NIH Public Access
Author Manuscript
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
NIH-PA Author Manuscript
Published in final edited form as:
J Acquir Immune Defic Syndr. 2009 May 1; 51(Suppl 1): S42–S46. doi:10.1097/QAI.0b013e3181a265b2.
Predictors of Sexual Risk Reduction Among Mexican Female Sex
Workers Enrolled in a Behavioral Intervention Study
Steffanie A. Strathdee, PhD*, Brent Mausbach, PhD*, Remedios Lozada, MD†, Hugo StainesOrozco, MD‡, Shirley J. Semple, PhD*, Daniela Abramovitz, MS*, Miguel Fraga-Vallejo, MD§,
Adela de la Torre, PhD∥, Hortensia Amaro, PhD¶, Gustavo Martínez-Mendizábal, MD#, Carlos
Magis-Rodríguez, MD**, and Thomas L. Patterson, PhD*,††
*Division of Global Public Health, Department of Medicine, University of California, San Diego, La
Jolla, CA
Patronato Pro-COMUSIDA, Tijuana, Mexico
Facultad de Medicina, Universidad Autónoma de Ciudad Juárez, Mexico
NIH-PA Author Manuscript
§Facultad
de Medicina, Universidad Autónoma de Baja California, Mexico
∥Chicana/o
¶Bouvé
Studies, University of California, Davis, CA
College of Health Sciences, Northeastern University, Boston, MA
#Salud
y Desarollo Comunitario de Ciudad Juárez A.C. and Federación Méxicana de Asociaciones
Privadas, Ciudad Juárez, Mexico
**CENSIDA,
Ministry of Health, Mexico
Department of Psychiatry, University of California, San Diego, La Jolla, CA and Mental Illness
Research, Education and Clinical Care Program (MIRECC), San Diego Veterans Administration
Healthcare System, San Diego, CA.
Abstract
NIH-PA Author Manuscript
Objective—We recently showed efficacy of an intervention to increase condom use among female
sex workers (FSWs) in Tijuana and Ciudad Juarez, situated on the Mexico–United States border. We
determined whether increases in condom use were predicted by social cognitive theory and injection
drug user status among women randomized to this intervention.
Methods—Four hundred nine HIV-negative FSWs aged ≥18 years having unprotected sex with
clients within the prior 2 months received a brief individual counseling session integrating
motivational interviewing and principles of behavior change (ie, HIV knowledge, self-efficacy for
using condoms, and outcome expectancies).
Results—Increases in self-efficacy scores were associated with increases in percent condom use
(P = 0.008), whereas outcome expectancies were not. Female sex workers who inject drugs (FSWIDUs) increased condom use with clients but not to the same extent as other FSWs (P = 0.09). Change
in HIV knowledge was positively associated with change in percent condom use among FSW-IDUs
(P = 0.03) but not noninjection drug users.
Copyright © 2009 by Lippincott Williams & Wilkins
Correspondence to: Thomas L. Patterson, PhD, University of California, San Diego School of Medicine, 9500 Gilman Drive, MC 0680,
La Jolla, CA 92093−0680 (e-mail: tpatterson@ucsd.edu)..
Parts of the data treated in this article were presented at the 17th Annual Meeting of the International Society for Sexually Transmitted
Disease Research, July 29–August 1, 2007, Seattle, WA.
Strathdee et al.
Page 2
NIH-PA Author Manuscript
Conclusions—Increases in self-efficacy significantly predicted increased condom use among
FSWs, consistent with social cognitive theory. Increased HIV knowledge was also important among
FSW-IDUs, but their changes in condom use were modest. Enhanced interventions for FSW-IDUs
are needed, taking into account realities of substance use during sexual transactions that can
compromise safer sex negotiation.
Keywords
condom use; female sex workers; HIV; injection drug use; prostitution; self-efficacy
INTRODUCTION
In recent years, HIV prevalence has increased from less than 2% to 6% among female sex
workers (FSWs) in Tijuana and Ciudad Juarez, Mexico,1 which are adjacent to the US cities
of San Diego, CA, and El Paso, TX, respectively. There are an estimated 9000 FSWs in Tijuana,
2 and at least 4000 FSWs in Ciudad Juarez.3
NIH-PA Author Manuscript
HIV prevalence among female sex workers who inject drugs (FSW-IDUs) in Tijuana and
Ciudad Juarez is higher, at 14%,4 which is not surprising because these cities are situated on
major drug trafficking routes.5 Injection drug use has increased as local drug consumption
markets have emerged.6 The highest consumption of illegal drugs in Mexico is in Baja
California, whose largest city is Tijuana.7 Across Mexico, Ciudad Juarez ranks second only to
Tijuana in the number of illicit drug users, which is twice the national average.8
Based on 2 successful behavioral intervention studies with methamphetamine-using HIVpositive men who have sex with men (MSM) and HIV-negative heterosexuals,9,10 we designed
a behavioral intervention for Mexican FSWs consisting of a brief individual counseling session
integrating motivational interviewing and principles of social cognitive theory. The
intervention promoted skills to negotiate condom use among clients, but because the high
prevalence of substance use was not originally recognized, it did not take into account safer
sex negotiation within the context of substance use or safer injection behaviors.11 In a
randomized trial, we showed that this intervention significantly reduced incident HIV
infections and sexually transmitted infections (STIs) (ie, gonorrhea, Chlamydia, and syphilis).
12 Comparing intervention vs. control arms, we observed a 40% decline in STI cumulative
incidence. Incidence density for intervention vs. control was 13.8 vs. 24.92 per 100 personyears for cumulative STIs (P = 0.034) and 0 vs. 2.01 per 100 person-years for HIV (P = 0.0004),
with concomitant increases in total numbers and percentages of protected sex acts and
decreases in total numbers of unprotected sex acts with clients (P < 0.05).12
NIH-PA Author Manuscript
Few evaluations have dismantled HIV intervention effects to examine which theoretical
components are associated with successful behavioral outcomes13-16 and which subgroups
seem refractory to behavioral change. A priori, we hypothesized that reductions in unprotected
sex among FSWs randomized to the intervention would be mediated by increases in HIV
knowledge, self-efficacy (eg, confidence in one's ability to use condoms), and outcome
expectancies (eg, belief that using condoms successfully reduces the risk of acquiring HIV/
STIs), consistent with social cognitive theory.11 In addition to testing these hypotheses, we
determined whether efficacy of this intervention was reduced among FSW-IDUs, given that
high proportions of these FSWs reported that they and/or their clients use drugs during sexual
transactions.4
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
Strathdee et al.
Page 3
METHODS
Study Population
NIH-PA Author Manuscript
Between January 2004 and January 2006, outreach workers and municipal and community
health clinics recruited 924 FSWs in Tijuana and Ciudad Juarez into a behavioral intervention
study to increase condom use described in detail elsewhere.11 Eligibility requirements included
an age of at least 18 years and having traded sex for drugs, money, or other material benefit
within the previous 2 months. Participants were also required to have had unprotected vaginal
sex with at least 1 client in the past 2 months and were excluded if they had previously tested
HIV positive. After providing informed consent, an interviewer-administered survey was
conducted in Spanish in a private location. Participants also provided a blood draw and cervical
swab and were compensated US $30. Study protocols were approved by the Institutional
Review Boards in the United States and Mexico.
Randomization to either the intervention [“Mujer Segura” (healthy woman) intervention] or
the didactic control condition was performed on a weekly basis within each city using a fixed
computer-generated randomization scheme. Because the emphasis of the current article was
to determine within-group factors that predicted response to the intervention, the current
analysis was restricted to 409 FSWs randomized to the intervention arm.
NIH-PA Author Manuscript
Baseline Interview
Trained female counselors administered an interview covering a range of topics including
sexual risk behaviors, working conditions, financial need, victimization and trauma, use of
alcohol and illicit drugs, social support, social influence, life experiences, mood, self-esteem,
social cognitive factors, sociodemographic characteristics, and physical and psychiatric health
variables. The interview also addressed such behavioral outcomes as frequency of unprotected
sex with clients and spouse/steady partner, number of clients, number and type of other sex
partners (nonclients), self-reported number and type of STIs, and alcohol and drug use. The
follow-up survey was nearly identical but referred to behaviors taking place over the prior 6
months.
Mujer Segura Intervention
NIH-PA Author Manuscript
This intervention was based on pilot work in Tijuana17 and our experience conducting sexual
risk reduction interventions in the United States.9,10 A detailed description of the intervention
is given elsewhere.11 In brief, clinic-based health care staff and indigenous promotoras
(outreach workers) were trained as counselors to deliver a culturally sensitive sexual risk
reduction intervention that was tailored to the needs, values, beliefs, and behaviors of FSWs.
The intervention was based on social cognitive theory18 and sought to increase knowledge,
self-efficacy, and outcome expectancies regarding safer sex. To increase participants’
motivations to practice safer sex, we utilized motivational interviewing techniques (eg, key
questions, reflective listening, summarization, affirmation, and appropriate use of cultural
cues).19 The intervention focused on: (1) identifying motivations for practicing safer sex (eg,
protecting one's own health, avoiding STIs) and unsafe sex (eg, financial gain); (2) barriers to
condom use (eg, threat of physical violence, client refusal) and motivations for using condoms
(eg, to feel clean); (3) negotiation of safer sex with clients; and (4) enhancing social support.
Participants role-played interactions with clients and were asked to weigh advantages and
disadvantages of practicing the behavior using the “decisional balance” approach.19 Once
awareness of the problem was achieved and the balance began to shift in favor of positive
change, the participant and counselor developed an action plan and problem-solved barriers to
implementation.
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
Strathdee et al.
Page 4
Measures
NIH-PA Author Manuscript
Measures were translated into Spanish and back-translated into English. Behavioral outcomes
included frequency of unprotected sex with clients and protected sex ratio (number of protected
sex acts divided by total number of acts). FSWs also reported the number of times they engaged
in vaginal, oral, and anal sex without a condom (or dental dam) with clients and their spouse/
steady partner during the past month. Potential mechanism of change variables are described
below.
HIV/AIDS Knowledge
Our measure of knowledge20 consisted of 18 items, which assessed participants’ awareness of
the importance of condom use with respect to HIV prevention (eg, People who have been
infected with HIV quickly show serious signs of being infected; a person will not get HIV if
she or he is taking antibiotics). Response categories were True (1) or False (0). Total scores
on this measure corresponded to the number of items correctly answered.
Self-Efficacy
NIH-PA Author Manuscript
Our 5-item measure of self-efficacy11 asked participants to indicate the extent to which they
were able to use a condom properly with clients. Responses were coded on a 4-point scale (1
= strongly disagree to 4 = strongly agree), with an overall score corresponding to the mean
response to the 5 items.
Outcome Expectancies
Participants responded to 5 items using a 4-point scale ranging from 1 (strongly disagree) to 4
(strongly agree).11 An example of a positive outcome expectancy is: “I believe that condoms
will protect me from getting HIV.” Mean scores for the 5 items were calculated with higher
scores indicating more positive outcome expectancies.
Statistical Analysis
Before analyses, we calculated residualized change scores for 4 variables of interest: (a) HIV/
AIDS knowledge, (b) outcome expectancies, (c) self-efficacy for using condoms, and (d)
percent condom use with clients during vaginal and anal sex. There were no incident HIV cases
in the intervention arm and 23 incident STIs; low power thus precluded an assessment of the
mediating effects of theoretically important constructs on HIV/STI incidence. Similarly,
because we had only 12.5% power to examine the effect of injection drug user status on STI
incidence, this outcome was not studied here.
NIH-PA Author Manuscript
Residualized change scores were calculated by regressing postintervention values for these
variables onto their respective baseline values. Hierarchical linear regression was used to
analyze change in percent condom use from preintervention to post intervention. Block 1
consisted of 4 variables: (a) the number of years the participant had been a sex worker, (b)
whether or not she had >9 years of education, (c) whether or not she had children, and (d)
whether or not she had a history of injection drug use. In block 2, change in social cognition
constructs was entered, including changes in HIV knowledge, outcome expectancies, and selfefficacy. Block 3 consisted of interaction variables to determine if injection drug use moderated
the relations between change in social cognition variables and change in condom use behavior.
Therefore, this block consisted of the following interaction terms: (a) injection × change in
HIV knowledge, (b) injection × change in outcome expectancies, and (c) injection × change
in self-efficacy.
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
Strathdee et al.
Page 5
RESULTS
NIH-PA Author Manuscript
Of 409 FSWs who were randomized to the intervention, 66 (16.1%) had injected drugs. Overall,
342 (84%) returned for a 6-month follow-up visit. FSWs lost to follow-up were younger (P =
0.012), had experienced a shorter duration of sex work (P < 0.001), and had fewer episodes of
unprotected vaginal sex with clients within the past month but otherwise did not differ
significantly compared with FSWs who returned (Table 1).
With the exception of a slightly longer median duration of time since initiating sex work, FSWIDUs reported similar baseline characteristics to noninjectors (Table 1). In the overall sample,
median age was 32 years (interquartile range: 26.0−40.0), most had minimal formal education,
a quarter were married or living in common-law relationships, and most (92.4%) had children.
NIH-PA Author Manuscript
As seen our final model (Table 2), greater increase in self-efficacy was associated with greater
increase in percent condom use (t = 2.66, P = 0.008). This effect was not moderated by injection
drug use (t for interaction = 0.78, P = 0.44), suggesting that change in self-efficacy was
associated with change in condom use regardless of injection status. In contrast, there was a
significant interaction between injecting drug use and change in HIV knowledge (t = 2.13, P
= 0.034), suggesting that injection drug use may modify the relation between change in
knowledge and change in condom use. A post hoc analysis indicated that among FSW-IDUs,
change in knowledge was positively associated with change in percent condom use (t = 2.26,
P = 0.025). However, among FSWs who were noninjection drug users, change in HIV
knowledge was not significantly associated with change in percent condom use (t = 0.06, P =
0.950). Repeating all analyses controlling for site yielded no appreciable differences.
DISCUSSION
In examining the theoretical components of our intervention that were associated with
successful behavioral changes among Mexican FSWs, we report 3 central findings. First,
improvements in self-efficacy were predictive of significant increases in condom use with
clients among FSWs receiving the intervention. Second, although FSW-IDUs also reported
increased condom use, this subgroup benefited less from the intervention than noninjectors.
Third, FSW-IDUs who improved in HIV knowledge were more likely to increase condom use
with clients. Because our trial is one of the few to demonstrate significant improvements in
condom use among a high-risk sample of community-based women in a developing country
setting, these findings have important implications for translating this intervention from
research to practice and informing the design of future interventions.
NIH-PA Author Manuscript
Our behavioral intervention generated change in a theoretically important construct (ie, selfefficacy for using condoms), as it was originally designed.11 These findings support other
studies showing the importance of self-efficacy in increasing condom use among high-risk
HIV-negative women and girls,10,21,22 HIV-positive women,23,24 and substance users.9,15,
25
Future HIV interventions among high-risk women in these settings should target selfefficacy as an important intermediate end point in combination with HIV/STIs and assess
intervention fidelity by monitoring self-efficacy as a process measure.
In contrast, increases in outcome expectancies were not associated with a significant increase
in condom use among FSWs, which was also the case in our previous interventions with HIVnegative heterosexuals and HIV-positive MSM methamphetamine users.9,10 The reasons for
this are unclear but could suggest problems with measurement of this construct. It is also
possible that our measure of outcome expectancies may capture not only the belief in women's
ability to successfully negotiate condom use, but also reflect their personal perceptions and
partner-related barriers to condom use, which were shown as important predictors of condom
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
Strathdee et al.
Page 6
use among African American women.24 Couple-based studies of FSWs and their partners
would assist in addressing this issue.
NIH-PA Author Manuscript
Interestingly, FSW-IDUs who demonstrated increases in HIV knowledge were significantly
more likely to report increased condom use at follow-up, but this was not the case among
noninjectors. Although baseline HIV knowledge scores among FSW-IDUs were similar to
those of noninjectors, because FSW-IDUs are more marginalized, they may have been more
receptive to educational messages because they tended to encounter the health care system less
frequently.
NIH-PA Author Manuscript
Despite these findings, increases in condom use with clients were modest for FSW-IDUs. This
is not surprising because the important role of substance use in FSWs’ transactions with clients
in Tijuana and Ciudad Juarez was not anticipated when our intervention was designed.11 At a
minimum, our study suggests that FSW-IDUs require enhanced interventions that take into
account the disinhibiting effects of substance use on sexual behaviors and the extent to which
substance use occurring in the context of sex work may compromise judgment and the ability
to negotiate safer sex. Future interventions should integrate a harm reduction component
promoting both safer injection and safer sex negotiation. For example, Ross et al25 have
documented the need to alter both affective self-efficacy (ie, beliefs that condom use can be
sexually and emotionally satisfying) and situational self-efficacy (ie, the belief that condoms
could be used in challenging situations, such as when drunk or high) among substance using
populations. We are in the process of tailoring our intervention to address these critical needs
among FSW-IDUs in both border cities.
This study was limited somewhat by low power to detect significant interactions. Because our
follow-up period was relatively short, it is possible that intervention effects may have waned
over time. However, a similar brief intervention based on the same theoretical principles led
to sustained improvements more than 18 months among MSM in San Diego, CA.22 Although
outcomes in this analysis were self-reported, we previously showed that the behavioral changes
we observed were consistent with reductions in HIV and STI incidence, which is the ultimate
test of overall intervention effectiveness. Because we studied a relatively large number of FSWs
from 2 Mexico–United States border cities, our findings may not be generalizable elsewhere
in Mexico or to other countries. Strengths of our intervention include its brevity and its ability
to be delivered by trained counselors with little to no formal education. Our binational team,
together with Mexican health officials, is poised to translate this intervention and evaluate it
at a community level in an effort to ensure that the concentrated HIV epidemics in these cities
do not become generalized.
NIH-PA Author Manuscript
ACKNOWLEDGMENTS
The authors gratefully acknowledge the study staff and participants; Brian Kelly for editing assistance and the
following organizations for their cooperation: the Municipal and State Health Departments of Tijuana, Baja California,
and Ciudad Juarez, Chihuahua; Salud y Desarollo Comunitario de Ciudad Juarez A.C, Patronado Pro-COMUSIDA,
and Federación Méxicana de Asociaciones Privadas (FEMAP); and the Universidad Autónoma de Baja California
and Universidad Autónoma de Ciudad Juárez.
Supported by Grant numbers R01 MH065849, R01 DA023877, and R01 DA034477 from the National Institutes of
Health.
REFERENCES
1. Patterson TL, Semple SJ, Staines H, et al. Prevalence and correlates of HIV infection among female
sex workers in two Mexico-U.S. border cities. J Infect Dis 2008;197:728–732. [PubMed: 18260766]
2. Brouwer KC, Strathdee SA, Magis-Rodriguez C, et al. Estimated numbers of men and women infected
with HIV/AIDS in Tijuana, Mexico. J Urban Health 2006;83:299–307. [PubMed: 16736378]
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
Strathdee et al.
Page 7
NIH-PA Author Manuscript
NIH-PA Author Manuscript
NIH-PA Author Manuscript
3. Patterson TL, Semple SJ, Fraga M, et al. Comparison of sexual and drug use behaviors between female
sex workers in Tijuana and Ciudad Juarez, Mexico. Subst Use Misuse 2006;41:1535–1549. [PubMed:
17002992]
4. Strathdee SA, Philbin MM, Semple SJ, et al. Correlates of injection drug use among female sex workers
in two Mexico-U.S. border cities. Drug Alcohol Depend 2008;92:132–140. [PubMed: 17714888]
5. Bucardo J, Brouwer KC, Magis-Rodriguez C, et al. Historical trends in the production and consumption
of illicit drugs in Mexico: implications for the prevention of blood borne infections. Drug Alcohol
Depend 2005;79:281–293. [PubMed: 16102372]
6. Magis-Rodríguez, C.; Ruiz-Badillo, A.; Ortiz-Mondragón, R., et al. Estudio sobre prácticas de riesgo
de infección para VIH/SIDA en inyectores de drogas de la cd. de Tijuana B.C.. Biblioteca Virtual en
Salud VIH/SIDA. 2002 [March 16, 2009]. Available at: http://bvssida.insp.mx/articulos/2382.pdf.
7. Secretaría de Salud. Encuesta Nacional de Adicciones. 2002 [March 16, 2009]. Available at:
http://www.consulta.com.mx/interiores/99_pdfs/15_otros_pdf/ENA.pdf.
8. Bucardo J, Brouwer KC, Magis C, et al. Historical trends in the production and consumption of illicit
drugs in Mexico: implications for the prevention of blood borne infections. Drug Alcohol Depend
2005;79:281–293. [PubMed: 16102372]
9. Mausbach BT, Semple SJ, Strathdee SA, et al. Effectiveness of a behavioral intervention for increasing
safer sex behaviors in HIV+ methamphetamine users: results from the EDGE study. Drug Alcohol
Depend 2007;87:249–257. [PubMed: 17182196]
10. Mausbach BT, Semple SJ, Strathdee SA, et al. Efficacy of a behavioral intervention for increasing
safer sex behaviors in HIV-negative, heterosexual methamphetamine users: results from the fast-lane
study. Ann Behav Med 2007;34:263–274. [PubMed: 18020936]
11. Patterson TL, Semple SJ, Fraga M, et al. A sexual risk reduction intervention for female sex workers
in Mexico: design and baseline characteristics. J HIV AIDS Soc Serv 2006;5:115–137.
12. Patterson TL, Semple SJ, Lozada R, et al. Efficacy of a behavioral intervention to promote condom
use among female sex workers in two Mexican-U.S. border cities. Am J Public Health 2008;98:2051–
2057. [PubMed: 18799768]
13. Dunn C, Deroo L, Rivara FP. The use of brief interventions adapted from motivational interviewing
across behavioral domains: a systematic review. Addiction 2001;96:1725–1742. [PubMed:
11784466]
14. Johnson WD, Hedges LV, Diaz RM. Interventions to modify sexual risk behaviors for preventing
HIV infection in men who have sex with men. Cochrane Database Syst Rev 2003;(1):CD001230.
[PubMed: 12535405]
15. Semaan S, Des Jarlais DC, Malow R. Behavior change and health-related interventions for
heterosexual risk reduction among drug users. Subst Use Misuse 2006;41:1349–1378. [PubMed:
17002987]
16. Bryan A, Schmiege SJ, Broaddus MR. Mediational analysis in HIV/AIDS research: estimating
multivariate path analytic models in a structural equation modeling framework. AIDS Behav
2007;11:365–383. [PubMed: 16917669]
17. Patterson TL, Semple SJ, Fraga M, et al. An HIV prevention intervention for sex workers in Tijuana,
Mexico: a pilot study. Hisp J Behav Sci 2005;27:82–100.
18. Bandura, A. Social Foundations of Thought and Action: A Social Cognitive Theory. Prentice-Hall;
Englewood Cliffs, NJ: 1986.
19. Miller, WR.; Rollnick, S. Motivational Interviewing: Preparing People to Change Addictive Behavior.
Guilford Press; New York, NY: 1991.
20. Carey MP, Schroder KE. Development and psychometric evaluation of the brief HIV Knowledge
Questionnaire. AIDS Educ Prev 2002;14:172–182. [PubMed: 12000234]
21. Jemmott JB III, Jemmott LS, Fong GT, et al. Reducing HIV risk-associated sexual behavior among
African American adolescents: testing the generality of intervention effects. Am J Community
Psychol 1999;27:161–187. [PubMed: 10425698]
22. Villaruel AM, Jemmott LS, Jemmott JB III. Designing a culturally based intervention to reduce HIV
sexual risk for Latino adolescents. J Assoc Nurses AIDS Care 2005;16:23–31. [PubMed: 16438123]
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
Strathdee et al.
Page 8
NIH-PA Author Manuscript
23. Wingood GM, DiClemente RJ, Mikhail I, et al. A randomized controlled trial to reduce HIV
transmission risk behaviors and sexually transmitted diseases among women living with HIV: the
WiLLOW Program. J Acquir Immune Defic Syndr 2004;37(Suppl 2):S58–S67. [PubMed: 15385901]
24. Raiford JL, Wingood GM, Diclemente RJ. Correlates of consistent condom use among HIV positive
African American women. Women Health 2007;46:41–58. [PubMed: 18160369]
25. Ross MW, Timpson SC, Williams ML, et al. The impact of HIV-related interventions on HIV risk
behavior in a community sample of African American crack cocaine users. AIDS Care 2007;19:608–
616. [PubMed: 17505921]
NIH-PA Author Manuscript
NIH-PA Author Manuscript
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
Strathdee et al.
Page 9
TABLE 1
Baseline Characteristics of FSWs Who Inject and Do not Inject Drugs in Tijuana and Ciudad Juarez
Variable
NIH-PA Author Manuscript
Total (N = 409)
FSW-IDUs (n = 66)
Non-IDU (n = 343)
P
32 (26−40)
31 (27−35)
33 (26−41)
0.22
Median age (IQR), yr
4 (2−10)
5 (3−10)
4 (2−10)
0.03
>9 years of education (%)
Median no. years in sex work (IQR)
10.6
12.1
10.3
0.66
Has children (%)
92.4
93.9
92.1
0.80
Fellow FSWs use drugs/alcohol with
clients (%)
88.7
92.4
88.0
0.40
Median no. unprotected vaginal sex
acts with clients (last month) (IQR)
12 (4−26)
16 (6−34)
12 (4−24)
0.17
Median HIV knowledge score (IQR)
12 (10−14)
12.5 (11−14)
12 (10−14)
0.57
Median outcome expectancy score
(IQR)
2.6 (2.4−3)
2.7 (2.4−3)
2.6 (2.4−3)
0.93
Median self-efficacy score (IQR)
3.0 (2.75−3.25)
3 (2.5−3.5)
3 (2.75−3.25)
0.63
Median percent condom use (IQR)
61.4 (37.5−80.0)
60 (36.4−74.6)
62.5 (37.5−80.0)
0.47
52.8
50.0
53.3
0.69
85
84
85
0.86
Ever been tested for HIV
Returned for 6-month Follow-up
visit (%)
NIH-PA Author Manuscript
IDU, injection drug user; IQR, interquartile range.
NIH-PA Author Manuscript
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.
Strathdee et al.
Page 10
TABLE 2
Regression Model Predicting Change in Sexual Risk Behavior
Variable
NIH-PA Author Manuscript
Years in sex work
Block 1
Block 2
Block 3
0.003 (0.002)
0.003 (0.002)
0.003 (0.002)
>9 years of education
0.034 (0.049)
0.030 (0.048)
0.045 (0.048)
Has children
−0.100 (.064)
−0.100 (0.063)
−0.093 (0.062)
−0.102 (0.040)*
−0.093 (0.039)*
−0.106 (0.040)*
Change in HIV knowledge
—
0.005 (0.007)
0.000 (0.007)
Change in outcome expectancy
—
0.003 (0.036)
0.028 (0.040)
Change in self-efficacy
—
0.033 (0.009)*
0.027 (0.010)*
Inject-by-change in HIV knowledge
—
—
0.016 (0.025)*
Inject-by-change in outcome expectancy
—
—
−0.176 (0.105)
—
—
0.059 (0.024)
2.73*
4.01*
3.68*
Ever injected drugs
Inject-by-change in self-efficacy
F value
df
4286
7283
10,280
Total R square
0.037
0.084
0.105
NIH-PA Author Manuscript
Values outside parentheses are unstandardized coefficients. Values inside parentheses are standard errors.
*
P < 0.05.
NIH-PA Author Manuscript
J Acquir Immune Defic Syndr. Author manuscript; available in PMC 2009 August 29.