Table 1.

Study design and size

	% (n = 47) articles
Study design
RCT*	11 (5)
Prospective cohort study	21 (10)
Database or other retrospective cohort	68 (32)
Reason for sample size
No reason given	77 (36)
Justified time interval (clinical or technology)	4 (2)
Trial size (RCT or cohort)	19 (9)
Power calculation reported	0 (0)
	Median (IQR) [range]
Eligible for study:
Number of patients (n = 35)	403 (148 to 833)
Number of events (n = 20)	112 (62 to 289)
Included in analysis:
Number of patients (n = 45)	342 (130 to 684)
Number of events (n = 33)	110 (61 to 230)
Number of events per candidate variable (n = 28)	10 (5 to 33) [2 to 95]

*RCT randomised controlled trial