Laboratory 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.

The Concordance between Laboratory and POCT INR and the Value of Bedside Measurement of INR in Patients on Warfarin Undergoing Dental Procedures: A Prospective Cohort Study

Introduction: Patients on anticoagulation particularly warfarin suffers when they have a dental problem that requires intervention. Most of dentists worry and refuse to perform procedures on patients on warfarin because of the risk of bleeding and request the availability of international normalized ratio (INR) results before procedure which can delay the procedure and add another burden on the patient particularly who live away from the treating center. Objective: To evaluate the efficacy and the value of using point of care testing (POCT) (INR) in patients on warfarin undergoing dental procedures. We also had analyzed the frequency and severity of dental bleeding in patients on warfarin therapy and the concordance between Laboratory based INR and POCT INR. This is the first interim analysis on ongoing prospective study. Methods: A cohort study of 30 patients on chronic use of anticoagulation therapy with warfarin for different clinical indications who planned to undergo dental procedures at a teaching hospital in Saudi Arabia. The patients' demographic and clinical characteristics, type and severity of bleeding, and INR measured by both HemoChrone (POCT) and prothrombin time (PT) were performed at same time. Descriptive statistics, paired samples statistics, correlations, and analysis of variance (ANOVA) were performed. Results: The sample consisted of 60% females, with a mean age of 49.9 (SD 13.3) years. The most common indications for warfarin therapy were mechanical aortic valve replacement (56.7%), atrial fibrillation (13.3%), and atrial flutter (16.7%). Before the procedure, the mean Laboratory INR was 2.6 (SD 0.6) and the mean HemoChrone POCT INR was 2.8 (SD 0.8). There was a significant positive correlation between the two methods (r = 0.81, p &amp;lt; 0.001). There was no significant difference in the INR and type of bleeding, dentist performed the procedure, or dose of warfarin. There was no correlation between the Bleeding severity or type and the INR level in patients undergoing different dental procedures. Even among those with HemoChrone POCT INR &amp;gt; 3, which is considered high and increases the risk of bleeding, there was no significant correlation with bleeding. Conclusion: These results imply that warfarin therapy can be safely continued for most dental procedures without increasing the risk of bleeding regardless of the INR results. The HemoChrone POCT INR is a dependable and practical method to monitor the effect of warfarin in dental settings which can reassure the dentists before procedure. Figure 1: The concordance between Laboratory and POCT INR

Accuracy and Precision of Point-of-Care International Normalized Ratio in Patients With Liver Disease.

To determine if the CoaguChek XS Pro Point-of-Care (POC) device can accurately and precisely measure the international normalized ratio (INR) compared with the gold standard laboratory INR in pediatric and adult patients with liver disease. This prospective cohort study included 15 pediatric patients without liver disease, 13 pediatric patients with liver disease, and 17 adult patients with liver disease. The accuracy of the POC INR values was determined using the correlation and Bland-Altman limits of agreement. The accuracy of the coagulometer INR was assessed by calculating the proportion of POC INR measurements that were ≤15% of their corresponding laboratory INR. A comparison of INR measurements showed an excellent correlation in pediatric patients without liver disease ( r = 0.82), pediatric patients with liver disease ( r = 0.89), and adult patients with liver disease ( r = 0.96). Fourteen (93%) POC INR values were ≤15% in pediatric patients without liver disease from its paired laboratory INR. All 13 paired measurements were ≤15% in pediatric patients with liver disease. In adult patients with liver disease, 12 (71%) POC INR values were ≤15% of their paired laboratory INR. In patients with liver disease, the CoaguChek XS Pro provides an accurate measure of the INR compared to laboratory INR measurements.

CoaguChek® XS versus standard laboratory prothrombin time for anticoagulant monitoring in patients with antiphospholipid syndrome.

The standard of care for thrombotic antiphospholipid syndrome (APS) is anticoagulation with vitamin K antagonists (VKAs). Prothrombin time, and its corresponding international normalized ratio (INR), is the laboratory test routinely performed to assess anticoagulation. Self-management of VKA therapy using point-of-care (POC) devices seems to be an attractive option. To evaluate the accuracy of a POC device (CoaguChek XS) in APS patients by comparing it with venous laboratory INR. Furthermore, we analyzed whether other clinical and laboratory features could interfere with the CoaguChek XS results. This is a single-center cross-sectional study with 94 APS patients from a tertiary rheumatology clinic performed from August 2014 to March 2015. The comparison between CoaguChek XS and venous laboratory INR results was evaluated using the coefficient of determination (r) followed by the Bland-Altman test. A paired t-test was also applied. A difference of up to ±0.5 INR unit between the two systems was considered clinically acceptable. The mean CoaguChek-INR was 2.94 ± 1.41 and venous laboratory INR was 2.43±0.86, with a correlation coefficient (r) of 0.95. Categorizing INR values in ranges (INR <2, INR 2-3, INR 3-4, and INR >4), we found that the INR >4 group presented a lower correlation (r = 0.64) compared to the other ranges (p < 0.05). Although both methods were highly correlated, CoaguChek XS showed higher values than the venous laboratory INR, with an increased average of 0.42 ± 0.54. Therefore, we proposed a simple linear regression model to predict the venous laboratory INR values, using results obtained from CoaguChek XS. A difference ≤0.5 INR unit between the two systems was observed in 57.4% of patients, and the aPL profile did not influence the results. Although CoaguChek XS and venous laboratory INR demonstrated a good linear correlation in the group of INR ≤4, extra caution should be taken in APS patients, since a reasonable proportion of patients can present differences in INR results that are not acceptable. We do not recommend routine POC in APS patients.

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.

Evaluation of point‐of‐care International Normalized Ratio in sickle cell disease

BackgroundPoint‐of‐care (POC) International Normalized Ratio (INR) measurement provides efficient monitoring of warfarin therapy; however, its reliability may be affected in patients with anemia, such as those with sickle cell disease (SCD). ObjectivesTo evaluate the correlation of POC‐INR to clinical laboratory INR (CL‐INR) in SCD and use of a correction factor. Patient/MethodsIn this retrospective study, the accuracy of POC‐INR compared to CL‐INR was evaluated in a cohort of patients with SCD and in a non‐SCD Black cohort. ResultsDespite the difference in anemia, the SCD cohort showed a similar percentage of in‐range POC‐INR values as observed in the non‐SCD cohort (37% vs 42%). The SCD cohort was randomly divided to form discovery and validation cohorts. In the discovery cohort, 86% of POC‐INRs were in range when the POC‐INRs were ˂4.0, but only 24% were in range if POC‐INRs were ≥4.0. A linear regression of CL‐INR versus POC‐INR for POC‐INR values ≥4.0 yielded a coefficient of 0.72 (95% confidence interval, 0.69‐0.75); Multiplying POC‐INR by this correction factor, rounded to 0.7 for ease of use in clinical practice, improved the proportion of in‐range POC‐INR values ≥4.0 from 24% to 100% in the SCD discovery cohort and from 19% to 95% in the SCD validation cohort. Similar findings applied to analyses of the non‐SCD cohort. ConclusionsPOC‐INR and CL‐INR in patients with SCD are similar when POC‐INR is <4.0, and the accuracy of POC‐INR values ≥4.0 can be improved by applying an institution‐specific correction factor.

Correction of Point-of-Care International Normalized Ratio (INR) Values in Patients with Sickle Cell Disease

Background: With a narrow therapeutic range, warfarin use needs to be closely monitored to minimize the risk of bleeding or thrombosis. Point-of-care (POC) International Normalized Ratio (INR) tests using finger stick blood samples provide instantaneous results and improve testing efficiency; however, the test accuracy of POC-INR may be affected by various factors such as anemia (1, 2). Thrombosis and warfarin use are prevalent in patients with sickle cell disease (SCD) (3), but evidence on the accuracy or correction of POC-INR in this patient population is lacking. This study evaluates correlation of POC-INR to clinical laboratory INR (CL-INR) in patients with SCD. Methods: POC-INR and CL-INR values measured within 12 hours of each other in patients with SCD treated at the UI-Health from 2015-2017 were collected. A total of 28 INR pairs were used to form a discovery cohort. A cohort of non-SCD African American (AA) patients with POC-INR and CL-INR values measured within 12 hours who were treated at UIC-Health during the same period were utilized as a control group. Patient demographic and clinical characteristics were recorded to calculate a correction factor. Additional 28 POC- and CL-INR pairs in patients with SCD were used to form a validation cohort. Descriptive statistics, Kruskal-Wallis test, Chi-square test, and linear regression were used for data analysis. The study was approved by the UIC Institutional Review Board (protocol #2020-0191). Results: In the discovery cohort with 100% AA patients, POC-INR in an acceptable range of the CL-INR, defined as an INR difference within ±0.5 INR of CL-INR when POC-INR &amp;lt; 2 or ±30% of CL-INR when POC-INR ≥ 2 (4), was present in 6 of 7 (86%) of patients when INR &amp;lt; 4 compared to 5 of 21 (24%) when INR ≥ 4. For POC-INR ≥ 4, a correction factor of 0.7 was derived using a linear regression model (95%CI: 0.685-0.752, P&amp;lt;0.001, R square: 0.991), which significantly improved the in-range POC-INR from 24% to 100% in the discovery cohort (P&amp;lt;0.001). In the validation cohort, the in-range POC-INR increased from 19% to 95% (P&amp;lt;0.001) after applying the correction factor of 0.7 (Figure 1). When compared to the non-SCD AA cohort, the patients with SCD were younger (38 vs 59 years, P&amp;lt;0.001) and more anemic (HCT 27% vs 37%, P&amp;lt;0.001). However, there was no significant difference in the in-range POC-INR percentage (37% vs 42%, P = 0.547) (Table 1). The correction factor for POC-INR ≥ 4 in the non-SCD AA cohort was the same as the SCD cohort as 0.7. Summary: POC-INR over-estimates a simultaneous CL-INR when POC-INR ≥ 4 in patients with SCD, and a correction factor significantly improved the agreement with CL-INR. Despite the difference in anemia, the accuracy of POC-INR and correction factor were similar between SCD patients and non-SCD AA patients. An institution-specific correction factor for POC-INR ≥ 4 should be applied similarly to both SCD and non-SCD patients. Reference: 1. R. W. Hoel et al., Correlation of point-of-care International Normalized Ratio to laboratory International Normalized Ratio in hemodialysis patients taking warfarin. Clin J Am Soc Nephrol4, 99-104 (2009). 2. C. E. DeRemer, B. McMichael, H. N. Young, Warfarin Patients With Anemia Show Trend of Out-of-Range International Normalized Ratio Frequency With Point-of-Care Testing in an Anticoagulation Clinic. J Pharm Pract32, 499-502 (2019) 3. A. Srisuwananukorn et al., Clinical, laboratory, and genetic risk factors for thrombosis in sickle cell disease. Blood Adv4, 1978-1986 (2020). 4. W. Plesch et al., Results of the performance verification of the CoaguChek XS system. Thromb Res123, 381-389 (2008). Disclosures Gordeuk: CSL Behring: Consultancy, Research Funding; Global Blood Therapeutics: Consultancy, Research Funding; Imara: Research Funding; Ironwood: Research Funding; Novartis: Consultancy. Saraf:Novartis, Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Boards, Speakers Bureau; Pfizer, Global Blood Therapeutics, Novartis: Research Funding.

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.

How to Generate a More Accurate Laboratory-Based International Normalized Ratio: Solutions to Obtaining or Verifying the Mean Normal Prothrombin Time and International Sensitivity Index.

Although the landscape of anticoagulation therapy is evolving, vitamin K antagonists (VKAs) such as warfarin remain an anticoagulant of choice for many clinicians and their patients. Nevertheless, management of VKA therapy remains challenging, largely because of patient variability and drug and food interactions; thus, VKA dosing has to be personalized. This is achieved by regular monitoring using a test called the prothrombin time (PT), mathematically converted to an international normalized ratio (INR). The INR system is meant to harmonize laboratory test results by taking into account reagent and instrumentation variability that is otherwise expected to give rise to variable PT values, but which should accordingly lead to less variable INR values. Of clinical importance, too low an INR is suggestive of increased thrombotic risk and typically means the VKA dose should be increased, whereas too high an INR is suggestive of increased bleeding risk and typically means the VKA dose should be temporarily withheld and/or decreased. However, evidence continues to show that variability in INR values between laboratories remains unacceptably high. Given that modern instrumentation provides for robust analytical values-meaning highly reproducible intralaboratory clotting times or PTs in this case-the most likely cause of high INR variability is inconsistency in the INR test components-meaning the MNPT (mean normal PT) and ISI (international sensitivity index) values used by laboratories to generate a given INR. In other words, there are doubts as to the accuracy of some INR values because there are corresponding doubts about the accuracy of MNPT and/or ISI values that have been assigned by some laboratories for their reagent/instrument combination. The current report is intended to provide some solutions around the problems of inaccurate INRs, ISIs, and MNPTs, thus aiming to drive laboratory INRs closer to "truth," and thus promote better patient management. The novel strategies include a primary process of transference to obtain/verify MNPT and/or ISI values for a new reagent using an existing reagent as reference, and a secondary process whereby external quality assessment data can be used to correct bias or existing errors in assigned MNPT and/or ISI values.

Verification of the qLabs international normalized ratio point-of-care device for monitoring of patients attending an anticoagulation clinic.

In the developing world, point-of-care (POC) testing for international normalized ratio (INR) plays an important role in the monitoring of patients on long-term warfarin therapy with limited access to healthcare ensuring safe and effective anticoagulation. A newly developed POC device for INR measurement by healthcare workers is the handheld qLabs POC device® (Micropoint Biotechnologies Incorporated, Guangdong, China). The qLabs POC device® was evaluated in 262 patients attending an anticoagulation clinic with regards to accuracy and precision of the INR results. The results were compared to the results obtained on the Stago STA R Max® coagulation analyzer (Stago Diagnostica, Paris, France) on a wide range of normal and abnormal results of clinical relevance. The mean laboratory INR (2.50±1.08) was significantly higher than the qLabs POC device® INR (2.38±1.07) (P<.0001). The correlation coefficient (r) was .88, the slope coefficient was 1.0 (CI, 0.8-1.2), and the intercept was -0.10 (CI, -0.50 to 0.30). The mean of the differences was -0.13% (CI, -0.19 to -0.06). Dosage concordance was 85.46% and clinical agreement was 92.37%. However, clinical agreement was 42.42% in the subgroup above the target range (>3.5). The imprecision was within acceptable limits (<5%) and the error message rate was 4.38%. In conclusion, the qLabs POC device® is accurate and precise with high levels of dosage concordance and clinical agreement for INR values within and below the target range.

Prospective Comparison of Point-of-Care Device and Standard Analyzer for Monitoring of International Normalized Ratio in Outpatient Oral Anticoagulant Clinic.

Point-of-care testing (POCT) coagulometers are increasingly being used in the hospital setting and patients’ self-testing. We determined the agreement of prothrombin time international normalized ratio (INR) results by POCT coagulometer and laboratory instrument through a comparative analysis and investigated whether the results of POCT coagulometer can reliably be used without being confirmed by standard laboratory analyzer. A total of 200 INR measurements by POCT coagulometer (CoaguChek XS Pro) and laboratory analyzer (Sysmex CS2000i) were compared using Passing-Bablok regression analysis and Bland-Altman plot. Agreement of the INR measurement was further analyzed in relation to dosing decision. The correlation of INR measurements between CoaguChek XS Pro and Sysmex CS2000i was excellent (correlation coefficient = 0.973). The overall mean difference was 0.21 INR ± 0.32 (range: 1.7-0.44). The mean difference was found to get increased as INR results increased and was 0.09 in the subtherapeutic range (≤1.9 INR), 0.29 INR in the therapeutic range (2.0-3.0 INR), while 0.4 INR in the supratherapeutic range (>3.0 INR). The overall agreement was excellent (κ = 0.916) and overall 11 (5.5%) of 200 INR measurements showed a difference in dosing decision between the 2 instruments. The positive bias of POC-INR is evident in the supratherapeutic range which could affect the dosing decision requiring confirmation with the laboratory INR measurement.

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.

Application of a Simulation Model to Estimate Treatment Error and Clinical Risk Derived from Point-of-Care International Normalized Ratio Device Analytic Performance.

In 2016, the Food and Drug Administration (FDA) proposed to enhance performance expectations for point-of-care testing (POCT) international normalized ratio (INR) devices relative to International Organization for Standardization (ISO) 17593:2007. The objective of the study was to estimate the frequency of warfarin dosing errors associated with a central laboratory INR method, a POCT INR method, and the proposed FDA performance goals. A data set of INR results (n = 51912) from adult patients with INR ≤4 was used to assess the influence of adding assay imprecision and bias on warfarin dose decisions. The frequency of error in warfarin dose and size of error (≥1 or ≥2 dose categories) was compared using published assay specifications for the Instrumentation Laboratory ACL TOP® and the Roche Diagnostics CoaguChek® XS relative to the proposed FDA guidelines. The frequency of warfarin dose misclassification was largely influenced by bias and was not sensitive to assay imprecision. The central laboratory and POCT INR methods met the FDA performance specifications, had equal rates of ≥2 warfarin dose category error, and had statistically different rates of ≥1 warfarin dose category error in large samples (n >250). Simulation models are useful tools for evaluating POCT INR assay performance criteria required to achieve the proposed FDA guidelines. This simulation depicted how the Roche Diagnostics CoaguChek XS instrument meets the guideline.

An evaluation of a coagulation system (Xprecia Stride) for utilisation in anticoagulation management

AimTo evaluate the reliability and performance of the Xprecia Stride coagulometer under the conditions in which it is most likely to be used.MethodsThe performance of the Xprecia Stride coagulometer was...

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.

227 - Home INR Monitoring Versus Lab Monitoring in Patients With Left Ventricular Assist Device

Introduction: Heart failure patients implanted with an axial or centrifugal left ventricular assist device (LVAD) are treated with warfarin to prevent pump thrombosis. Given the propensity for gastrointestinal bleeding with these patients, careful management of anticoagulation is an essential part of post-operative care. Given the intense involvement of these patients and care-givers, we hypothesized that home monitoring of international normalized ratio (INR) may be more effective than traditional laboratory testing. Methods: We performed a retrospective study of 42 LVAD patients for a six-month period at The Christ Hospital in Cincinnati, OH. INR targets were patient-specific based on clinical history. Twenty-six patients used home testing (HOME: Roche, Alere) with guidance from the LVAD team while 16 patients were monitored using laboratory INR testing (LAB). Monitoring choice was based on patient/physician preference and insurance coverage. Results: Home monitored patients were tested fewer times over the 6 month period than the laboratory group (27 versus 37). In the HOME group, 52% of the INR's were within target range and 48% were outside (26% above and 22% below target). In the LAB group, 36% of INR's were within range and 64% were outside (27% above and 37% below target). Accordingly, percentage of patients experiencing either a bleeding or thrombotic complication was less common in the HOME group compared to LAB (15% versus 25%). Number of thrombotic complications was similar between the two groups, but bleeding complications were less frequent in the HOME group (3 in 26 patients) vs. LAB (7 in 16 patients). Conclusions: LVAD Patients monitored for INR at home required fewer tests, were more likely to be in therapeutic range, and suffered fewer bleeding complications. Relatively low rate of in-target INR's are likely related to narrow ranges and multiple patient factors.

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

Correlation Between Home INR and Core Laboratory INR in Patients Supported with Continuous-Flow Left Ventricular Assist Devices.

It has been well established that patient self-testing (PST) of international normalized ratio (INR) using home monitoring devices increases the average therapeutic time and patient satisfaction. Long-term anticoagulation therapy with warfarin is used in patients with continuous-flow left ventricular assist device (CF-LVAD) to minimize the occurrence of thromboembolic events; however, PST devices have never been tested in patients with CF-LVADs. The purpose of this study was to determine the reliability of the PST device Alere INRatio 2 in patients supported with CF-LVADs. A correlation study was performed in 50 patients with CF-LVAD who were on stable warfarin therapy for a minimum of 3 weeks. Simultaneous INR values were determined from capillary whole blood samples using the Alere PST device and venous blood samples processed in the core laboratory at Columbia University Medical Center. There was a moderate correlation between the venous and the capillary INR values with a correlation coefficient of 0.83. The median difference between the methods was 0.39, with 44 of 50 patients recording higher INRs with Alere. Results remained unchanged after adjusting for use of amiodarone, abnormal hematocrit and liver enzymes, creatinine, and thyroid-stimulating hormone. Point of care testing with Alere correlates moderately well but consistently overestimates INR when compared with conventional laboratory testing in patients with CF-LVAD.