“… 12 , 13 , 61 One study used data from National Health Care Systems, 62 which may be resemble more the general population, although the proximity depends on how national systems of care are organized. Most samples are from hospitals, 55 , 57 , 59 , 63–65 outpatient departments, 66 , 67 or anticoagulation clinics, 68 , 69 which often reflect more selective samples. Designs also vary widely, including cross-sectional or registry studies, 52 , 54 , 57 cohort studies, 58 , 70 and systematic reviews, 71 limiting comparability.…”