Table 2.
Frequencies and Hepatitis C Virus Incidence Estimates for Baseline Characteristics by City (N = 1391)
| Characteristic | Baltimore (n = 288) | San Francisco (n = 398) | Montreal (n = 244) | Sydney (n = 294) | Amsterdam (n = 48) | Melbourne (n = 119) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No. (%) | IR | No. (%) | IR | No. (%) | IR | No. (%) | IR | No. (%) | IR | No. (%) | IR | |
| Overall HCV incidence | 108 (37) | 32.6 (26.8–39.8) | 137 (34) | 24.7 (20.4–29.9) | 94 (38) | 23.5 (18.8–29.4) | 66 (22) | 21.4 (16.7–27.3) | 17 (35) | 13.1 (7.0–24.3) | 32 (27) | 7.5 (4.6–12.3) |
| Median No. of study visits (IQR) | 13 (5–23) | … | 4 (3–7) | … | 8 (4–15) | … | 4 (2–5) | … | 17 (5–29) | … | 4 (3–8) | … |
| Loss to follow-up before 24 mo (n = 1020) | 112 (59) | … | 201 (68) | … | 61 (36) | … | 181 (78) | … | 9 (24) | … | 39 (38) | … |
| Biological sex | ||||||||||||
| Male | 141 (49) | 41.5 (32.0–54.0) | 265 (67) | 22.2 (17.5–29.3) | 197 (81) | 24.6 (19.3–31.3) | 200 (68) | 24.6 (19.3–31.3) | 35 (73) | 14.6 (7.3–29.3) | 78 (66) | 9.2 (5.3–15.8) |
| Female | 78 (27) | 60.0 (44.3–81.0) | 133 (33) | 30.4 (22.2–41.6) | 47 (19) | 19.0 (10.8–33.4) | 94 (32) | 19.0 (10.8–33.4) | 13 (27) | 9.2 (2.3–36.6) | 41 (35) | 4.2 (1.4–13.0) |
| Unknowna | 69 (24) | 1.0 (0.1–7.2) | 0 | … | 0 (0) | … | 0 (0) | … | 0 (0) | … | 0 (0) | … |
| Median age, y (IQR) | 25 (23–29) | 22 (20–26) | 31 (26–39) | 24 (20–28) | 27 (24–31) | 25 (22–28) | ||||||
| Education level | ||||||||||||
| High school or below | 0 (0) | … | 173 (44) | 25.7 (19.6–33.7) | 64 (26) | 29.0 (19.4–43.2) | 117 (40) | 29.0 (19.4–43.2) | 3 (6) | … | 31 (26) | 3.1 (0.8–12.3) |
| Completed high school or above | 0 (0) | … | 219 (55) | 22.4 (16.9–29.7) | 180 (74) | 21.7 (16.5–29.3) | 177 (60) | 21.7 (16.5–28.3) | 0 (0) | … | 16 (13) | 5.8 (1.5–23.4) |
| Unknowna | 288 (100) | … | 6 (1) | … | 0 (0) | … | 0 (0) | … | 45 (94) | … | 72 (61) | 10.6 (6.0–18.6) |
| Ethnicity | ||||||||||||
| White/ Caucasian | 147 (51) | … | 298 (75) | 25.7 (20.8–31.9) | 220 (90) | 24.1 (19.1–30.4) | 218 (74) | 24.1 (19.1–30.4) | 39 (81) | 12.6 (6.3–25.2) | 94 (79) | 5.9 (3.2–11.1) |
| Black/African | 39 (14) | … | 33 (8) | 20.2 (9.6–42.3) | 2 (1) | 40.2 (5.7–285.6) | 54 (18) | 40.2 (5.7–285.6) | 0 (0) | … | 16 (13) | 17.3 (7.2–41.1) |
| Indigenous/ Native American | 0 (0) | … | 9 (2) | 20.8 (5.2–83.3) | 8 (3) | 26.4 (6.6–105.6) | 13 (4) | 26.4 (5.6–105.6) | 0 (0) | … | 6 (5) | … |
| Mixed or other | 2 (1) | … | 52 (13) | 24.0 (13.9–42.2) | 6 (2) | 23.5 (5.9–93.9) | 7 (2) | 23.5 (5.9–93.9) | 5 (10) | 13.2 (1.9–93.8) | 0 (0) | … |
| Unknowna | 100 (45) | … | 6 (1) | … | 8 (3) | 7.0 (1.0–49.9) | 2 (1) | … | 4 (8) | 18.5 (2.6–131.4) | 3 (3) | 21.7 (3.1–154.0) |
| History of prison sentence | ||||||||||||
| No | 0 (0) | … | 79 (20) | 22.1 (14.1–34.6) | 64 (26) | 21.1 (13 .3–33 .5) | 78 (27) | 13.8 (8.0–23.8) | 0 (0) | … | 87 (73) | 8.4 (4.9–14.5) |
| Yes | 0 (0) | … | 316 (80) | 24.6 (19.8–30.5) | 180 (73) | 24.4 (18 .9–31 .4) | 56 (19) | 4.5 (1.5–13.9) | 20 (42) | 2.6 (0.4–18.6) | 32 (27) | 5.1 (1.6–15.8) |
| Unknowna | 288 (100) | … | 3 (<1) | … | 0 (0) | … | 160 (54) | 34.7 (26.2–46.1) | 28 (58) | 23.5 (12.2–45.2) | 0 (0) | … |
| Recent unstable housing | ||||||||||||
| No | 0 (0) | … | 59 (15) | 17.6 (9.2–33.8) | 91 (37) | 18.6 (12.4–27.8) | 100 (34) | 9.0 (5.0–16.3) | 26 (54) | 7.0 (2.3–21.8) | 76 (63.9) | 7.93 (4.4–14.3) |
| Yes | 0 (0) | … | 329 (82.7) | 24.9 (20.3–30.6) | 153 (62.7) | 26.7 (20.4–35.0) | 194 (66) | 30.0 (22.9–39.2) | 17 (35.4) | 6.7 (1.7–26.7) | 43 (36.1) | 6.6 (2.8–16.2) |
| Unknowna | 288 (100) | … | 10 (2) | … | 0 (0) | … | 0 (0) | … | 5 (10) | … | 0 (0) | … |
| Recent unemployment | ||||||||||||
| No | 0 (0) | … | 94 (24) | 25.4 (16.9–38.2) | 153 (63) | 26.3 (20.0–34.5) | 77 (26) | 28.5 (18.2–44.6) | 0 (0) | … | 49 (41) | 3.5 (1.1–10.7) |
| Yes | 0 (0) | … | 286 (72) | 23.9 (19.1–30.0) | 72 (30) | 15.7 (9.8–25.3) | 83 (28) | 40.6 (28.2–58.4) | 0 (0) | … | 69 (58) | 11.3 (6.6–19.5) |
| Unknowna | 288 (100) | … | 19 (5) | 32.9 (15.7–69.0) | 19 (8) | 37.1 (18.5–74.1) | 134 (46) | 9.6 (6.1–16.2) | 48 (0) | … | 1 (<1) | … |
| HIV status | ||||||||||||
| Positive | 0 (0) | 7 (2) | 20.4 (5.1–81.6) | 1 (1) | … | 0 (0) | … | 0 (0) | … | 0 (0) | … | |
| Negative | 0 (0) | 265 (67) | 23.7 (18.8–29.9) | 241 (98) | 23.3 (18.6–29.2) | 134 (46) | 10.0 (6.1–16.2) | 35 (73) | 5.0 (1.6–15.6) | 67 (56) | 8.4 (4.4–16.2) | |
| Unknowna | 288 (100) | … | 126 (31) | 27.5 (19.6–38.7) | 2 (1) | 84.4 (11.9–598.8) | 160 (54) | 24.9 (19.0–32.5) | 13 (27) | 41.5 (19.8–87.2) | 52 (44) | 6.6 (3.2–13.9) |
| Median (IQR) duration of injection drug use, y | 4 (1–7) | 7 (3–13) | 4 (2–8) | 4 (1–8) | 6 (3–10) | |||||||
| ≤2 y | 0 (0) | … | 105 (26) | 24.3 (16.7–35.5) | 34 (14) | 35.3 (20.9–59.5) | 58 (20) | 35.3 (20.9–59.5) | 17 (35) | 19.9 (8.3–47.7) | 14 (12) | 13.7 (4.4–42.5) |
| >2 y | 0 (0) | … | 293 (73) | 24.8 (19.9–31.0) | 210 (86) | 21.9 (17.1–28.0) | 236 (80) | 21.9 (17.1–28.0) | 31 (65) | 9.7 (4.1–23.4) | 104 (87) | 7.2 (4.2–12.4) |
| Drug injected most often | … | |||||||||||
| Heroin | 0 (0) | … | 214 (54) | 27.4 (21.2–35.6) | 68 (28) | 12.4 (7.0–21.8) | 203 (69) | 25.3 (18.7–34.1) | 18 (38) | 17.9 (7.5–43.1) | 76 (64) | 8.3 (4.6–15.0) |
| Amphetamine/ methamphetamine | 0 (0) | … | 126 (32) | 17.5 (11.8–25.9) | 1 (1) | … | 70 (24) | 7.8 (3.4–17.3) | 5 (10) | … | 19 (16) | 10.4 (3.4–32.0) |
| Cocaine | 0 (0) | … | 9 (2) | 16.4 (4.1–65.5) | 121 (49) | 19.3 (13.5–27.6) | 6 (2) | 56.9 (31.5–102.8) | 5 (10) | 12.0 (1.7–85.5) | 1 (1) | … |
| Other opiates | 0 (0) | … | 3 (1) | 32.7 (4.6–232.1) | 50 (21) | 51.3 (34.4–76.6) | 14 (5) | 6.6 (0.9–46.8) | 0 (0) | … | 20 (17) | 5.5 (1.4–22.0) |
| Heroin + cocaine (combined) | 0 (0) | … | 28 (7) | 35.3 (19.6–63.8) | 5 (2) | … | 0 (0) | … | 17 (35) | 16.1 (6.1–43.0) | 0 (0) | … |
| Unknowna | 288 (100) | … | 18 (4) | … | 6 (2) | 38.7 (21.4–69.8) | 1 (<1) | 12.6 (7.4–21.2) | 3 (6) | … | 3 (2) | … |
| Recent receptive syringe sharing | ||||||||||||
| No | 0 (0) | … | 231 (58) | 18.4 (14.0–24.3) | 166 (68) | 22.5 (17.1–29.5) | 226 (77) | 22.5 (17.1–29.5) | 28 (58) | 9.3 (3.9–22.4) | 97 (82) | 6.3 (2.5–11.4) |
| Yes | 0 (0) | … | 147 (37) | 34.6 (26.1–45.8) | 76 (31) | 26.0 (17.6–38.5) | 68 (23) | 26.0 (17.6–38.5) | 7 (15) | 39.0 (16.2–93.7) | 22 (18) | 13.7 (5.7–33.0) |
| Unknown a | 288 (100) | … | 20 (5) | 71.6 (29.8–171.9) | 2 (1) | … | 0 (0) | … | 13 (27) | … | 0 (0) | … |
| Recent equipment sharing | ||||||||||||
| No | 0 (0) | … | 67 (17) | 15.8 (9.2–22.0) | 139 (57) | 22.5 (16.7–30.4) | 233 (79) | 22.5 (16.7–30.4) | 0 (0) | … | 47 (40) | 4.8 (2.0–11.5) |
| Yes | 0 (0) | … | 257 (65) | 28.1 (22.6–34.9) | 103 (42) | 24.9 (17.8–34.8) | 61 (21) | 24.9 (17.8–34.8) | 0 (0) | … | 1 (1) | … |
| Unknowna | 288 (100) | … | 74 (19) | 19.6 (10.6–36.5) | 2 (1) | … | 0 (0) | … | 48 (100) | 13.1 (7.0–24.3) | 71 (60) | 11.2 (6.2–20.3) |
| Recent opioid agonist therapy, including methadone and buprenorphine | ||||||||||||
| No | 0 (0) | … | 342 (86) | 24.2 (18.7–31.3) | 168 (69) | 26.4 (20.7–33.7) | 157 (53) | 26.4 (20.7–33.7) | 23 (48) | 19.9 (9.5–41.6) | 44 (37) | 8.4 (4.5–15.6) |
| Yes | 0 (0) | … | 50 (13) | 11.8 (3.8–36.6) | 75 (31) | 15.3 (8.9–26.3) | 137 (46) | 15.3 (8.9–26.3) | 25 (52) | 7.3 (2.3–22.6) | 75 (63) | 5.4 (2.2–12.9) |
| Unknowna | 288 (100) | … | 6 (2) | … | 1 (1) | … | 0 (0) | … | 0 (0) | … | 0 (0) | … |
| Recently obtained any needles/syringes from safe sourceb | ||||||||||||
| No | 0 (0) | … | 47 (12) | 6.9 (2.3–18.4) | 21 (8) | 8.6 (2.8–26.8) | 14 (5) | … | 0 (0) | … | 3 (3) | … |
| Yes | 0 (0) | … | 350 (88) | 27.7 (22.8–33.6) | 223 (92) | 25.3 (20.1–31.7) | 115 (39) | 10.8 (6.5–18.0) | 44 (92) | 13.0 (6.8–25.0) | 53 (45) | 4.5 (1.9–10.9) |
| Unknown a | 287 (100) | … | 1 (<1) | … | 0 (0) | … | 165 (56) | 24.9 (19.1–32.5) | 4 (8) | 13.7 (1.9–97.4) | 63 (53) | 11.3 (6.3–20.5) |
Incidence rates are shown as IR per 100 person-years (95% confidence interval), calculated using the quadratic approximation to the Poisson log likelihood for the log-rate parameter. Boldface values indicate significant difference at P < .05.
Abbreviations: HCV, hepatitis C virus; HIV, human immunodeficiency virus; IQR, interquartile range; IR, incidence rate; PY, person-years.
aData not collected by cohort or not reported by participant; the Baltimore cohort recruits and monitors young people who inject drugs for HCV infection, with a focus on serological data to assess the clinical characteristics of acute infection and reinfection. Because research goals focus on understanding questions related to immunology and virology, behavioral data were not systematically collected between 2000 and 2012. The Baltimore data server was compromised in 2005, leading to the loss of data on age and sex for some participants. Investigators preformed genome-wide association studies to obtain sex for participants who acquired HCV infection, but because age is not a genetic trait, age information was not recovered.
bSafe source defined as needle syringe program, needle exchange program, chemist/pharmacist, vending machine, mobile outreach.