Point-of-care (POCT) prothrombin time monitors: is a periodical control of their performance useful?

Introduction

Point-of-care testing (POCT) prothrombin time monitors are now widely used to monitor oral anticoagulant treatment. Although portable coagulometers are extremely easy to use, checking the quality of their performance presents some difficulties.

Materials and Methods

The aims of this study were to investigate on a quarterly basis the performance of 95 Coagucheck S assigned to 99 anticoagulated patients at home. This was done checking the monitors versus a reference coagulometer in the laboratory at our Thrombosis Centre (TC). The other aims were to carry out an external quality assessment employing different sets of INR certified plasmas with 5 different ranges of anticoagulation and to assess the performance of the different lots of strips employed by the patients during the study.

Results

No difference between the PT INR obtained with both the systems at the first quarterly check was noted but a significant difference was found when the two systems were compared at the second and third quarterly checks. The Bland-Altman test showed increased disagreement between the first and the third controls. The percentage of INR values that showed a difference of more or less than 0.5 INR units in the PT values performed with both the systems was: 1.0% (first control), 7.5% (second control) and 11.5% (third control) (Chi-Square: 8.315, p = 0.0156). Lots with differences higher than 10% in terms of ± 0.5 INR Units at the first, second and third controls were 16%, 20.8% and 61%, respectively. Seven monitors (7.3%) failed to test one or two of the INR certified plasmas of one set but performed well using a second set of plasmas. Three monitors (3.1%) failed to test two sets of plasmas but performed well using a different lot of strips (from 279A to 483A). One monitor (1%) gave unsatisfactory results with different sets of plasmas and strips. All the other PT INR obtained with the monitors fell well within the different ranges of the INR certified plasmas.

Conclusions

Anticoagulated patient in self-testing or self-management should periodically bring their portable coagulometer to a reference Thrombosis Centre especially when the lot of strips have to be changed. The role of Thrombosis Centre appears therefore crucial in this regard.     

A prospective controlled trial comparing weekly self-testing and self-dosing with the standard management of patients on stable oral anticoagulation

Oral anticoagulant therapy requires frequent laboratory controls of its intensity to assure therapeutic efficacy and to prevent potentially life threatening adverse events. It is generally assumed, that increasing the frequency of testing would lead to a better control of anticoagulation. We tested this hypothesis in a prospective controlled trial comparing weekly self-testing and self-dosing (self management) with the standard-management of these patients in an anticoagulation clinic. Only patients with stable anticoagulation were included into the study. We recorded 2733 weekly determinations of the intensity of anticoagulation (INR) in 49 patients on self-testing and self-dosing and 539 determinations of the INR in 53 patients on standard-management. Two intensities of anticoagulation were used in each group: a target INR of 3.5 for patients with artificial heart valves (target range: 2.5-4.5) and a target INR 2.5 (target range: 2.0-3.0) for patients with atrial fibrillation or venous thromboembolism. The deviation from the target INR, the fraction of INR determinations within the preset therapeutic range and the difference between the target INR and the actually achieved mean INR were the three major endpoints of the study. The mean deviation from the target INR was smaller in the groups of patients on self-management compared to the patients on standard-management. Individual deviations were significantly (p <0.0001) dependent on the type of management in interaction with the treatment intensity in a general linear model. Patients on weekly self-testing and self-dosing had more INR values within the therapeutic range than patients on standard-management (86.2% vs. 80.1% at INR range 2.5-4.5; 82.2 vs. 68.9 at INR range 2.0-3.0). The achieved mean INR was almost identical with the target INR in the patients on self-management but was significantly (p <0.005) below the target INR in the high intensity anticoagulation group on standard-management (target INR:3.5; achieved mean INR: 3.19; CI 0.95: 3.05-3.34). Our data show, that weekly self-testing and self-dosing leads to a better control of anticoagulation than standard treatment in an anticoagulation clinic.     

Evaluation of frozen plasma calibrants for enhanced standardization of the international normalized ratio (INR): a multi-center study

Local ISI calibration has been proposed to improve INR accuracy and inter-laboratory precision. We evaluated the affect of local PT calibration on INR precision and accuracy using six levels of frozen plasma calibrants prepared and pooled from normal donors and patients stabilized on sodium warfarin (coumarin) based oral anticoagulant therapy (OAT). Reference prothrombin time (PT) and INR values were assigned to these calibrants in accordance with World Health Organization (WHO) procedure using rTF 95 international reference preparation (IRP) of thromboplastin (human recombinant). These calibrants, along with five similarly characterized individual OAT patient plasmas, were distributed to 127 laboratories in a multi-center study. Calibrant plasmas were evaluated and INR's subsequently determined on the 5 OAT test samples using: 1) the ISI and MNPT in place before the study (the local system), 2) the locally calibrated ISI value (local system with ISI calibration) and 3) a PT-INR calibration curve. Precision of INR results improved across the study group using the local system with ISI calibration and the PT-INR calibration curve methods, while accuracy of INR results improved using the PT-INR calibration curve approach only and not the local ISI calibration. The authors conclude that frozen plasma calibrants can be used locally to enhance precision and accuracy of PT results as reported in INR. These calibrants are effective over a range of reagents and instrument combinations. Furthermore, the PT-INR calibration curve appears to be the superior method for local calibration.     

Systematic review of studies of self-management of oral anticoagulation

This work is aimed at assessing the evidence for the possible improvement of therapeutic control of anticoagulation, reduction of major bleedings, thromboembolism and improvement of treatment-related quality of life in patients with self-managed oral anticoagulation therapy versus oral anticoagulation patients on routine care. Randomised controlled trials (RCTs) were identified using the COCHRANE LIBRARY, MEDLINE and EMBASE from 1966 to 2003. RCTs were selected involving patients with oral anticoagulation, which were designed to compare a self-management group to a routine care group. Abstracts and keywords were screened and, in the case of potential inclusion, evaluated. We identified nine potentially relevant trials. Five were excluded for the following reasons: double publication, the patients involved performed only self-testing, or the results of the trial were only published as an abstract. Ultimately, four randomised controlled studies fulfilled the criteria for inclusion. Anticoagulation control: Statistical analysis was not possible because of the great variety of international normalised ratio measurements per patient between the different studies. Comparing the four studies, there was no difference in oral anticoagulation control between self-management care and management by a specialised anticoagulation clinic. In comparison with routine care by general practitioners, self-management care was found to be better. Major bleeding, arterial and venous thromboembolism: Data were available for all studies; however, the studies were either underpowered or obviously not valid and therefore not suitable for statistical analysis. Treatment-related quality of life: Data were available for two studies, which showed that self-management could clearly improve treatment-related quality of life. Patients' self-management can improve the quality of oral anticoagulation as an indirect parameter of a reduced risk for thromboembolic and bleeding complications. Self-management oral anticoagulation treatment is safe and improves treatment-related quality of life. Patients' self-management is safe and can improve the quality of anticoagulation control, however, no valid long term study has yet actually demonstrated reduction of bleeding and thromboembolic events.     

INR comparison between the CoaguChek Pro PT(N) and a standard laboratory method

BACKGROUND: The prothrombin time (PT), also called thromboplastin time ("Quick"), is usually measured using citrated plasma from venous blood. Recently, portable coagulation monitors have been developed, which measure PT using non-anticoagulant capillary whole blood from a finger stick. In the present study, we compared the International Normalized Ratio (INR) of the standard laboratory method (INRven) with the newly developed reagent PT(N) for the CoaguChek Pro portable monitor (INRcap) in various patient groups: healthy individuals, patients with oral anticoagulation and patients with a deficiency of coagulation factor V, factor VII or factor X, respectively. METHODS: One hundred and fifty-five patients were included in this prospective open comparison study. Capillary PT was measured with the portable coagulation monitor CoaguChek Pro using the new disposable cartridge PT(N) (containing rabbit brain thromboplastin). In comparison, PT was measured using citrated venous plasma and the reagent Innovin on the coagulation analyzer STA-R. RESULTS: We found a correlation coefficient of 0.85 between capillary and venous INR values among the 100 patients with oral anticoagulation. The slope of the regression line was 1.4 and the y-intercept is -0.65. Agreement between both methods was found to be 80% (95% CI: 72-88%) and the standard-agreement was 85% (95% CI: 78-92%). Among the 30 healthy subjects, the individual differences between INRven and INRcap were in 4 cases 0, in 21 cases 0.1 and in 5 cases 0.2. CONCLUSION: The new test cartridge PT(N) was found to be a valuable tool for measuring PT among healthy subjects. However, among patients with oral anticoagulation, agreement between INRcap measured with the new cartridge PT(N) and INRven was only moderate. Our results show that improvements are necessary for a more valuable measurement of capillary PT with portable coagulation monitors.     

Self-testing and self-management of oral anticoagulation therapy in children

Children and adolescents on oral anticoagulation therapy (OAT) present special challenges in terms of rapid fluctuations in International Normalised Ratio (INR) values, interruption in daily life due to frequent hospital/doctor visits, and difficulties and pain in the performance of venepuncture. Optimised management of OAT improves the quality of treatment, potentially accomplished by new methods such as patient self-testing (PST) and patient self-management (PSM). A review was performed, identifying 11 trials with children and adolescents. All studies had different methodological problems, predominantly by being non-randomised trials. A total of 284 patients were included with a mean follow-up of 22 months, finding a time within therapeutic INR target range between 63% and 84%. The coagulometers used for estimating the INR values were found to have sufficient precision and accuracy for clinical use, but external quality control is probably advisable. It can be concluded that PST and PSM are at least as good treatment options as conventional management in highly selected children. Larger studies, preferably randomised, controlled trials using clinical endpoints, are obviously needed in order to elucidate whether these new regimens of treatment are superior to conventional management of oral anticoagulation therapy.     

A multicenter study on amidolytic factor X evaluation in oral anticoagulant therapy

For laboratory control of oral anticoagulation, amidolytic factor X (F X) determination may offer an alternative to standardization difficulties of prothrombin time (PT). In order to validate this amidolytic assay on a large scale, a multicenter study was undertaken in 6 French laboratories using the same chromogenic substrate (Stachrom X Stago) and different automated instruments. Intra and between laboratory reproducibility of factor X was estimated on fresh and lyophilized patients plasmas and was found to be highly satisfactory. Standardization of the method did not seem to depend on the chromogenic substrate used, as investigated in two different centers. Results of PT and factor X were compared in over 500 patients on a long-term stabilized oral anticoagulant treatment: there was a strong positive correlation between the 2 tests in each center. The therapeutic range for factor X was evaluated from therapeutic PT values reported by Duckert and Marbet for the different thromboplastin reagents: the estimated mean range was 21 to 32%. Pooling the results of the six different centers a concordant information for prothrombin time and factor X amidolytic assay was found in 76% of patients and a fully discordant response was present in 0.6%. The results suggest that amidolytic factor X may be suitable for monitoring long-term anticoagulation. However, prospective trials are needed to evaluate its usefulness as compared to conventional methods.     

Anticoagulation Choice and Timing in Stroke Due to Atrial Fibrillation: A Survey of US Stroke Specialists (ACT-SAFe)

ObjectiveRisk of early recurrent ischemic stroke in patients with atrial fibrillation may be high. ASA/AHA guidelines provide imprecise recommendations on the timing and anticoagulant choice for this indication. We assessed current opinions of stroke neurologists.MethodsCase scenarios describing patients with acute ischemic stroke (AIS) due to paroxysmal atrial fibrillation (AF) were presented to US board-certified stroke neurologists in an internet-based questionnaire. Questions assessed timing and choice of anticoagulation for secondary stroke prevention, factors prompting earlier anticoagulation, reasons for specific anticoagulant choice, and alternatives to anticoagulation in ineligible patients. Open-ended comments were also solicited.ResultsResponses were available from 238/1239 stroke neurologists surveyed. In patients with small AIS without hemorrhagic transformation (HT), 51% elected to start anticoagulation within 96 hours. With increased stroke severity and asymptomatic HT, only 29% and 26% respectively chose to anticoagulate within 7 days. Few requested stability imaging before starting anticoagulation. With symptomatic HT the majority (79%) waited >14 days. 93% would anticoagulate earlier if left atrium/left atrial appendage or acute left ventricular thrombi, or mechanical heart valve were present. Direct oral anticoagulants (DOACs) were the preferred anticoagulation strategy (64%), and the remaining 38% preferred Warfarin. Aspirin was preferred by 57% in anticoagulation ineligible.ConclusionApart from AIS with symptomatic HT, there is a remarkable lack of consensus among stroke neurologists regarding the timing of anticoagulation for secondary stroke prevention in patients with AIS due to PAF. DOACs are the preferred anticoagulation strategy. More studies are required to clarify anticoagulant management in this patient population.     

Long-term stability and reproducibility of CoaguChek test strips

Whole-blood point-of-care testing prothrombin time monitors are being used on an increasing scale for the monitoring of oral anticoagulant therapy. These monitors are used with disposable test strips containing tissue factor reagent. The purpose of the present study was to assess the stability of different CoaguChek-S strip lots for a period of one year. Ten strip lots introduced successively in the Netherlands were obtained from the manufacturer's representative and stored at 4-8 degrees C. Six deep-frozen pooled plasmas were analyzed for the prothrombin time and INR with the strips at six or seven occasions spread over one year. The test plasmas were recalcified immediately before application to the CoaguChek-S system. Regression analysis was performed on the clotting times obtained with each plasma. In the majority of cases (i.e.95%), no significant change was observed at the 5% significance level. A significant change was observed in only 3 cases. In addition, a ranking statistic was used as test of a monotonic relationship in the two-way analysis of variance. The results of the ranking statistic were not significant for any strip lot, indicating that the test strips were stable under these storage conditions. The reproducibility of INR measured with the CoaguChek-S was assessed. The mean within-run coefficient of variation (CV) of INR ranged from 2.58% to 3.36% (CV). The between-lot variation of the mean INR ranged from 3.2 to 4.5 % (CV). The over-all variation of single INR measurements, i.e. including between-lot and within-lot, ranged from 5.0 to 6.0 % (CV).     

INR comparison between the CoaguChek S and a standard laboratory method among patients with self-management of oral anticoagulation

INTRODUCTION: Portable coagulation monitors have been developed to measure International Normalised Ratio (INR) in orally anticoagulated patients using capillary whole blood from a finger stick. Because of unsatisfactory precision of some of the monitors in comparison with laboratory methods new devices are being developed. In the present study we compared INR determination with the CoaguChek S device with a standard laboratory method among patients with self-management of oral anticoagulation (OAC). METHODS: Two hundred and forty-two patients performing self-management of OAC were enrolled into this study. Parallel INR measurements were performed within one hour. Capillary INR measurements (INRcap) were done by the patients with the CoaguChek S and venous INR (INRven) by qualified medical staff using a standard laboratory method. RESULTS: We found a correlation coefficient (r(S)) of 0.85 (95% CI: 0.81-0.88) among the 242 patients between INRven and INRcap. In 84.4% of the INR parallel measurements the difference between the two values was below 0.5 INR units. In only 2 of 242 cases the difference was >1 INR unit (1.1 and 1.3). The slope of the Passing Bablok regression line was 0.91 (95% CI: 0.83-1.0) and the y-intercept 0.06 (95% CI: -0.20-0.25). Agreement between both methods was 90.5% (95% CI: 86.8-94.2) and standard-agreement even 97.1% (95% CI: 95-99.2). CONCLUSIONS: INR measurement with CoaguChek S device by trained patients revealed reliable results in comparison to the values obtained with a standard laboratory method.     

Herbal remedies and anticoagulant therapy

Herbal remedies, considered to be both safe and effective by most consumers, may interact with conventional drugs. Warfarin, a vitamin K antagonist originally derived from the sweet clover plant, has a narrow therapeutic window which can be monitored using prothrombin international normalized ratios (PT-INR). Many herbs can increase the risk for bleeding when combined with warfarin, either by augmenting the anticoagulant effects of the drug (with increased PT-INR levels) or through intrinsic anti-platelet properties (without altering PT-INR levels). The increased risk for bleeding among such patients may be difficult to predict, especially when formulas which contain many herbs are used. Further research into herb-drug interactions is warranted, as are guidelines for the use of herbal remedies by patients on chronic anticoagulation therapy.     

The ‘carry-over’ effects of patient self-testing: Positive effects on usual care management by an anticoagulation management service

Introduction

Patient self-testing (PST) of the international normalised ratio (INR) has a positive effect on anticoagulation control. This study investigated whether the benefits of PST (other than increased frequency of testing, e.g. patient education, empowerment, compliance etc.) could be ‘carried-over’ into usual care management after a period of home-testing has ceased.

Material and methods

Patients that completed a six month period of PST (as part of a randomised controlled trial) but returned to clinic management when the trial ended were included in the study. The primary outcome variable was the difference in anticoagulation control (measured using the time in therapeutic range) between the two periods. A group of patients who were managed solely by the anticoagulation clinic served as the control.

Results

There was no significant difference in median time in therapeutic range (TTR) between the 52 patients during clinic management post-PST and the six month period of PST (75% vs 75.3%; p = 0.061). Patients tested more frequently while home-testing compared with the subsequent six month period of clinic management (once every 5.6 ± 0.7 days compared with once every 23.2 ± 7.4 days; p = 0.000). Patients with previous experience of PST performed significantly better than the control group of patients (n = 107) that were managed solely by the anticoagulation clinic (75% vs 59.7%; p = 0.009) despite less frequent monitoring of the INR (every 23.2 ± 7.4 days vs. 17.4 ± 6.7 days; p = 0.000).

Conclusions

The improvements in anticoagulation control observed during a period of PST can be sustained when patients cease home-testing and revert back to usual care management.     

The utility of routine head CT for hemorrhage surveillance in post-craniotomy patients undergoing anticoagulation for venous thromboembolism

Anticoagulation for postoperative venous thromboembolism (VTE) may infer a higher risk of intracranial hemorrhage. We treat patients with VTE using slowly titrating intravenous heparin drip without bolus. When PTT is greater than 60 s, a head CT is obtained to monitor for the development of a intracranial hemorrhage before transition to oral anticoagulation. We evaluated the utility of routine surveillance head CT to monitor for intracranial hemorrhage during anticoagulation. This is a case series of neurosurgical patients in an academic quaternary hospital who developed a VTE after cranial procedures between 2007 and 2017. Over 11,000 patients were screened for the study. Patients’ demographics data, surgical indication, PTT at the time of surveillance CT head, surveillance CT head findings, and patient’s clinical course were reviewed. A total of 83 patients were included. Three patients (3.6%) developed a new subclinical hemorrhage on CT head imaging while on heparin drip. Interval CT head showed stable hemorrhage in all patients. Heparin drip was stopped in two patients and they both progressed from DVT to pulmonary embolism: one patient died due to cardiac arrest, the other patient was transitioned to oral anticoagulation. In the third patient heparin drip was continued uneventfully and transitioned to oral anticoagulation with no further clinical sequalae. Surveillance CT while on heparin drip for VTE management detected subclinical intracranial hemorrhage in a small subset of patients. Patients whose anticoagulation was stopped had progression of VTE. Undertreatment of VTE in the presence of subclinical hemorrhage may lead to significant morbidity and mortality.     

Prevention of brain infarction in patients with atrial fibrillation]

The patients with cardioembolic stroke sometimes suffer from severe neurological deficit and from recurrent strokes. Since atrial fibrillation, especially non-valvular atrial fibrillation (NVAF) is associated with over half of the cardioembolic strokes, the prevention of cardioembolic stroke in patients with NVAF is important. There have been some reports about how to prevent stroke. They have indicated that the best medication for preventing from stroke was anticoagulation by warfarin. Therefore, the guidelines recommended the patients with NVAF to take warfarin. In case with the older patients under 70 years, prothrombin international normalized ratio (PT-INR) should be kept from 2.0 to 3.0. On the other hand, if the patients with NVAF are over 70 years, PT-INR has to be controlled from 1.6 to 2.6. Before extraction of a tooth, anticoagulation should not be call off.     

Reasons for underuse of oral anticoagulation in atrial fibrillation-associated stroke: prospective study of German stroke patients

Oral anticoagulation in atrial fibrillation (AF) is effective in primary and secondary prevention of cardioembolic stroke, but is often underused in practice. The detailed reasons for non-use of oral anticoagulation are less well known. We prospectively analyzed 105 consecutive cases of acute ischemic stroke associated with atrial fibrillation. Patients were investigated by a semi-structured interview. The most frequent reasons for underuse were: unknown AF (43 %). In case of known AF: reluctance of patients (30 %), contraindications (25 %) and compliance problems (20 %). There was good agreement between patients and physicians views about nonuse or aborted use of oral anticoagulation (kappa 0.64 and 0.93, respectively). Unknown atrial fibrillation is the most prevalent cause of underutilization of oral anticoagulation in acute stroke patients. Since atrial fibrillation is easy to detect in most cases, it could be worthwhile to screen elderly patients without contraindications for anticoagulation.     

The quality of oral anticoagulation before,during and after a period of patient self-management

The study analyzes the quality of anticoagulation during a 3-year follow-up on patients who were treated by an anticoagulation clinic (ACS) for 1 year (Phase I), performed weekly self-management of anticoagulation (PSM) after a specific training for another year (Phase II) and finally returned to be treated by the anticoagulation clinic (ACS) for a third year (Phase III). The mean fraction of INR values within therapeutic target range was higher in Phase II (0.69 +/- 0, 11) compared to Phases I (0.40 +/- 0.20) and III (0.56 +/- 0.18; p < 0.05). Time spent in therapeutic target range was higher in Phase II (0.70 +/- 0.10) compared to Phases I (0.43 +/- 0.25) and III (0.60 +/- 0.17; p < 0.05). Mean square deviation from target value was lower in Phase II (0.39 +/- 0.17) compared to Phases I (0.81 +/- 0.44) and III (0.64 +/- 0.39, p = 0.05). Thus, the quality of anticoagulation during Phase II (PSM) was significantly better compared to Phases I (ACS) and III (ACS) in all endpoints tested. This shows that the quality of oral anticoagulation deteriorates again if patient self-management is stopped and patients return to conventional treatment. Furthermore, the quality of anticoagulation was better in Phase III (post-PSM) compared with Phase I (pre-PSM) although the type of treatment was identical in both phases (ACS). This suggests that the increased patient empowerment and enhanced compliance acquired during PSM (Phase II) might have a positive impact on the quality of anticoagulation, even when patients return to the conventional treatment (ACS).     

Oral anticoagulation for cerebral ischemia of arterial origin: high initial bleeding risk.

BACKGROUND: The use of oral anticoagulant therapy for the prevention of arterial thromboembolism in patients who have had ischemic stroke is controversial. Coumarins may increase the bleeding risk in patients with cerebral ischemia of arterial origin. OBJECTIVES: 1) To calculate incidence rates of bleeding and thromboembolic events in patients with noncardiac cerebral ischemia who were treated routinely in an anticoagulation clinic. 2) To assess which factors contribute to the occurrence of events. 3) To determine the optimal intensity of oral anticoagulant therapy in these patients. METHODS: The authors studied all patients treated for noncardiac cerebral ischemia at the Leiden anticoagulation clinic between 1993 and 1998. Outcome events were major hemorrhage, major arterial thromboembolism, and death. RESULTS: The authors observed 356 patients for 644 patient-years. The incidence of major hemorrhage was 3.9 per 100 patient-years (95% CI, 2.5 to 5.7) and that of thromboembolism was 3.0 per 100 patient-years (95% CI, 1.8 to 4.6). The incidence of hemorrhage varied with the duration of treatment (relative risk [RR] of the first versus the second half-year, 3.8; 95% CI, 1.9 to 7.6), age (RR for age >65 years, 3.7; 95% CI, 1.1 to 12.3), and the intensity of oral anticoagulation (RR, 1.8 for each 0.5 international normalized ratio [INR] unit increase; 95% CI, 1.5 to 2.3). The optimal intensity of oral anticoagulant therapy was 2.5 to 3.5 INR; the best target value was 3.0 INR. CONCLUSION: The risk of hemorrhage with anticoagulant therapy is high in patients with ischemic stroke of arterial origin but is mainly confined to early use and elderly patients.     

Calibration of local systems with lyophilized calibrant plasmas improves the interlaboratory variability of the INR in the Italian external quality assessment scheme

Calibration with lyophilized calibrant plasmas certified in terms of PT with International Reference Preparations for thromboplastin has been proposed to minimize the effect of coagulometers on the INR. Aim of this study was to test the ability of local calibration with lyophilized calibrant plasmas, combined with a modified statistical approach, to improve the interlaboratory variability of the INR measured on two test plasmas (one coumarin and one artificially-depleted) by participants in the External Quality Assessment Scheme (EQAS). Sets of lyophilized calibrant and test plasmas were sent to the participants in the EQAS, who were asked to determine PT with their own reagent/ instrument combination (local system). Results were returned as PT together with information on the type of local system, the stated International Sensitivity Index (ISI) and the geometric mean of PTs determined by testing with the local system fresh plasmas from 20 healthy subjects. Ninety-two participants using 9 and 11 brands of reagents and instruments returned results. The CV of the INR determined with the stated ISI for the coumarin (Mean INR = 4.39) and artificially-depleted (Mean INR = 4.23) test plasmas were 11.2% and 10.3% and were reduced on the average by 34% and 54%, respectively, when the INR was calculated with the local ISI. In conclusions, results from this field study involving laboratories and testing systems representative of the real situation in oral anticoagulant monitoring in our country, indicate that local calibration by artificially-depleted plasmas, combined with the proposed statistical approach, is suitable to improve the interlaboratory agreement on the INR.     

Warfarin-related outcomes in patients with antiphospholipid antibody syndrome managed in an anticoagulation clinic

Patients with antiphospholipid antibody syndrome (APA) are at elevated risk of venous and arterial thromboembolic complications. Oral anticoagulation with warfarin is recommended for secondary prevention of thromboembolism, but warfarin-related outcomes have not been systematically investigated when warfarin therapy is managed by a dedicated anticoagulation clinic. The objectives of the study were to evaluate warfarin-related monitoring outcomes, clinical endpoints and the use of healthcare resources as a result of warfarin-related complications in patients with APA compared to a group of patients without APA, all of whom were managed in an anticoagulation clinic setting. A retrospective observational cohort design was used to investigate patients with and without APA, all of whom had a history of venous or arterial thromboembolism, and were matched for age, gender and indication for oral anticoagulation. Thirty-six APA patients taking warfarin were compared to a matched cohort of 36 patients without APA. Monitoring outcomes (time in therapeutic range, clinic visits per year, frequency of warfarin dosing adjustments, reasons for out-of-range INRs) were similar between groups, as was the frequency of major bleeding complications (3.2%/pt-yr vs. 3.1%/pt-yr). However, recurrent thromboembolic events (9.6%/pt-yr vs 0) occurred more frequently in APA patients. APA patients required more emergency room visits (6.4%/pt-yr vs. 1.6%/pt-yr) and hospital admissions (14.4%/pt-yr vs.3.0%/pt-yr) to manage complications of warfarin therapy. In conclusion, despite similar monitoring outcomes obtained in a dedicated anticoagulation clinic setting, adverse clinical outcomes are significantly more frequent in patients with APA syndrome than in those without APA, and require more frequent use of healthcare resources.     

Transoesophageal echocardiography in selecting patients for anticoagulation after ischaemic stroke or transient ischaemic attack

OBJECTIVES: To investigate prospectively the role of transoesophageal echocardiography (TEE) in selecting patients for anticoagulation in an unselected stroke population. METHODS: Transthoracic echocardiography (TTE) and TEE were done in all clinically suitable hospitalised patients (n = 457) with transient ischaemic attack or ischaemic stroke in the acute phase during a two year period in Turku University Hospital. 441 patients were successfully evaluated for cardiac sources of embolism using TEE within 31 days of the event. RESULTS: A major risk factor for a cardiac source of embolism excluding atrial fibrillation, acute myocardial infarction, and prosthetic valve was detected in 10% of patients and a minor risk factor for a cardiac source of embolism in 46%. When a major risk factor of a cardiac source of embolism was detected using TTE or TEE and no contraindications were present, the patient was given anticoagulation drugs. If a minor risk factor for a cardiac source of embolism was detected, anticoagulation treatment was started after clinical assessment, if no contraindications were present. In 62 (14%) cases, the patient was given oral anticoagulation drugs or the necessity of ongoing anticoagulation treatment was confirmed on the basis of TEE. When these anticoagulation treated patients were evaluated using logistic regression analysis, they were found to have significantly more atrial fibrillation and histories of myocardial infarctions. Moreover, the patients were mainly men. When patients in sinus rhythm and without any history of cardiac disease were analysed, 8% of patients were found to have been given anticoagulation drugs on the basis of TEE data. CONCLUSION: This study suggests that TEE should be used in patients with stroke even without any clinical evidence of cardiac disease when the patients are candidates for anticoagulation.