Table A1.

Self-reported recent injecting risk behaviors in young IDU in San Francisco, 2000–2001.

	High-risk IDU (n=360)	Medium-risk IDU (n=162)	Low-risk IDU (n=322)
Median number of days injected, prior 30 (inter-quartile range)	25 (14–30)	20 (9–30)	20 (8–30)
Median typical number of injections per day injecting, prior 30 days (inter-quartile range)	3 (2–4)	2.5 (2–4)	2.5 (1.5–4)
Median # of injecting events, prior 30 days (number of days injected times usual number of injections per day injecting) (inter-quartile range)	69 (30–105)	45 (16–40)	42 (15–90)
Frequency of RNS* (prior 3 months)
Always	5%	---	---
Usually	7%	---	---
Sometimes	22%	---	---
Rarely	66%	---	---
Never	0%	100%	100%
Median imputed number RNS* events, prior 30 days (inter-quartile range)***	9 (4–15)	0	0
Median number of persons with whom engaged in RNS, prior 3 onths (inter-quartile range)	1 (1–2)	0	0
Frequency of AES** (prior 3 months)
Always	18%	22%	---
Usually	17%	19%	---
Sometimes	27%	60%	---
Rarely	21%	---	28%
Never	17%	---	72%
Median imputed number of AES** events, prior 30 days (inter-quartile range)***	12 (3–38)	17 (6–34)	0 (0–.7)
Median number of partners with whom pooled money to buy drugs, prior 3 months (inter-quartile range)****	3 (1–4)	2 (1–5)	2 (0–4)

^*RNS, receptive needle sharing

^**AES, ancillary equipment sharing

^***Imputations multiplied the total number of injections per month by the proportion of injecting events in which risk behavior occurred in the prior 3 months, where Always=1; Usually=.75, Sometimes=.25, Rarely=.1, Never=0

^****This variable is used as a proxy for number of persons with whom the IDU engaged in AES