High variability of HIV and HCV seroprevalence and risk behaviours among people who inject drugs: results from a cross-sectional study using respondent-driven sampling in eight German cities (2011–14)

Table 4 Details of the recruitment procedures using RDS in eight German cities, 2011-14

	Berlin	Essen	Leipzig	Frankfurt	Cologne	Hanover	Munich	Hamburg
	(n = 337)	(n = 197)	(n = 130)	(n = 285)	(n = 322)	(n = 252)	(n = 235)	(n = 319)
Target sample size	300-350	200	200	300	300	200-250	200	300
Month and year of recruitment	05-07. 2011	10-12. 2011	10-12.2012	01-03.2013	04-05.2013	07-09.2013	10-12.2013	03-05.2014
Time of recruitment	8 weeks	8 weeks	7 weeks	9 weeks	8 weeks	8 weeks	8 weeks	8 weeks
No. of study sites	4	1	2	2	1	1	1	1
No. of seeds in total	19	18	13	11	12	7	13	9
No. of unproductive seeds	4	6	4	2	0	4	3	0
Max. number of recruitment waves	13	10	8	20	13	14	14	20
Coupon received from partner	^a	^a	7 %	5 %	2 %	4 %	3 %	2 %
Coupon received from acquaintance	^a	^a	78 %	64 %	84 %	50 %	67 %	65 %
Coupon received from stranger	^a	^a	15 %	31 %	14 %	46 %	30 %	33 %

^adata on the relationship to the recruiter was not collected in first two study cities

ISSN: 1471-2458