Point-of-care International Normalized Ratio Research Articles

CoaguChek and Coag-Sense PT2 Meter Point of Care INR Device Validation

ObjectiveTo standardize international normalized ratio (INR) measurements and improve data integrity by enabling electronic result transmission for warfarin monitoring, two point-of-care (POC) devices were evaluated against an internal plasma INR reference method. MethodsA multicenter study was pursued (January 24, 2022, through October 19, 2022) to compare concordance of two commercially available POC devices, Coag-Sense PT2 Meter (Coag-Sense) and CoaguChek XS Pro and Plus devices (CoaguChek), against an internal plasma INR method among patients treated with warfarin. Bias and linear regression analysis were assessed for these devices including dosing decision accuracy compared with plasma INR reference. ResultsTwo hundred ninety-nine patients treated with warfarin across three Mayo Clinic sites agreed to participate. Atrial fibrillation (n=191, 63.9%), venous thromboembolism (n=65; 21.7%), and heart valve prosthesis (n=46; 15.4%) were common anticoagulant indications with a 2.5 INR target for 280 (93.6%) of patients. For the CoaguChek devices, 243 (81.3%) of values fell within 0.2 INR units with plasma INR referent and 285 (95.3%) within 0.4 units (R2=0.93). For the Coag-Sense device, 102 (34.1%) of values fell within 0.2 INR units and 180 (60.2%) within 0.4 INR units of plasma INR values, (R2=0.83; P<.0001). Using the plasma INR as the gold standard, appropriate dosing recommendations would have occurred for 292 (97.7%) of the CoaguChek and 244 (81.6%) of the Coag-Sense results. ConclusionCompared with a plasma referent, INR values obtained from the CoaguChek devices exhibited less systematic bias compared with Coag-Sense measures. This translates to a greater percentage of concordant management decisions between POC and laboratory INR methods.

Correlation of prehospital point-of-care international normalized ratio to laboratory-based international normalized ratio in acute traumatic coagulopathy.

Acute traumatic coagulopathy (ATC) is associated with increased mortality and hospital transfusion requirements. Accurate pre-hospital identification of ATC may improve outcomes by expediting care. Unlike clinical scores which may include subjective components, point of care (POC) international normalized ratio (INR) testing provides an objective value which in the non-trauma setting correlates well with laboratory INR (LABINR) results.The objective of this study was to evaluate the accuracy and ROC characteristics of pre-hospital sampled POC INR tests in trauma patients. Blood was drawn in the field for pre-hospital POCINR and comparative LABINR testing. Acute Traumatic Coagulopathy (ATC) was defined as LABINR31.3 and severe ATC LABINR31.5. Of 137 patients included in the analysis, ATC was present in 20 patients (14.6%) and severe ATC in six (4.7%). POCINR estimated LABINR with bias of 0.036 (95%CI: -0.297-0.369). ROC analysis for severe ATC demonstrated an AUC = 0.92 (95%CI: 0.83-1.00). Pre-hospital POCINR correlates well with for LABINR in trauma patients. It has excellent ROC characteristics for diagnosing trauma patients with an INR31.5. II/III.

A retrospective analysis of discordances between international normalized ratio (INR) self-testing and INR laboratory testing in a pediatric patient population.

The lack of quality control procedures for home point-of-care (POC) international normalized ratio (INR) devices is a concern. Concomitant laboratory and POC INR testing may be proposed to overcome the lack of quality control. However, a difference between the POC INR and the laboratory INR is not necessarily due to failure of the POC device. This study aimed to identify variables associated with a significant deviation between the POC INR and the laboratory INR. Children included in this retrospective cohort study performed at least one concomitant laboratory and POC INRs. Clinical and laboratory variables were assessed for an association with significant deviation within pairs of INR. A significant deviation was noted for 30 (15.3%) of the 196 pairs of INR measurements from 124 children. Relative to patients without deviations, patients with deviations were younger (odds ratio =0.91; P=.020), less experienced in the use of POC INR devices (odds ratio =0.89; P=.098), and more likely to have received an INR result from a laboratory using animal thromboplastin (odds ratio =2.81 vs. 0.37 for laboratories using human thromboplastin; P=.016). In a multivariate analysis, younger age and the laboratory's use of animal thromboplastin were associated with significant deviations. Although most children had coherent pairs of INR values, the occurrence of deviations raises the question of the origin of the thromboplastin used in the laboratory and emphasizes the need to provide specific quality control procedures for POC INR devices.

Comparison of Sampling Methods for International Normalized Ratio Monitoring in Haemodialysis Patients (INRHaemo Study)

Background: Haemorrhagic and thrombotic complications are common in dialysis patients on warfarin; thus, accurate international normalized ratio (INR) monitoring is critical. For expediency and patient comfort, blood sampling from the haemodialysis access or circuit is commonly performed. Point-of-care (POC) INR machines allow both peripheral vein preservation and rapid results, yet are not validated in the haemodialysis population. Methods: A prospective cohort study in haemodialysis patients taking warfarin was undertaken. Three paired samples were drawn over a single session: peripheral blood INR, POC INR, and dialysis INR. Agreement using Bland-Altman analysis and correlation coefficients between the peripheral blood INR, haemodialysis INR, and POC INR were calculated. Inappropriate dosing decisions based on haemodialysis or POC INR were quantified. Results: Amongst 34 patients, agreement between the dialysis INR and peripheral blood INR was high, with the haemodialysis INR differing from the peripheral INR by <±0.2, 85.2% of the time. Correlation between the 2 methods was high (r = 0.914; p < 0.001). POC INR differed from peripheral INR values by <±0.2, 67.6% of the time, with less agreement at higher INR values. Dosing decisions were incongruent between the dialysis and peripheral INR in 6%, whilst the POC and peripheral INR disagreed in 26%. Conclusions: There was good agreement and correlation between the peripheral blood, haemodialysis access/circuit, and POC INR values. POC INR was less reliable at higher values, and dosing decisions differed from the peripheral INR in a quarter of cases.

Drive Through Point of Care International Normalized Ratio Testing During the COVID-19 Pandemic

In order to help combat COVID-19 and provide consistent and safe care for the veterans at the West Palm Beach Veterans Affairs Medical Center (WPVAMC), a drive through Point of Care International Normalized Ratio (POC-INR) testing site was implemented. This drive through clinic allows veterans taking warfarin to safely obtain anticoagulation management while complying with social distancing guidelines.

Comparison of prothrombin time and international normalized ratio values using point-of-care system with a standardized laboratory method in patients on long-term oral anticoagulation – A prospective study

Background: In our country, methods of prothrombin time (PT) and international normalized ratio (INR) testing have not been standardized across various centers. Often, we find disparity in INR values from different laboratories, posing a challenge to make an appropriate clinical decision. Objective: The objective of the study was to compare and correlate the PT/INR values using a point-of-care (POC) system with standardized laboratory (SL) testing and to evaluate the efficiency of the POC system in monitoring patients. Methods: We have prospectively compared PT/INR values between a commercially available POC, CoaguChek XS System, Roche, and SL testing in 205 patients and 353 samples from July 2017 to April 2018. Results: The overall strong correlation between POC PT/INR values and simultaneous standard laboratory values was noted. The overall coefficient of correlation among the two groups was 0.919 (P = 0.001) for INR values. In INR range of 2–3.5, the values correlated well with a coefficient of correlation, 0.756 (P = 0.001). In INR range 4. Conclusions: In this comparison study, statistical analysis yielded a good correlation between POC PT/INR values and SL values in therapeutic and subtherapeutic range. POC testing is a good alternative to SL testing. If widely available, POC testing may enable patient self-testing and self-monitoring. In our experience, POC testing had added benefits in emergency settings. However, clinicians and laboratory professionals should be aware of the occasional disagreement between POC INR and standard laboratory INR values.

Use of a capillary specimen in the laboratory to verify a point-of-care international normalized ratio: Avoidance of a venipuncture in a pediatric setting.

Point-of-care (POC) international normalized ratio (INR) values above an institutional cutoff are confirmed in the laboratory using a gold standard venous specimen. This can be problematic in a pediatric setting. In this study, 449 consecutive POC INR results were compared to an INR performed in the laboratory on a capillary citrate specimen collected from the same finger-stick. The results were statistically analyzed. The mean INR values from the CoaguChek XS and laboratory were 2.85±1.19 and 2.63±1.11, respectively. There was a good correlation between the methods with r=0.97. Bland-Altman analysis indicated a bias of 0.22 favoring the CoaguChek XS, with 95% limits of agreement -0.29 to 0.72. Passing and Bablok method comparison resulted in a slope of 0.91 (y=0.91x+0.02). An INR of ≤0.5 was found between the methods in 89% of cases and 84% agreement was noted (κ=0.69). Comparing the capillary INR laboratory results to studies involving a venous specimen, the capillary specimen performed with equivalence. Thus, a capillary citrate specimen can be collected from the same finger-stick used to perform the POC INR for confirmation in the laboratory. This avoids the trauma of a venous collection in such a situation.

Comparison of two point-of-care international normalized ratio devices and laboratory method.

: A number of factors contribute to interlaboratory variation of international normalized ratio (INR) results. This variability can lead to differences in clinical decision-making. This prospective cohort study evaluated the accuracy, precision, and clinical decision-making variability of two point-of-care (POC) devices (CoaguChek XS and the Coag-Sense) to a clinical laboratory method of INR measurement as the 'reference' and by using the laboratory's accuracy standard (±25% of the reference INR). Study subjects included adults taking warfarin undergoing a POC INR with each device and a laboratory INR on the same day and evaluated differences in clinical decision-making using a warfarin nomogram. A correction factor was derived for each POC method to estimate the corresponding laboratory INR for POC INRs more than 3.0. A total of 100 patient encounters (76 unique patients) included INR testing by all three methods. Both POC devices demonstrated excellent precision across the entire range (r = 0.98), but poor accuracy relative to the laboratory standard for POC INRs greater than 3.0 (accuracy CoaguChek 19% and Coag-Sense 35%). A correction factor applied to POC INRs greater than 3.0 improved accuracy to 99% for both devices. Applying the correction factor also significantly reduced differences in clinical decision-making (49-28% for CoaguChek and 56-40% for Coag-Sense, P < 0.001). Both POC devices demonstrated poor accuracy for INRs over 3.0. A device-specific, institution-specific correction factor applied to POC INRs greater than 3.0 can provide better accuracy of INR measurement and can significantly reduce variability in warfarin dosing decisions. More study is needed to assess impact on clinical adverse events.

Correction factor to improve agreement between point-of-care and laboratory International Normalized Ratio values

Results of a research project to quantify and improve the accuracy of point-of-care (POC) International Normalized Ratio (INR) values are reported. The accuracy of POC INR values relative to laboratory-measured INR values was retrospectively assessed in a cohort of patients with same-day INR determinations by both methods. Univariate linear regression was performed to derive a correction factor for POC INR values of >3; this correction factor was validated in a second cohort. In the derivation cohort (259 patients and 344 paired INR results), agreement of POC values with corresponding laboratory INR values at two specified thresholds (±15% and ±25%) was 51.2% and 66.6%, respectively; for POC INR values of >3 (n = 205), agreement was lower (24.9% and 44.9%, respectively). Univariate linear regression yielded a coefficient of 0.77 (95% confidence interval, 0.76-0.79; p < 0.001). Applying a correction factor of 0.8 to POC INR values in a validation cohort (169 patients and 209 paired INR values) significantly improved the accuracy of POC INR values of >3 relative to laboratory values (from 7% to 71.1% at the lower threshold and from 23.5% to 88.8% at the higher threshold, p < 0.0001 for both comparisons). Agreement between POC and laboratory INR results in one institution was poor, especially when POC INR values exceeded 3. Application of an institution-specific correction factor to POC INR values of >3 improved agreement with laboratory INR results but would not have significantly reduced differences in protocol-based warfarin dosage adjustments.

Impact of point‐of‐care international normalized ratio monitoring on quality of treatment with vitamin K antagonists in non‐self‐monitoring patients: a cohort study

Point-of-care (POC) international normalized ratio (INR) monitoring by healthcare professionals could eliminate the need for venous blood sampling in non-self-monitoring (NSM) patients on vitamin K antagonists (VKA). However, few studies have investigated the impact of POC INR monitoring on the quality of treatment in these patients and real-world data on this issue are lacking. To investigate the safety, efficacy and quality of anticoagulant control during POC INR monitoring as compared with laboratory INR monitoring in NSM patients. We performed a retrospective cohort study using data from the anticoagulation clinic of the Star-Medical Diagnostic Center (Rotterdam, the Netherlands). Patients who received treatment with VKA between 29 May 2012 and 29 May 2014 were eligible. Percentage of time in therapeutic range (TTR) and incidence rates of major clinical events (all-cause mortality, hospitalization, major bleeding and ischemic stroke) were compared for the year before and year after introduction of POC monitoring. Cox proportional hazard models were used to estimate hazard ratios and 95% confidence intervals for major clinical events between exposure groups. In total, 1973 patients during the 1-year laboratory-monitoring observation period and 1959 patients during the 1-year POC-monitoring observation period were included. Median TTR was significantly lower during POC monitoring (77.9%; 95% CI, 67.2-87.4) than during laboratory INR monitoring (81.0%; 95% CI, 71.1-90.5). Adjusted hazard ratios for major clinical events were all around unity. Although associated with lower TTR, POC INR monitoring is a safe and effective alternative to laboratory INR monitoring in NSM patients on VKA.

Point-of-care international normalized ratio testing is rapid and reliable: A prospective observational cohort study

Background: International normalized ratio (INR) >1.5 may indicate need for reversal of coagulopathy or massive transfusion (MT) in trauma patients. Thus, obtaining INR values as early as possible would expedite both clinical decisions. This study evaluates the reliability of using a point-of-care (POC) device to obtain INR results more rapidly. Methods: A trained pharmacist used the CoaguChek® XS Plus (Roche Diagnostics, Basel, Switzerland) device to determine POC INRs in venous blood from adult (>18 years) trauma patients not transfused prior to arrival. POC and laboratory INR (lab INR) values and times to availability were compared. The POC INR value was not used for clinical treatment decisions. Results: POC INR was performed on 177 patients; 43 were excluded due to missing lab INR or later recognition of prehospital blood transfusion. The mean lab INR was 1.163, and the mean POC INR was 1.167. The paired samples correlation was 0.958 (P Conclusion: This study confirms that POC INR is a rapid, reliable tool to detect patients who may need prompt reversal of anticoagulant medications or initiation of MT. The following core competencies are addressed in this article: Patient care, Medical knowledge, Systems based practice

Point of care coagulometry in prehospital emergency care: an observational study.

BackgroundHaemostatic impairment can have a crucial impact on the outcome of emergency patients, especially in cases of concomitant antithrombotic drug treatment. In this prospective observational study we used a point of care (POC) coagulometer in a prehospital physician-based emergency medical system in order to test its validity and potential value in the treatment of emergency patients.MethodsDuring a study period of 12 months, patients could be included if venous access was mandatory for further treatment. The POC device CoaguChek® was used to assess international normalized ratio (INR) after ambulance arrival at the scene. Results were compared with in-hospital central laboratory assessment of INR. The gain of time was analysed as well as the potential value of POC testing through a questionnaire completed by the responsible prehospital emergency physician.ResultsA total of 103 patients were included in this study. POC INR results were highly correlated with results of conventional assessment of INR (Bland-Altman-bias: 0.014). Using a cutoff value of INR >1.3, the device’s sensitivity to detect coagulopathy was 100 % with a specificity of 98.7 %. The median gain of time was 69 min. Treating emergency physicians considered the value of prehospital POC INR testing ‘high’ in 9 % and ‘medium’ in 21 % of all patients. In patients with tracer diagnosis ‘neurology’, the value of prehospital INR assessment was considered ‘high’ or ‘medium’ (63 %) significantly more often than in patients with non-neurological tracer diagnoses (24 %).ConclusionsAssessment of INR through a POC coagulometer is feasible in prehospital emergency care and provides valuable information on haemostatic parameters in patients. Questionnaire results suggest that POC INR testing may present a valuable technique in selected patients. Whether this information translates into an improved management of respective patients has to be evaluated in further studies.

Bridging the gap between point-of-care testing and laboratory testing in hemostasis.

Point-of-care (POC) testing within hemostasis is an expanding field, with the most widely used test being POC international normalized ratio (INR). Many of these devices are being used in a nonlaboratory setting by staff with no laboratory training. In the United Kingdom, external quality assessment (EQA) is provided by the organization UK National External Quality Assessment Scheme for Blood Coagulation (UK NEQAS BC). Participants within the UK NEQAS BC POC INR program are largely based in primary care (77%), with the majority of EQA samples and patients tests being performed by nurses (70%). Many of these centers do not have support from the laboratory staff and may, therefore, not understand the requirement for a robust quality control (QC) system comprising both internal quality control (IQC) and EQA. From data acquired through a questionnaire of these UK NEQAS BC users, we observed that 2% of the centers never perform IQC tests, only 29% perform IQC tests when starting a new batch of test strips, and just 15% carry out IQC with each clinic as recommended by the UK guidelines. The imprecision of EQA tests was greater for POC users than in the UK NEQAS BC hospital laboratory program, with average coefficients of variation for a 2-year period of 11.0 and 7.3%, respectively. This may reflect the handling of EQA samples rather than the imprecision of the method, due to the lack of laboratory training amongst POC staff. POC INR in the UK could greatly benefit from more interaction and support from laboratories to these POC testers.

Near-patient testing devices to monitor vitamin K antagonists

Monitoring of the anticoagulant effect with the International normalized ratio (INR) is essential for patients receiving vitamin K antagonists (VKAs). The majority of point of care (POC) devices for INR monitoring has shown a good precision and accuracy with results similar to those obtained in a laboratory. In many countries, INR POC devices are widely used at home by the patients for self-testing. Their use in the hospital by the clinical staff (doctor or nurses) for bedside measurement is also growing. The INR POC testing is performed using fully automated devices. Capillary blood samples are easy to obtain. In the emergency room, POC INR devices are commonly used. This improves the quality of care for patient with suspicion of VKAs overdosage. INR measurement using bedside monitors is also of great interest in care units for specific populations of patients like paediatrics or geriatrics. Moreover, bedside INR monitoring may be useful in anticoagulant clinics or when the care unit is far from a laboratory. Although the bedside INR monitors are easy to use, their implementation requires adequate training and intermittent re-evaluation of any person performing the tests to ensure reliability of results. Such equipment must comply with EN ISO 22870 standard for POC testing accreditation, under the supervision of a biologist. In order to achieve these targets, connect the instrument to the laboratory's data management system is essential.

An analysis of discrepancy between point-of-care and central laboratory international normalized ratio testing in ED patients with cerebrovascular disease

ObjectiveOur objective was to identify demographic, clinical, and operational variables associated with discrepancy between point-of-care (POC) and central laboratory international normalized ratio (INR) results in emergency department (ED) patients with acute cerebrovascular disease. MethodsWe conducted a retrospective, observational cohort study of a series of 637 patients with acute cerebrovascular disease over 30 months who underwent simultaneous POC, using the i-STAT POC analyzer (Abbott, Princeton, NJ), and central laboratory INR testing at ED presentation. Point-of-care INR results greater than ±0.25 INR units from the central laboratory INR value were considered discrepant. We analyzed potential predictors of POC INR discrepancy from demographic, clinical, and operational variables using multivariable logistic regression. We evaluated the change in POC INR discrepancy incidence over the study interval using analysis of variance methodology. ResultsThe final diagnoses of the 637 subjects were acute ischemic stroke (n=427), transient ischemic attack (n=105), and intracranial hemorrhage (n=105). Discrepant POC INR results occurred in 21.5% (137/637) of subjects. The mean bias between POC and central laboratory INR was 0.24 ± 0.69 (range, 0-11.3). Significant covariates of POC INR discrepancy were oral anticoagulant use (odds ratio, 3.03; confidence interval, 1.37-6.68) and increasing activated partial thromboplastin time (aPTT) (odds ratio, 1.07; confidence interval, 1.02-1.12). We observed a significant reduction trend in the incidence of POC-central laboratory discrepancy over the study period, decreasing on average at 0.42% per month (F=5.59, P=.025). ConclusionIn this retrospective study, oral anticoagulant use and increasing aPTT were significantly associated with POC INR discrepancy in ED patients with acute cerebrovascular disease. Point-of-care INR discrepancy incidence decreased over the study interval.

Novel analysis of clinically relevant diagnostic errors in point‐of‐care devices

To ensure proper clinical decision-making and avoid preventable harm, the quality of point-of-care (POC) device measures is routinely assessed. Traditional analyses may not reveal clinically important diagnostic errors. To compare results between a novel analytic framework and traditional analyses. Patients in four anticoagulation clinics provided two measures of the International Normalized Ratio (INR) at the same visit as part of routine quality assurance: one via a venous sample and one fingerstick. These were assessed with Hemochron POC devices. Traditional, quarterly, quality assurance assessments emphasized correlation analysis. The novel analysis used enhanced graphics and a validated assessment of clinical decision-making. 1518 paired INRs were analyzed. The correlation between the POC and laboratory assessments ranged between 0.84 and 0.91. Traditional quality assurance showed that the Hemochron devices were acceptable for continued use in each quarterly analysis. Enhanced graphical analysis demonstrated that the Hemochron devices never reported seven common INR values. The Hemochron devices systematically inflated values < 3 and deflated values > 4, biasing results towards the target INR range. Consequently, the Hemochron devices lead to a different clinical decision than the clinical laboratory measure in 31% of cases (458/1466; 95% confidence interval [CI] 29-34). When the reference INR was low, the Hemochron devices would not result in appropriate dose increases in 52% of cases (95% CI 48-56), placing these patients at risk for a significant adverse drug event. Our novel, clinically relevant analysis revealed previously undetected deficiencies in our POC INR devices, and our approach should be adopted by industry, regulators, and institutions.

Accuracy of a portable international normalized ratio monitor for patients receiving a low molecular weight heparin as a bridge pending full oral anticoagulant efficacy

Background Point of care (POC) devices measuring the international normalized ratio (INR) are accurate for patients with stable disease, but their efficiency has not been prospectively assessed during the “bridging period” when patients are receiving a low molecular weight heparin (LMWH) on top of a vitamin K antagonist (VKA) until the target INR is reached. Methods 188 dual INR measurement using the POC (INR POC) and the laboratory (INR lab) at the same time were consecutively determined : 69 in patients receiving LMWH + VKA (bridging group) and 119 in patients receiving only a VKA (control group). INRpoc was compared to INR lab. Results Test strip failure rate was higher in the bridging group than in the control group (29% vs 4% ; p < 0,001). In successful tests, POC accuracy was not modified by LMWH administration: the correlation coefficients between POC and lab INR values for the bridging group and the control group were 0,81 and 0,87 respectively, and the relative measure of divergence (RMD = INR lab – INR poc / INR lab) was lower in the bridging group than in the control group (4 ± 7% vs 10 ± 14%; p = 0,02). Finally, clinically relevant agreement between POC and laboratory was of 90% in the bridging group and 92.1% in the control group (p = 0.6). Conclusion With the POC used (INRatio), in patients receiving LMWH when the POC gives a result, it is as accurate as in patients not receiving a LMWH.

Point-of-Care International Normalized Ratio Testing Accelerates Thrombolysis in Patients With Acute Ischemic Stroke Using Oral Anticoagulants

Thrombolysis in patients using oral anticoagulants (OAC) and in patients for whom information on OAC status is not available is frequently delayed because the standard coagulation analysis procedure in central laboratories (CL) is time-consuming. By using point-of-care (POC) coagumeters, international normalized ratio (INR) values can be measured immediately at the bedside. The accuracy and effectiveness of POC devices for emergency management in acute ischemic stroke has not been tested. In phase 1, the reliability of emergency INR POC measurements in comparison to CL was determined. In phase 2, patients with ischemic stroke admitted within the time frame for systemic thrombolysis and who were either using OAC or for whom information on OAC status was not available were enrolled. Patients received thrombolysis if POC INR was <or=1.5. Precision and time gain was recorded for INR as measured by POC vs CL. In phase 1 (n=113), Bland-Altman analysis showed close agreement between POC and CL, and Pearson correlation was highly significant (r=0.98; P<0.01). In phase 2, 48 patients were included, of whom 70.8% were using OAC; 23 patients received thrombolysis. After subtracting the time needed for the diagnostic work-up, the net time gain was 28+/-12 minutes (mean+/-SD). Measuring INR by POC in an emergency setting is sufficiently precise in OAC acute stroke patients and substantially reduces the time interval until INR values are available and therefore may hasten the initiation of thrombolysis.

Correlation of Point-of-Care International Normalized Ratio to Laboratory International Normalized Ratio in Hemodialysis Patients Taking Warfarin

To determine whether point-of-care (POC) International Normalized Ratio (INR) test results correlate with plasma INR measures in intermittent hemodialysis (IHD) patients on warfarin. Anemia is thought to reduce the accuracy of POC INR assay results. Whether POC INR testing could be implemented for hemodialysis patients on chronic warfarin, who are often anemic despite hematopoietic therapy, has not been established. Thirty-seven chronic hemodialysis patients on warfarin contributed sets of three consecutive blood samples for INR comparison immediately before hemodialysis: one finger stick, two from hemodialysis access (arteriovenous graft, fistula, or catheter). POC INR testing was performed using CoaguChek S device. Anemia was defined as hematocrit < 32%. Pairwise comparison and correlation of 258 INR results showed high correlation for POC versus laboratory INR (r = 0.94; P < 0.001). Of these, 16 (6%) differed by >0.6 INR units, four (1.6%) differed by >0.8 INR units, and one differed by >1.0 INR units. Resulting pairwise correlation analyses between samples were: for anemic patients (0.96; P < 0.001), nonanemic patients (0.93; P < 0.001), and for those obtained from arteriovenous grafts (0.94; P < 0.001). POC INR samples from dialysis catheters correlated poorly with laboratory INR results. POC INR correlates well with plasma INR measures in IHD patients requiring chronic warfarin, and anemia did not influence this reliability. Blood sampling from finger stick or arteriovenous graft or fistula showed excellent correlation with laboratory INR, whereas sampling from dialysis catheters was unsatisfactory, likely from heparin contamination.

Point-of-Care INR Measurement in Children Requiring Warfarin: What has been Evaluated and Future Directions

Many children are surviving primary illnesses and now require thromboprophylaxis as a result of advances in management. Vitamin K antagonists are commonly prescribed to prevent or treat thrombosis. These agents are far more challenging to effectively manage in children. As a result of these challenges, frequent blood monitoring to measure international normalized ratio (INR) values is required. Point-of-care (POC) INR monitors use a capillary blood sample that has been expressed as a solution to improve effective management of vitamin K antagonist therapy. POC INR meters have been demonstrated to be accurate and precise in measuring INRs. Implementation of a standardized education program prior to patient use of POC meters results in differences between measured laboratory INRs and POC INR comparisons that meet criteria for clinical relevance. This indicates that POC INR meters are safe and effective for use in children.