant FVII activity depending on the use of human or rabbit thromboplastin in relation to mutations in the FVII gene and markers of thrombin generation.

    Patients and methods: A cohort of 10 patients with mild deficiency of FVII and discrepant FVII activity was investigated. The median ratio of the FVII activity in the presence of human/rabbit thromboplastin was 1.4. All but 1 patient had mild to no bleeding symptoms. A genetic analysis of the F7 gene was performed. Thrombin generation was measured by the calibrated automated thrombogram in platelet poor plasma in the presence of human recombinant and different dilutions of rabbit thromboplastin and compared with thrombin generation in healthy controls (n=12). Thrombin generation was measured in 9 patients as 1 was treated with warfarin at the time of the blood sampling.

    Results: Six previously described mutations were found. Two of those (FVII Padua and FVII Shinjo) are known to affect the results for FVII activity dependent on the species origin of the thromboplastin. Nine out of 10 patients had one mutation in common (Arg353Gln), which however does not affect the binding site of FVII to tissue factor. Lagtime and ttpeak increased with decreasing concentrations of thromboplastin and total and maximum thrombin concentrations increased with increasing thromboplastin concentrations in the patients with FVII deficiency. ETP in patients with FVII deficiency was 86% of ETP in controls.

    Discussion: The Arg353Gln mutation was very common, however it does not appear to affect the reactivity towards thromboplastins of different origins. Although ETP was higher in the healthy controls, thrombin generation in FVII deficient patients was enough to sustain normal haemostasis. The expected thrombin generation patterns with increasing thromboplastin concentrations were confirmed for the patients in this study.

  • 5.
    Lindahl, Tomas
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Chemistry.
    Arbring, Kerstin
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Acute Internal Medicine and Geriatrics.
    Wallstedt, Maria
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Rånby, Mats
    Zafena AB, Borensberg, Sweden.
    A novel prothrombin time method to measure all non-vitamin K-dependent oral anticoagulants (NOACs)2017In: Upsala Journal of Medical Sciences, ISSN 0300-9734, E-ISSN 2000-1967, Vol. 122, no 3, p. 171-176Article in journal (Refereed)
    Abstract [en]

    Background: There is a clinical need for point-of-care (POC) methods for non-vitamin K-dependent oral anticoagulants (NOACs). We modified a routine POC procedure: Zafena’s Simple Simon™ PT-INR, a room-temperature, wet-chemistry prothrombin time method of the Owren-type.

    Methods: To either increase or decrease NOAC interference, two assay variants were devised by replacing the standard 10 µL end-to-end capillary used to add the citrated plasma sample to 200 µL of prothrombin time (PT) reagent by either a 20 µL or a 5 µL capillary. All assay variants were calibrated to show correct PT results in plasma samples from healthy and warfarin-treated persons.

    Results: For plasmas spiked with dabigatran, apixaban, or rivaroxaban, the 20 µL variant showed markedly higher PT results than the 5 µL. The effects were even more pronounced at room temperature than at +37 °C. In plasmas from patients treated with NOACs (n = 30 for each) there was a strong correlation between the PT results and the concentration of NOACs as determined by the central hospital laboratory. For the 20 µL variant the PT response of linear correlation coefficient averaged 0.90. The PT range was INR 1.1–2.1 for dabigatran and apixaban, and INR 1.1–5.0 for rivaroxaban. Using an INR ratio between the 20 µL and 5 µL variants (PTr20/5) made the NOAC assay more robust and independent of the patient sample INR value in the absence of NOAC. Detection limits were 80 µg/L for apixaban, 60 µg/L for dabigatran, and 20 µg/L for rivaroxaban.

    Conclusions: A wet-chemistry POC PT procedure was modified to measure the concentrations of three NOACs using a single reagent.

    Download full text (pdf)
    fulltext
  • 6.
    Nelson, Nina
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Pediatrics . Östergötlands Läns Landsting, Centre of Paediatrics and Gynecology and Obstetrics, Department of Paediatrics in Linköping.
    Arbring, Kerstin
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Internal Medicine .
    Theodorsson, Elvar
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry.
    Neonatal salivary cortisol in response to heelstick: Method modifications enable analysis of low concentrations and small sample volumes2001In: Scandinavian Journal of Clinical and Laboratory Investigation, ISSN 0036-5513, E-ISSN 1502-7686, Vol. 61, no 4, p. 287-291Article in journal (Refereed)
    Abstract [en]

    Measuring cortisol in saliva offers important advantages compared to measurement in plasma or serum. However, the sampling procedure and also the detection limit cause problems, especially in paediatric and neonatal care. We describe a simple and efficient sampling procedure, together with a modification of a radioimmunoassay, which enables analysis of low (down to 1 nmol/L) concentrations of salivary cortisol (10 times lower detection limit than in the original procedure). This setting was used in studying salivary cortisol concentrations before and after heelstick on healthy newborn infants. A significant rise (median 81%, p <0.01) in salivary cortisol as response to this invasive stressor was noted.

  • 7.
    Osman, Abdimajid
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Arbring, Kerstin
    Linköping University, Department of Medicine and Health Sciences, Internal Medicine . Linköping University, Faculty of Health Sciences.
    Lindahl, Tomas
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    A new high-performance liquid chromatographic method for determination of warfarin enantiomers.2005In: Journal of Chromatography B, ISSN 1570-0232, Vol. 826, no 1-2, p. 75-80Article in journal (Refereed)
    Abstract [en]

    Warfarin is the most common agent used for control and prevention of venous as well as arterial thromboembolism. Although warfarin is administered as a racemic mixture of two stereoisomers (S and R), the S-form is mainly responsible for the anticoagulant effect. The anticoagulant effect of the drug is monitored by analysis of prothrombin complex (International Normalised Ratio,INR). In some cases, however, the measurements of plasma warfarin concentration are needed. Here, we present a new, rapid, sensitive and cost-effective HPLC-method for the determination of warfarin enantiomers in plasma. The chromatographic system consisted of Waters 616 gradient pump, Waters 996 photo diode array detector, Gilson 230 autoinjector and Pirkle (R,R) Whelk-O1 column (25 cm × 4.6 mm I.D., 5 μm). An isocratic mobile phase of methanol/acetonitrile/water (50/10/40, v/v) with 0.1% glacial acetic acid was used. The follow rate was 1 mL/min. Data analysis was carried out with Waters Millennium32. The absorbance at 305 nm was measured with a total run-time of 15 min. Method linearity was studied by establishing regression data containing eight points over the range 0.08–10 μg/mL. In this range, warfarin showed to be linear (r2 = 0.9997 for S-warfarin and r2 = 0.9998 for R-warfarin). The limit of detection in plasma was 16 ng/mL for S-warfarin and 18 ng/mL for R-warfarin. Limit of quatitation was defined as 10 × LOD. The extraction recovery was approximately 80%. Also the relation between INR and warfarin concentration was investigated. As expected, there was a low correlation between these two variables (r = 0.23, y = 0.3044x + 0.9712). This method offers a rapid and cost-effective determination of warfarin enantiomers in human plasma.

  • 8.
    Osman, Abdimajid
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Enström, Camilla
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Arbring, Kerstin
    Linköping University, Department of Medicine and Health Sciences, Internal Medicine . Linköping University, Faculty of Health Sciences.
    Söderkvist, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Lindahl, Tomas
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Main haplotypes and mutational analysis of vitamin K epoxide reductase (VKORC1) in a Swedish population: A retrospective analysis of case records2006In: Journal of Thrombosis and Haemostasis, ISSN 1538-7933, Vol. 4, no 8, p. 1723-1729Article in journal (Refereed)
    Abstract [en]

    Background: Vitamin K epoxide reductase (VKORC1) is the site of inhibition by coumarins. Several reports have shown that mutations in the gene encoding VKORC1 affect the sensitivity of the enzyme for warfarin. Recently, three main haplotypes of VKORC1; *2, *3 and *4 have been observed, that explain most of the genetic variability in warfarin dose among Caucasians.

    Objectives: We have investigated the main haplotypes of the VKORC1 gene in a Swedish population. Additional objective was to screen the studied population for mutations in the coding region of VKORC1 gene.

    Patients/methods: Warfarin doses and plasma S- and R-warfarin of 98 patients [with a target International Normalized Ratio (INR) of 2.0–3.0] have been correlated to VKORC1 haplotypes. Controls of 180 healthy individuals have also been haplotyped. Furthermore, a retrospective analysis of case records was performed to find any evidence indicating influence of VKORC1 haplotypes on warfarin response in the first 4 weeks (initiation phase) and the latest 12 months of warfarin treatment.

    Results and conclusions: Our result shows that VKORC1*2 is the most important haplotype for warfarin dosage. Patients with VKORC1*2 haplotype had more frequent visits than patients with VKORC1*3 or *4 haplotypes, higher coefficient of variation (CV) of prothrombin time-INR and higher percentage of INR values outside the therapeutic interval (i.e. 2.0–3.0) than patients with VKORC1*3 or *4 haplotypes. Also, there was a statistically significant difference in warfarin dose (P < 0.001) and R-warfarin plasma levels (P < 0.01) between VKORC1*2 and VKORC1*3 or 4 haplotypes. Patients with VKORC1*2 haplotype seem to require much lower warfarin doses than other patients.

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