Comparison between the conventional method and a portable device for determination of INR

Abstract

Context: Anticoagulation with warfarin is considered the appropriate treatment for venous thromboembolism and other thrombotic pathologies. Regular INR control is required for dosage adjustment and therapeutic control. Use of portable monitoring systems optimizes management of these patients. Objective: To compare INR measurements taken using the portable Coaguchek XS system in capillary blood with the standard laboratory method using venous blood. Method: Fifty-two samples each of venous and capillary blood were collected from nineteen patients on warfarin, who had been admitted to the Hospital da Beneficência Portuguesa de São Paulo, and analyzed using the conventional method and the Coaguchek XS system, respectively. Results: Spearman' s correlation coefficient (r) for the overall performance of the two methods was 0. 978 (p<0.0001; Exclusion criteria. samples were excluded if problems affected biological material collection.Determination of PT by the conventional method. 10 mL venous blood samples were collected into tubes containing 3.8% sodium citrate solution. Plasma was extracted from the samples by centrifugation at 3,800 rpm for 5±2 minutes and then the PT with INR was assayed using an ACL Elite Pro automated coagulation analyzer and a kit containing thromboplastin Recombiplastin 2G solution with an International Sensitivity Index (ISI) of 1.0.Determination of PT using the portable test. Samples of capillary blood were taken within one hour of collection of samples for the conventional method. Samples of approximately 10 µL were taken by finger stick from the finger pad of the first finger of patients' non-dominant hand, using Accu-Chek Safe-T-Pro Uno lancets. The blood drop was placed onto a Coaguchek XS PT test strip containing human recombinant thromboplastin with an ISI of 1.0 and the device displayed the result in approximately one minute.Classification of samples. The results for the 52 samples were classified by therapeutic range: INR < 2.0; INR 2.0 -3.5; or INR > 3.5.Ethical approval. The research project was approved by the Research Ethics Committee at the Hospital da Beneficência Portuguesa de São Paulo and all patients indicated their agreement to participation by signing consent forms. Statistical analysisThe INR results provided by the two different methods were analyzed for the entire sample and for the three subsets: INR <2.0; INR 2.0-3.5; and INR >3.5. The following analyses were performed: Student's t test for paired samples, Spearman's correlation index and the BlandAltman test, for evaluation of the differences between results. A 95% confidence interval and an α error of p<0.05 for statistical significance were adopted. Microsoft Excel 2007 was used for statistical analysis with the XLSTAT (trial version) and Analyze-it add-ins.

Efficacy of Point-of-Care for INR Testing Compared to Standard Laboratory Methods at a Tertiary Care Hospital in Saudi Arabia

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