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L Poller - One of the best experts on this subject based on the ideXlab platform.

  • J Clin Pathol 1989;42:97-100 Effect of automation on prothrombin time test in NEQAS surveys
    2016
    Co-Authors: L Poller, J M Thomson, D Taberner The A Ukreferencelaboratoryforanticoagulant
    Abstract:

    were sufficient data for analysis for eight types of Coagulometer used with a single type of thromboplastin reagent and one instrument with an alternative reagent. The overall reliability efficacy ofeach instrument was evaluated by determining the orthogonal regression slope parameters for prothrombin time (PT) and international normalised ratios (INR) using the manual technique as the reference method. Seven of the eight types of Coagulometer tended to overestimate the INR. A pattern frequently observed with Coagulometers, and difficult to regulate, was a trend to underestimate INR below 3-0 and overestimate higher INR. Overestimation ofINR values over 3-0 was particularly pronounced with three types of instrument (Fibrintimer, Lancer, KC4/10). The KC4/10 was used by a sufficient number of participants to permit analysis of the performance of individual instruments. Within instrument differences were similar to those produced by different types of Coagulometers. Thromboplastin reagents affected the INR values obtained with Coagulometers. The study indicates that each local reagent-instrument combination must be calibrated by the participant to obtain reliable INR values. The use ofa general correction factor for a local PT system seems to be invalid owing to the considerable variation in performance of individual Coagulometers

  • Coagulometer international sensitivity index isi derivation a rapid method using the prothrombin time international normalized ratio pt inr line a multicenter study
    Journal of Thrombosis and Haemostasis, 2012
    Co-Authors: L Poller, Saied Ibrahim, Jorgen Jespersen, Albert Pattison
    Abstract:

    BACKGROUND: The original WHO procedure for prothrombin time (PT) standardization has been almost entirely abandoned because of the universal use of PT Coagulometers. These often give different international normalized ratio (INR) results from the manual method, between individual makes of instruments and with instruments from the same manufacture. METHOD: A simple procedure is required to derive local INR with Coagulometers. The PT/INR Line method has recently been developed using five European Concerted Action on Anticoagulation (ECAA) certified plasmas to derive local INR. This procedure has been modified to derive a Coagulometer PT/INR Line providing International Sensitivity Index (ISI) and mean normal PT (MNPT) for Coagulometers and give local INR. Results have been compared with conventional ISI calibrations at the same laboratories. RESULTS: With human thromboplastins, mean ISI by local calibration was 0.93 (range: 0.77-1.16). With the PT/INR Line, mean Coagulometer ISI was higher, for example 0.99 (0.84-1.23) but using the PT/INR Line derived MNPT there was no difference in local INR. Between-centre INR variation of a certified validation plasma was reduced with human and bovine reagents after correction with local ISI calibrations and the PT/INR Line. CONCLUSION: The PT/INR Line-ISI with its derived MNPT is shown to provide reliable local INR with the 13 different reagent/Coagulometer combinations at the 28 centres in this international study.

  • reliability of point of care prothrombin time testing in a community clinic a randomized crossover comparison with hospital laboratory testing
    British Journal of Haematology, 2002
    Co-Authors: C Shiach, Bonnie Campbell, L Poller, M Keown, N Chauhan
    Abstract:

    The success in achieving therapeutic international normalized ratio (INR) targets in the control of warfarin using a whole-blood point-of-care testing (POCT) monitor (CoaguChek) in a community clinic was compared with hospital laboratory Coagulometer prothrombin time (PT) testing in a randomized crossover study. Forty-six patients were randomized into two groups. At each visit, capillary blood was taken for the POCT monitor and venous blood for the laboratory Coagulometer. In Group 1, for 6 months, dosage was based on the CoaguChek and for the second 6 months on the Coagulometer. In the second group, the order was reversed. Dosages were determined using the dawn ac computer programme. Success was assessed by the percentage of time patients were maintained within the INR targets. Agreement between laboratory and monitor INR, and patient satisfaction were also assessed. Results with the POCT monitor compared well with the hospital Coagulometer. Time in INR target range between the groups was similar, with 60.9% on the POCT monitor and 59.3% with the laboratory Coagulometer in Group 1 and in Group 2, respectively, 64.3% and 63.4% with no significant difference in mean INR. An INR above 4.0 gave some discrepant results. International Sensitivity Index calibrations of the two test systems indicated that the INRs were dependable. Patient questionnaires showed greater satisfaction with community POCT monitoring.

  • the european concerted action on anticoagulation ecaa field studies of Coagulometer effects on the isi of ecaa thromboplastins
    Thrombosis and Haemostasis, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, J Jespersen, A Tripodi, D Houghton
    Abstract:

    Local calibration studies have been performed with lyophilized plasmas at 155 European laboratories to assess Coagulometer effects on manual ISI of ECAA thromboplastins (low ISI human recombinant and high ISI rabbit brain). Common sets of 7 normal and 20 artificially depleted lyophilized plasmas were tested with the thromboplastins in the routine local Coagulometers. With the human reagent, marked lowering of the manual ISI resulted with most Coagulometers, which was associated with disproportionate shortening of the normals. Where this shortening did not occur, there was little Coagulometer effect on the ISI. With the rabbit reagent, proportionate shortening with both normal and abnormal plasmas occurred in most instruments with little effect on ISI. INR correction by local ISI assignment appeared successful with the ECAA human reagent. There was negligible INR correction from local calibration of the ECAA rabbit reagent in Coagulometers where thromboplastin ISI were unchanged from the ECAA established manual values.

  • a comparison of linear and orthogonal regression analysis for local inr determination in ecaa Coagulometer studies
    British Journal of Haematology, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, A Tripodi, Jorgen Jespersen, D Houghton
    Abstract:

    International sensitivity index calibrations based on the W.H.O. recommended method depend on orthogonal regression analysis. As this is not readily available in statistical packages, comparison has been made with simple linear regression analysis in a study of Coagulometer effects on the International Normalized Ratio (INR) at 155 European centres. Sets of seven lyophilized normal and 20 lyophilized artificially depleted abnormal plasmas were provided with five coumarin test plasmas and two European Concerted Action on Anticoagulation reference thromboplastins (low International Sensitivity Index (ISI) human and high ISI rabbit). Local ISI based on the artificially depleted lyophilized plasmas using conventional orthogonal regression gave good correction for local Coagulometer effects on the human reagent and minimal correction with the rabbit reagent INR. Results were considerably worse after attempts at correction using calibration based on linear regression analysis with both reagents. The results indicate that calibration of Coagulometer prothrombin time systems using simple linear regression is not appropriate.

A. M. H. P. Van Den Besselaar - One of the best experts on this subject based on the ideXlab platform.

  • Effect of magnesium contamination in evacuated blood collection tubes on the prothrombin time test and ISI calibration using recombinant human thromboplastin and different types of Coagulometer
    Thrombosis research, 2005
    Co-Authors: A. M. H. P. Van Den Besselaar, W.p.f. Rutten, E. Witteveen
    Abstract:

    Abstract The purpose of the present study was to assess the effect of two types of evacuated blood collection tube on the prothrombin time and international sensitivity index (ISI) of Recombiplastin, a recombinant human thromboplastin. Vacutainer tubes were compared with Venoject II tubes. Magnesium contamination was detected in the sodium citrate solutions contained in the Vacutainer tubes with concentrations ranging from 1.1 to 1.5 mmol/l. In contrast, magnesium ions could not be detected in the Venoject II tubes. The prothrombin ratio was decreased by contamination with magnesium ions and, hence, the ISI was increased. The magnitude of the effect of magnesium contamination on the ISI was influenced by the type of Coagulometer and increased in the order: ACL Advance (3%), ACL-300 (4%), Electra-1000 (6%). The ISI bias is transmitted to the international normalized ratio (INR). In the case of the Electra-1000, the INR bias would be approximately 6% at INR 3.0 if the two types of blood collection tubes would be used without distinction. In a secondary study, the effect of magnesium contamination on the prothrombin time was assessed with the current World Health Organization international reference preparation for recombinant human thromboplastin (rTF/95). Magnesium chloride added to patients' blood (0.2 mmol/l) induced 2.3% reduction of the INR determined with rTF/95 and the manual technique. Conclusion The magnitude of the influence of blood collection tubes contaminated with magnesium on ISI and INR determined with recombinant human thromboplastin depends on the Coagulometer.

  • the european concerted action on anticoagulation ecaa field studies of Coagulometer effects on the isi of ecaa thromboplastins
    Thrombosis and Haemostasis, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, J Jespersen, A Tripodi, D Houghton
    Abstract:

    Local calibration studies have been performed with lyophilized plasmas at 155 European laboratories to assess Coagulometer effects on manual ISI of ECAA thromboplastins (low ISI human recombinant and high ISI rabbit brain). Common sets of 7 normal and 20 artificially depleted lyophilized plasmas were tested with the thromboplastins in the routine local Coagulometers. With the human reagent, marked lowering of the manual ISI resulted with most Coagulometers, which was associated with disproportionate shortening of the normals. Where this shortening did not occur, there was little Coagulometer effect on the ISI. With the rabbit reagent, proportionate shortening with both normal and abnormal plasmas occurred in most instruments with little effect on ISI. INR correction by local ISI assignment appeared successful with the ECAA human reagent. There was negligible INR correction from local calibration of the ECAA rabbit reagent in Coagulometers where thromboplastin ISI were unchanged from the ECAA established manual values.

  • a comparison of linear and orthogonal regression analysis for local inr determination in ecaa Coagulometer studies
    British Journal of Haematology, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, A Tripodi, Jorgen Jespersen, D Houghton
    Abstract:

    International sensitivity index calibrations based on the W.H.O. recommended method depend on orthogonal regression analysis. As this is not readily available in statistical packages, comparison has been made with simple linear regression analysis in a study of Coagulometer effects on the International Normalized Ratio (INR) at 155 European centres. Sets of seven lyophilized normal and 20 lyophilized artificially depleted abnormal plasmas were provided with five coumarin test plasmas and two European Concerted Action on Anticoagulation reference thromboplastins (low International Sensitivity Index (ISI) human and high ISI rabbit). Local ISI based on the artificially depleted lyophilized plasmas using conventional orthogonal regression gave good correction for local Coagulometer effects on the human reagent and minimal correction with the rabbit reagent INR. Results were considerably worse after attempts at correction using calibration based on linear regression analysis with both reagents. The results indicate that calibration of Coagulometer prothrombin time systems using simple linear regression is not appropriate.

  • the european concerted action on anticoagulation ecaa evaluation of a set of lyophilized normal plasmas to establish the normal prothrombin time for Coagulometer systems
    Thrombosis and Haemostasis, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, A Tripodi, Jorgen Jespersen, T W Barrowcliffe, D Houghton
    Abstract:

    Establishing the mean normal prothrombin time (MNPT) from fresh samples for prothrombin ratios and INR often presents difficulty in selection and collection of donors. A set of seven lyophilized normal plasmas has therefore been prepared at the ECAA Central Facility and studied at 143 laboratories in sixteen European states using Coagulometers in serial field exercises. All centres tested either the high ISI ECAA rabbit or low ISI ECAA human reference thromboplastin. The MNPT of fresh plasmas and means of the lyophilized samples were closely comparable with most routine rabbit thromboplastins. Using human thromboplastins means with the lyophilized normals were marginally but significantly longer and with the bovine Thrombotest significantly shorter than the MNPT of fresh plasmas causing alterations in INR. There was no appreciable effect on INR of 2.5 and 3.5 when lyophilized normals were substituted for fresh normals with the rabbit reagents.

  • multicentre evaluation of the thrombotest international sensitivity index used with a steel ball Coagulometer
    Journal of Clinical Pathology, 1996
    Co-Authors: A. M. H. P. Van Den Besselaar, R H M Peters
    Abstract:

    AIM: To compare the International Sensitivity Index (ISI) of the Thrombotest reagent used with a steel ball Coagulometer (KC) to the ISI of the same reagent used with the manual (tilt tube) technique. METHODS: The study was carried out by eight laboratories using their own KC instrument and method of testing. All laboratories used the same batch of Thrombotest to determine the clotting times of fresh blood samples from 20 local healthy volunteers and 60 patients on long term oral anticoagulant therapy. KC clotting times were plotted against manual clotting times on double logarithmic scales. Orthogonal regression lines were calculated to assess the ISI. RESULTS: In two laboratories the ISI of the KC method was lower than that of the manual method; these differences, however, were 2% or less. In the other laboratories no clinically important differences were observed between ISI values obtained. However, the clotting times determined with the KC methods were shorter than the manual values. CONCLUSIONS: The ISI of Thrombotest determined with the KC methods was very similar to the manual value. Therefore, use of the ISI value supplied by the manufacturer without adjustment is justified. The mean normal prothrombin time, however, must be determined locally.

D Houghton - One of the best experts on this subject based on the ideXlab platform.

  • the european concerted action on anticoagulation ecaa field studies of Coagulometer effects on the isi of ecaa thromboplastins
    Thrombosis and Haemostasis, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, J Jespersen, A Tripodi, D Houghton
    Abstract:

    Local calibration studies have been performed with lyophilized plasmas at 155 European laboratories to assess Coagulometer effects on manual ISI of ECAA thromboplastins (low ISI human recombinant and high ISI rabbit brain). Common sets of 7 normal and 20 artificially depleted lyophilized plasmas were tested with the thromboplastins in the routine local Coagulometers. With the human reagent, marked lowering of the manual ISI resulted with most Coagulometers, which was associated with disproportionate shortening of the normals. Where this shortening did not occur, there was little Coagulometer effect on the ISI. With the rabbit reagent, proportionate shortening with both normal and abnormal plasmas occurred in most instruments with little effect on ISI. INR correction by local ISI assignment appeared successful with the ECAA human reagent. There was negligible INR correction from local calibration of the ECAA rabbit reagent in Coagulometers where thromboplastin ISI were unchanged from the ECAA established manual values.

  • a comparison of linear and orthogonal regression analysis for local inr determination in ecaa Coagulometer studies
    British Journal of Haematology, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, A Tripodi, Jorgen Jespersen, D Houghton
    Abstract:

    International sensitivity index calibrations based on the W.H.O. recommended method depend on orthogonal regression analysis. As this is not readily available in statistical packages, comparison has been made with simple linear regression analysis in a study of Coagulometer effects on the International Normalized Ratio (INR) at 155 European centres. Sets of seven lyophilized normal and 20 lyophilized artificially depleted abnormal plasmas were provided with five coumarin test plasmas and two European Concerted Action on Anticoagulation reference thromboplastins (low International Sensitivity Index (ISI) human and high ISI rabbit). Local ISI based on the artificially depleted lyophilized plasmas using conventional orthogonal regression gave good correction for local Coagulometer effects on the human reagent and minimal correction with the rabbit reagent INR. Results were considerably worse after attempts at correction using calibration based on linear regression analysis with both reagents. The results indicate that calibration of Coagulometer prothrombin time systems using simple linear regression is not appropriate.

  • the european concerted action on anticoagulation ecaa evaluation of a set of lyophilized normal plasmas to establish the normal prothrombin time for Coagulometer systems
    Thrombosis and Haemostasis, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, A Tripodi, Jorgen Jespersen, T W Barrowcliffe, D Houghton
    Abstract:

    Establishing the mean normal prothrombin time (MNPT) from fresh samples for prothrombin ratios and INR often presents difficulty in selection and collection of donors. A set of seven lyophilized normal plasmas has therefore been prepared at the ECAA Central Facility and studied at 143 laboratories in sixteen European states using Coagulometers in serial field exercises. All centres tested either the high ISI ECAA rabbit or low ISI ECAA human reference thromboplastin. The MNPT of fresh plasmas and means of the lyophilized samples were closely comparable with most routine rabbit thromboplastins. Using human thromboplastins means with the lyophilized normals were marginally but significantly longer and with the bovine Thrombotest significantly shorter than the MNPT of fresh plasmas causing alterations in INR. There was no appreciable effect on INR of 2.5 and 3.5 when lyophilized normals were substituted for fresh normals with the rabbit reagents.

Jorgen Jespersen - One of the best experts on this subject based on the ideXlab platform.

  • Coagulometer international sensitivity index isi derivation a rapid method using the prothrombin time international normalized ratio pt inr line a multicenter study
    Journal of Thrombosis and Haemostasis, 2012
    Co-Authors: L Poller, Saied Ibrahim, Jorgen Jespersen, Albert Pattison
    Abstract:

    BACKGROUND: The original WHO procedure for prothrombin time (PT) standardization has been almost entirely abandoned because of the universal use of PT Coagulometers. These often give different international normalized ratio (INR) results from the manual method, between individual makes of instruments and with instruments from the same manufacture. METHOD: A simple procedure is required to derive local INR with Coagulometers. The PT/INR Line method has recently been developed using five European Concerted Action on Anticoagulation (ECAA) certified plasmas to derive local INR. This procedure has been modified to derive a Coagulometer PT/INR Line providing International Sensitivity Index (ISI) and mean normal PT (MNPT) for Coagulometers and give local INR. Results have been compared with conventional ISI calibrations at the same laboratories. RESULTS: With human thromboplastins, mean ISI by local calibration was 0.93 (range: 0.77-1.16). With the PT/INR Line, mean Coagulometer ISI was higher, for example 0.99 (0.84-1.23) but using the PT/INR Line derived MNPT there was no difference in local INR. Between-centre INR variation of a certified validation plasma was reduced with human and bovine reagents after correction with local ISI calibrations and the PT/INR Line. CONCLUSION: The PT/INR Line-ISI with its derived MNPT is shown to provide reliable local INR with the 13 different reagent/Coagulometer combinations at the 28 centres in this international study.

  • a comparison of linear and orthogonal regression analysis for local inr determination in ecaa Coagulometer studies
    British Journal of Haematology, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, A Tripodi, Jorgen Jespersen, D Houghton
    Abstract:

    International sensitivity index calibrations based on the W.H.O. recommended method depend on orthogonal regression analysis. As this is not readily available in statistical packages, comparison has been made with simple linear regression analysis in a study of Coagulometer effects on the International Normalized Ratio (INR) at 155 European centres. Sets of seven lyophilized normal and 20 lyophilized artificially depleted abnormal plasmas were provided with five coumarin test plasmas and two European Concerted Action on Anticoagulation reference thromboplastins (low International Sensitivity Index (ISI) human and high ISI rabbit). Local ISI based on the artificially depleted lyophilized plasmas using conventional orthogonal regression gave good correction for local Coagulometer effects on the human reagent and minimal correction with the rabbit reagent INR. Results were considerably worse after attempts at correction using calibration based on linear regression analysis with both reagents. The results indicate that calibration of Coagulometer prothrombin time systems using simple linear regression is not appropriate.

  • the european concerted action on anticoagulation ecaa evaluation of a set of lyophilized normal plasmas to establish the normal prothrombin time for Coagulometer systems
    Thrombosis and Haemostasis, 1998
    Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, A Tripodi, Jorgen Jespersen, T W Barrowcliffe, D Houghton
    Abstract:

    Establishing the mean normal prothrombin time (MNPT) from fresh samples for prothrombin ratios and INR often presents difficulty in selection and collection of donors. A set of seven lyophilized normal plasmas has therefore been prepared at the ECAA Central Facility and studied at 143 laboratories in sixteen European states using Coagulometers in serial field exercises. All centres tested either the high ISI ECAA rabbit or low ISI ECAA human reference thromboplastin. The MNPT of fresh plasmas and means of the lyophilized samples were closely comparable with most routine rabbit thromboplastins. Using human thromboplastins means with the lyophilized normals were marginally but significantly longer and with the bovine Thrombotest significantly shorter than the MNPT of fresh plasmas causing alterations in INR. There was no appreciable effect on INR of 2.5 and 3.5 when lyophilized normals were substituted for fresh normals with the rabbit reagents.

Michael J Hasenkam - One of the best experts on this subject based on the ideXlab platform.