Preanalytical variables and off-site blood collection: influences on the results of the prothrombin time/international normalized ratio test and implications for monitoring of oral anticoagulant therapy - van Geest-Daalderop, J H; Mulder, A B; Boonman-de Winter, L J; Hoekstra, M M; van den Besselaar, A M (Clin Chem, 2005)