Feasibility of self-sampled dried blood spot and saliva samples sent by mail in a population-based study

BMC Cancer

Table 1 Characteristics of the study participants

Overall (N = 4597)			Adequate/valid blood samples			Inadequate blood samples or did not return blood samples
			(N = 3038/66%)¹			(N = 1559/34%)
Variables	N	Mean (SD) ²	N	%	Mean (SD) ²	N	%	Mean (SD) ²
Age (years)	4573	57 (4.7)	3014		57 (4.1)	1559		57 (5.1)
50-54	1499		953	32		546	35
55-59	1528		1012	34		516	33
60-64	1409		963	32		446	29
65-69	137		86	3		51	3
Chi-square p-value⁵	0.045
Body mass index (kg/m ² ) ⁴	4243	25 (4.6)	2714		25 (4.4)	1529		25 (4.9)
<25	1562		1244	46		318	21
>25 < 29	1680		1082	40		598	39
>29	1001		388	14		613	40
Chi-square p-value⁵	<0.001
Education (in years)	4542		3013			1529
<=10	830		512	17		318	21
11-14	1830		1232	41		598	39
15+	1882		1269	42		613	40
Chi-square p-value⁵	0.007
Physical activity (less strenuous) ³	3661		2414			1247
Hours per week
0	86		47	2		39	3
1	422		275	11		147	12
2 to 3	1620		1082	45		538	43
4 to 5	917		605	25		312	25
6+	616		405	17		211	17
Chi-square p-value⁵	0.24
Physical activity (strenuous)	3557		2353			1204
Hours per week
0	1521		986	42		535	44
1	859		571	24		288	24
2 to 3	929		638	27		291	24
4 to 5	180		116	5		64	5
6+	68		42	2		26	2
Chi-square p-value⁵	0.32
Smoking	3649		2397			1252
Never	1583		1096	46		487	39
Current	778		431	18		347	28
Past	1288		870	36		418	33
Chi-square p-value⁵	<0.001

¹Adequate/valid samples were samples returned in an aluminium bag with a desiccant pouch while invalid samples were samples without a dessicant pouch or aluminium bag.
²Unadjusted mean and standard deviation.
³Physical activity: less strenuous = walking, bicycling, working in the garden more strenuous = aerobic, running, bicycling at high intensity.
⁴excluded women with height <125, and weight < 30 kg >170 kg.
⁵Compared the adequate (n = 3038) with the inadequate blood samples (n = 1559).

ISSN: 1471-2407