Table 3.

Recruitment, retention and attrition rates by study centre and treatment arm

	Nott	Bris	New	Nor	Total	Nott	Bris	New	Nor	Total	Nott	Bris	New	Nor	Total	Nott	Bris	New	Nor	Total
	IPB+					IPB only					Control					Total
Baseline*
Parents approached	92	128	94	104	418	101	135	93	101	430	90	115	94	118	417	283	378	281	323	1,265
Passive refusal	0	20	2	10	32	0	34	2	15	51	0	12	2	22	36	0	66	6	47	119
Passive refusal rate	0%	16%	2%	10%	8%	0%	25%	2%	15%	12%	0%	10%	2%	19%	9%	0%	17%	2%	15%	9%
Active refusal	0	2	3	1	6	0	1	3	2	6	0	2	4	1	7	0	5	10	4	19
Active refusal rate	0%	2%	3%	1%	1%	0%	1%	3%	2%	1%	0%	2%	4%	1%	2%	0%	1%	4%	1%	2%
Total refusals	0	22	5	11	38	0	35	5	17	57	0	14	6	23	43	0	71	16	51	138
Total refusal rate	0%	17%	5%	11%	9%	0%	26%	5%	17%	13%	0%	12%	6%	20%	10%	0%	19%	6%	16%	11%
Incomplete consent form	1	1	0	0	2	0	0	0	1	1	1	0	0	0	1	2	1	0	1	4
Incomplete consent rate	1%	1%	0%	0%	0%	0%	0%	0%	1%	0%	0%	0%	0%	0%	0%	1%	0%	0%	0%	0%
Excluded/ ineligible	0	2	2	0	4	3	0	0	1	4	0	1	2	0	3	3	3	4	1	11
Excluded rate	0%	2%	2%	0%	1%	3%	0%	0%	1%	1%	0%	0%	2%	0%	1%	1%	1%	1%	0%	1%
Not recruited	1	25	7	11	44	3	35	5	19	62	1	15	8	23	47	5	75	20	53	153
Not recruited rate	1%	20%	8%	11%	11%	3%	26%	5%	19%	14%	0%	13%	9%	20%	11%	2%	20%	7%	16%	12%
Participants randomised	91	102	87	93	373	98	100	89	82	369	89	100	86	95	370	278	303	261	270	1,112
Recruitment rate	99%	80%	93%	89%	89%	97%	74%	96%	81%	86%	99%	87%	91%	81%	89%	98%	80%	93%	84%	88%
12-month follow-up**
Parents approached	89	96	75	92	352	95	97	78	79	349	87	97	80	95	359	271	290	233	269	1,060
Parents retained	59	68	56	58	241	59	74	55	64	252	61	69	50	78	258	179	211	161	200	751
Retention rate (% of those recruited)	65%	67%	64%	62%	65%	60%	74%	62%	78%	68%	69%	69%	58%	82%	70%	64%	70%	62%	74%	68%
Not approached	2	6	12	1	21	3	3	11	3	20	2	3	6	0	11	7	12	29	4	52
Not approached rate (% of those recruited)	2%	6%	14%	1%	6%	3%	3%	12%	4%	5%	2%	3%	7%	0%	3%	3%	4%	11%	1%	5%
Passive refusal	30	24	19	31	104	36	22	22	15	95	25	26	29	16	96	91	72	70	62	295
Passive refusal rate	34%	25%	25%	34%	30%	38%	23%	28%	19%	27%	29%	27%	36%	17%	27%	34%	25%	30%	23%	28%
Active refusal	0	4	0	2	6	0	1	1	0	2	1	2	1	1	5	1	7	2	3	13
Active refusal rate	0%	4%	0%	2%	2%	0%	1%	1%	0%	1%	1%	2%	1%	1%	1%	0%	2%	1%	1%	1%
Total refusals	30	28	19	33	110	36	23	23	15	97	26	28	30	17	101	92	79	72	65	308
Total refusal rate	34%	29%	25%	36%	31%	38%	24%	29%	19%	28%	30%	29%	38%	18%	28%	34%	27%	31%	24%	29%
Questionnaire lost	0	0	0	1	1	0	0	0	0	0	0	0	0	0	0	0	0	0	1	1
Total loss to follow-up	32	34	31	35	132	39	26	34	18	117	28	31	36	17	112	99	91	101	70	361
Attrition rate (% of those recruited)	35%	33%	36%	38%	35%	40%	26%	38%	22%	32%	31%	31%	42%	18%	30%	36%	30%	39%	26%	32%

IPB = Injury prevention briefing, Nott = Nottingham, Bris = Bristol, New = Newcastle, Nor = Norwich.

*The denominator for the rates at baseline is the number of parents approached to participate in the trial.

**The denominator for the rates at follow-up is the number of parents approached except where otherwise stated.