Table 1.
Comparison of Baseline Interview Characteristics and Injection Risk Exposures of Study Participants Included in Analysis (n = 344) and Excluded From Analysis (n = 440)
| Participants Included (n = 344) | Participants Excluded (n = 440) | P Valuea | |
|---|---|---|---|
| Characteristic/Exposure | No. (%) | No. (%) | |
| Sex | .019 | ||
| Male | 212 (61.6) | 312 (70.9) | |
| Female | 102 (29.7) | 103 (23.4) | |
| Transgender or unreported | 30 (8.7) | 25 (5.7) | |
| Race/ethnicity | .158 | ||
| White/Caucasian/European American | 215 (62.5) | 310 (70.5) | |
| Black/African American | 12 (3.5) | 15 (3.4) | |
| Latino/a or Hispanic or Latin American | 16 (4.7) | 10 (2.3) | |
| Asian/Asian American/Filipino/a or Pacific Islander | 5 (1.5) | 3 (0.7) | |
| Native American | 7 (2.0) | 7 (1.6) | |
| Other | 89 (25.9) | 95 (21.6) | |
| Injected the following substance in the last 3 mob | |||
| Heroin | 246 (71.5) | 360 (81.8) | <.001 |
| Meth/amphetamine (speed) | 223 (64.8) | 256 (58.2) | .067 |
| Cocaine | 87 (25.3) | 123 (28.0) | .351 |
| Crack | 76 (22.1) | 109 (24.8) | .357 |
| Speedballs | 104 (30.2) | 168 (38.2) | .018 |
| Goofballs | 83 (24.1) | 109 (24.8) | .811 |
| Borrowed a used needle from another person (RNS) in last 3 mo | 113 (32.8) | 184 (41.8) | .010 |
| Engaged in receptive ancillary drug preparation equipment sharing in last 3 mo | 111 (32.3) | 185 (42.0) | .003 |
| Engaged in receptive backloading in last 3 mo | 208 (60.5) | 269 (61.1) | .709 |
| Needle used to backload was new (unused) | 68 (32.7) | 110 (40.9) | .263 |
| Median (IQR) | Median (IQR) | ||
| Age at enrollment, y | 24 (21–26) | 24 (21–26) | .219 |
| Age at first injection, y | 18 (16–21) | 17 (15–20) | .006 |
| Highest school grade completed | 12 (11–13) | 12 (10–13) | .489 |
| Days injected any substance including medication in past mo | 20 (6–30) | 20 (7–30) | .407 |
| No. of days injected substance in last moc | |||
| Heroin | 15 (4–30) | 18 (5–30) | .121 |
| Meth/amphetamine (speed) | 8 (3–15) | 5 (2–15) | .023 |
| Cocaine | 2 (1–4) | 2 (1–5) | .498 |
| Crack | 3.5 (1–7) | 2 (1–6) | .533 |
| Speedballs | 2 (1–7) | 3 (1–9.5) | .485 |
| Goofballs | 2 (1–5) | 2 (1–8) | .270 |
| Injections per day on injecting days in last mod | 3 (2–4) | 2. 5 (2–4) | .663 |
| No. of people with whom the subject injected in past moe | 3 (1–5) | 3 (2–6) | .240 |
| No. of people whose used needle the subject borrowed in the last 3 mof | 1 (1–2) | 1 (1–2) | .147 |
| No. of times engaged in RNS with the 3 people with whom subject injected (RNS) the most in the past mof,g | 2 (0–8) | 3 (1–7.5) | .346 |
Abbreviations: IQR, interquartile range; RNS, receptive needle sharing.
aChi-square test for categorical variables and Wilcoxon rank sum test (for comparison of medians) for continuous variables.
bTotal column percentage exceeds 100% due to participants reporting using more than 1 substance.
cAmong those who reported injecting the corresponding substance in the last 3 months.
dAmong those who reported injecting anything including medication in the last month (n = 560).
eAmong those who reported injecting with others at any point in the last 3 months (n = 528).
fAmong those who reported borrowing a previously used needle in the last 3 months (n = 204).
gNumber of times engaged in RNS in the last month: nij = nij1 + nij2 + nij3 for each participant, i, and each survey, j, where 1, 2, and 3 represent each of the 3 people with whom the participant reported engaging in RNS most frequently.