Clinical drug trials in general practice: how well are external validity issues reported?

BMC Primary Care

Table 3 Reporting of trial sites, selection of patients, recruitment and completing fractions

	Trials reporting data n (%)	Median^a	IQR	Min-max	Mean	95% CI
Number of countries	106 (79)	10	7–15	1–45
Number of trial sites	122 (91)	96	61–171	1–1315
Number of patients screened	61 (46)	1284	615–2352	14–89,890
Number of patients enrolled	134 (100)	910	503–1743	13–29,019
Number of patients completed	125 (93)	648	379–1134	13–25,577
Recruitment fraction	61 (46)	0.66	0.46–0.83	0.17–1.00	0.64	(0.58–0.70)
Number needed to be screened	61 (46)	1.52	1.20–2.20	1.00–5.84	1.94	(1.64–2.22)
Completing fraction 1	125 (93)	0.83	0.70–0.89	0.19–1.00	0.78	(0.75–0.80)
Completing fraction 2	59 (44)	0.53	0.38–0.70	0.13–0.93	0.53	(0.47–0.58)

Definition of terms:
Recruitment fraction: Proportion of screened people who enrol in the trial (all enrolled/all screened), Number needed to be screened: Number of people screened in order to enrol one participant (1/recruitment fraction), Completing fraction 1: Proportion of participants who completed the trial (all completed/all enrolled), Completing fraction 2: Proportion of screened people who completed the trial (all completed/all screened), IQR: Inter-quartile range. CI: Confidence interval
^aMean not calculated for frequencies because of skewed data

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