Agreement between Coaguchek XS and STA-R Evolution (Hepato Quick) INR results depends on the level of INR

• We studied the agreement between Coaguchek XS (POC) and STA-R Evolution (Hepato Quick) INR results
• POC and laboratory results correlate well in the therapeutic range
• INR difference between POC and laboratory results increase with increasing INR
• The difference in thromboplastin source can explain the observed differences

IntroductionIntroducing point-of-care (POC) INR measurement to monitor anticoagulant therapy may be beneficial for both patients and anticoagulation clinics. However, agreement between POC and laboratory INR results is still unclear, especially at sub- and supratherapeutic levels. Therefore we investigated the analytical and clinical agreement between POC INR results of the Coaguchek XS and laboratory INR results of the STA-R Evolution.Materials and MethodsPaired POC and laboratory INR results were obtained and analyzed in 3257 patients aged 18–104 years between August 2008 and March 2014.ResultsMean difference between POC and laboratory results ranged from − 0.18 (95%CI − 0.20;-0.16) INR point for POC results 2.0-3.0, up to 1.14 (95%CI 0.87;1.42) INR point for POC results 7.1-8.0. In the therapeutic range (POC INR 2.0-4.0), mean difference between POC and laboratory results was − 0.13 (95%CI − 0.15;-0.12) INR point. At subtherapeutic (POC INR < 2.0) and supratherapeutic (POC INR > 4.0) INR levels, mean differences were − 0.13 (95%CI − 0.15;-0.11) and 0.72 (95%CI 0.63;0.80) INR point, respectively. Clinical agreement regarding therapeutic range was present in 92.0% (POC within range), 67.7% (POC below range) and 87.6% (POC above range) of the paired measurements. We observed ≥ 15% INR difference between the POC and laboratory result in 14.8% (POC INR 2.0-4.0), 17.0% (POC INR < 2.0) and 47.8% (POC INR > 4.0) of the paired measurements.ConclusionsPOC and laboratory INR results were strongly correlated within the therapeutic range and differences between results become larger with increasing INR. Clinical disagreement between laboratory and POC results occurs often at both sub- and supratherapeutic INR levels.