Effectiveness and Safety of Therapy with Vitamin K Antagonists in Italian Patients Aged 80 Years or Older: a Multicentre Retrospective Study Comparing the Zeus Algorithm with the PARMA Algorithm or Manual Therapy.

The use of oral anticoagulant therapy (OAT) has constantly increased in the prevention of thromboembolism, particularly in patients 80 years of age or older. The aim of this multicentre study was to evaluate the efficacy and safety of vitamin K antagonists (VKAs) in elderly patients managed with a computer dosing algorithm compared with a dosage decided by expert physicians. Nine Italian thrombosis centres utilising the Zeus dosing algorithm were involved. The before-after study enrolled patients managed firstly by medical staff (manual system) or with the PARMA algorithm for 12 months from July 2008 to June 2009 and then with the Zeus algorithm during the analogous period from 2010 to 2011. Of 7605 patients in the OAT maintenance phase, 2281 were older than 80 years (mean age 84.2 years). Data for these 2281 patients managed with both modalities were analysed. Of the 2281 patients 80 years of age or older, 1776 underwent OAT for atrial fibrillation (AF). Use of a dosing algorithm increased the OAT quality: time in therapeutic range (TTR) was significantly (p < 0.001) higher during the Zeus period than during the manual period (71.6 vs. 68.8 %). The TTR achieved with Zeus was similar to that obtained with the PARMA algorithm. In addition, patients managed with Zeus took a weekly drug dosage significantly (p < 0.01) lower than that both suggested by PARMA and prescribed by expert physicians, with a reduced number of adverse events. This study confirms that the effectiveness and safety of VKA therapy in patients 80 years of age or older increases with computer dosing algorithms.