title: Comparative study of a portable system for prothrombin monitoring using capillary blood against venous blood measurements in patients using oral anticoagulants: correlation and concordance.
abstract: BACKGROUND
  Oral anticoagulants (OAC) are widely used in cardiology and are mainly indicated in cases of atrial fibrillation and prosthetic heart valves. Regular prothrombin time (PT) control is required for patients using OAC. New portable monitoring systems for measuring prothrombin time, eliminate the need to collect blood by venous puncture and facilitate daily life for these patients.
  
  
  OBJECTIVE
  To compare PT measurements using the Coaguchek S system with capillary blood and the standard method in venous blood.
  
  
  METHODS
  One hundred and twenty-seven patients from the Cardiology Institute's anticoagulation clinic underwent conventional blood collection and capillary blood collection via a finger prick for measurements using the Coaguchek S system.
  
  
  RESULTS
  The mean age was 58 +/- 14 years and 90% of the patients were white. OAC indications were atrial fibrillation (49.6%) and prosthetic heart valves (37.0%). The correlation coefficient, r s , was 0.90 (p<0.0001; CI:95% 0.87-0.93) between the Coaguchek S system and the control method. The Kappa measure of agreement among the patients with INR <2, INR between 2 and 3.5 and INR > 3.5 was 73.5%. The Coaguchek S system overestimated INR by 0.15 +/- 0.85 units. A great deal of discrepancy was found between the two techniques for INR values higher than 3.5 units.
  
  
  CONCLUSIONS
  The Coaguchek S system when compared to the control method revealed good correlation and a high degree of agreement for results lower than 4 units. However, confirmation is required for INR values above 3.5 using the standard method.
authors.affiliation: Serviço de Eletrofisiologia, Ambulatório de Anticoagulação, Instituto de Cardiologia do Rio Grande do Sul, Fundação Universitária de Cardiologia, Porto Alegre, RS, Brasil. editoração-pc@cardiologia.org.br
authors.forename: Tiago Luiz Luz
authors.initials: TL
authors.lastname: Leiria
authors.forename: Lúcia Campos
authors.initials: LC
authors.lastname: Pellanda
authors.forename: Eros
authors.initials: E
authors.lastname: Magalhães
authors.forename: Gustavo Glotz de
authors.initials: GG
authors.lastname: Lima
mesh_terms: D000284:Administration, Oral; D000925:Anticoagulants / Q000627:therapeutic use*; D001777:Blood Coagulation / Q000187:drug effects*; D002196:Capillaries; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D006331:Heart Diseases / Q000097:blood / Q000188:drug therapy*; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D011517:Prothrombin Time / Q000379:methods*; D014680:Veins
chemical_list: D000925:Anticoagulants