title: Comparative study of accuracy and clinical agreement of the CoaguChek XS portable device versus standard laboratory practice in unexperienced patients.
abstract: The objective of the study was to compare the accuracy and clinical agreement of the CoaguChek XS versus the standard laboratory practice. Forty-one patients on long-term anticoagulation with acenocumarol without previous experience in self-monitoring participated to obtain 218 pairs of data. Several methods for comparative statistics were applied to assess the possible disagreements between techniques as well as a range of previously published criteria of clinical agreement and the very recently described error-grid for INR comparison that we partially modify. The mean age was 52.1 and the indications for oral anticoagulation were prosthetic valves (36.59%), atrial fibrillation (34.15%), venous thromboembolic disease (21.95%) and others (7.31%) with a target range of 2-3 INR units (63.4%) or 2.5-3.5 (36.6%). Analyzing the whole series of data, the Pearsons rho correlation coefficient for precision between methods was 0.95 and the C(b) bias correction factor for accuracy 0.99 with a minimal bias of 0.1 INR units between methods applying the Bland-Altman plot. The linear regression procedure described by Passing and Bablok showed a minimal deviation from the best-fit line and a slope of 0.90. The mean of the absolute relative differences was 7% which is in the "very good" range of agreement. No results were found in the clinically "dangerous" D zone of the error-grids with 99% of data in the clinically irrelevant and low relevant areas A and B. In this study self-management with the CoaguChek XS was clinically safe and reliable.
authors.affiliation: Haematology Department, Monforte de Lemos Hospital, Monforte de Lemos, Spain. egomtor@gmail.com
authors.forename: Eduardo G
authors.initials: EG
authors.lastname: Torreiro
authors.forename: Elizabeth Gómez
authors.initials: EG
authors.lastname: Fernández
authors.forename: Rosa Mariño
authors.initials: RM
authors.lastname: Rodríguez
authors.forename: Carmen Vázquez
authors.initials: CV
authors.lastname: López
authors.forename: Julia Barreal
authors.initials: JB
authors.lastname: Núñez
mesh_terms: D000074:Acenocoumarol / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D000284:Administration, Oral; D000465:Algorithms; D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D001777:Blood Coagulation / Q000187:drug effects*; D019411:Clinical Laboratory Techniques; D016903:Drug Monitoring / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D019934:International Normalized Ratio / Q000295:instrumentation*; D016014:Linear Models; D008875:Middle Aged; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011934:Reagent Strips; D015203:Reproducibility of Results; D012648:Self Care / Q000295:instrumentation*
chemical_list: D000925:Anticoagulants; D011934:Reagent Strips; D000074:Acenocoumarol