7 STUDY PROCEDURES 7.1 Study period This is the period between randomization (first testing with assigned test = Day 1) and final assessment of each individual. Data will be retrieved continuously as described above. After 3, 6, 9 and 12 months "interim" (safety, efficacy) analyzes will be performed (see Chapter 11). We will randomize 1200 clients of the AMC into two identically sized monitoring groups, Fiix-INR (test group) and INR (control group). Each individual will be assessed monthly for up to 24 months (an expected average of 18 months) until a total of 600 patients years of observation has been reached in each group. The study may also be stopped by the recommendation of the DSMB if a clinically significant difference in outcome becomes evident at an earlier time-point indicating inferiority of the new method.