Performance of the microINR Point-of-Care System Used by Self-Testing Patients: A Multicenter Clinical Trial

Introduction Anticoagulation monitoring is a major practical and clinical challenge. We assessed the performance of the microINR system in patient self-testing (PST). Methods This study was performed at four US medical centers. After the training visit of warfarin anticoagulated patients (n = 117) on microINR system, PST was performed at home and in two visits to the medical centers. At the medical centers, both PST and healthcare professionals (HCPs) performed duplicate tests with the microINR System. A venous blood sample for the laboratory testing was also extracted. Accuracy and precision were assessed. Results The comparison between microINR PST results and microINR HCP results revealed an equivalence with a slope of 1.00 (95% confidence interval [CI]: 1.00–1.00), and an intercept of 0.00 (95% CI: 0.00–0.00). When compared with the laboratory analyzer, microINR PST results also showed good correlation with a slope of 0.94 (95% CI: 0.86–1.04) and an intercept of 0.14 (95% CI: -0.09–0.34). Predicted bias values at international normalized ratio (INR) 2.0, 3.5, and 4.5 were 0% against HCP and ≤2.5% against the laboratory. Analytical agreement with both HCP and laboratory was 100% according to ISO17593 and 99.1 and 100% according to CLSI POCT14 with HCP and laboratory, respectively. Clinical agreement with HCP regarding 2.0–4.0 as INR therapeutic range was 98% (within range). The precision (coefficient of variation) of microINR system used by PST was comparable to HCP. Conclusion The microINR results when used by self-testing patients show satisfactory concordance to both HCP results and laboratory analyzer. The microINR system is adequate for self-testing use.

Stability of Glucose Concentrations in Frozen Plasma

Background: Conflicting information is available regarding the stability of glucose concentrations in frozen plasma samples. Clinical trials could benefit from such long-term storage because it would allow usage of a central laboratory with higher-quality laboratory analyzers in contrast to mobile analyzers in a decentralized setting. Methods: In this study, venous blood samples were collected in lithium-heparin gel tubes. Plasma was separated immediately after blood was drawn, and from each of the 21 plasma samples, 6 aliquots were prepared for measurement at 6 time points: immediately and after 2, 4, 6, 8, and 12 weeks. Between sampling and measurement, aliquots were stored at less than −20°C. Transport on dry ice was simulated by placing aliquots in a −80°C freezer for 5 days between weeks 8 and 12. Measurements were performed on a hexokinase-based laboratory analyzer. Average relative differences and corresponding 99% confidence intervals (CIs) were calculated between the stored aliquots’ and the immediately measured aliquots’ glucose concentrations. Glucose concentrations were deemed stable as long as average relative differences were ≤±2.5%. Results: Over the whole 12-weeks duration, the largest average relative difference was −1.82% (99% CI: –2.25% to −1.39%). Shorter storage durations tended to lead to less bias. Conclusion: In this study, the stability of glucose concentrations in frozen plasma samples obtained with lithium-heparin gel tubes could be shown for up to 12 weeks. Future studies should be performed to assess whether this is independent of the glucose analyzer and the type of sampling tube used.

Coagulation testing: Comparison of portable (CoaguChek® XS) and automated coagulation analyzer in healthy cats

Background and Aim: The CoaguChek® XS (CCX) is a portable coagulation analyzer that is widely used to monitor prothrombin time (PT) in human patients taking oral anticoagulants. It can also be reliably used for screening dogs when PT is in the normal range. Efficacy of the portable CCX coagulation analyzer was evaluated for testing PT in healthy cats and the normal range was established. Materials and Methods: Blood samples of 82 cats were collected from the jugular vein and PT was measured using both the CCX and an automated coagulation analyzer (ACA). Spearman's correlation was used to measure the strength and direction of association between the two analyzers, while limits of agreement were assessed utilizing Bland-Altman analysis. Results: Range of PT using the CCX was 10.1-14.1 s. Correlation between the two analyzers was moderate but significant (r=0.3465, p=0.0014). Mean difference between CCX-PT and ACA-PT was 1.624 s and standard deviation was 0.890 with 95.1% of the samples falling within the limits of agreement. Conclusion: The CCX is a portable, easy to use coagulation analyzer that requires a small volume of blood and gives results within 1 min. Results showed moderate correlation and good agreement with a standard automated laboratory analyzer. The CCX can be used for screening coagulation testing when PT is in the normal range for cats. However, testing accuracy of the CCX in abnormal PT cats should be further investigated before diagnostic coagulopathy applications.

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.