“…2,13,14,17,[22][23][24][25][26][27][28] Research is usually conducted by investigators who are specialists working in academic centres; only the patients they care for have the possibility of being enrolled. 26 Patients are often further selected because of protocol inclusion and exclusion criteria. Investigators will often avoid enrolling elderly, frail patients with multiple comorbidities who are less likely to be able to comply with procedures.…”