Biomedical subjects

J Vincelette

Publications and source records attributed to J Vincelette.

At least 19 recordsLinked to original sources

PubMed2007

HIV and ethnicity in Canada: is the HIV risk-taking behaviour of young foreign-born MSM similar to Canadian born MSM?

There is a dearth of information on the HIV risk-taking behaviour of foreign-born men who have sex with men (MSM) in Canada. This study focused on identifying sexual risk behaviour among MSM who immigrated to Canada and compared them to MSM who were born in Canada. Baseline data from the Omega Cohort in Montreal and the Vanguard Project in Vancouver were combined to form four ethnicity/race analytical categories (n = 1,148): White born in Canada (WBIC), White born outside of Canada, non-White born in Canada (NBIC) and non-White born outside of Canada (NBOC). Psychological, demographic and sexual behaviour characteristics of the groups were similar except: NBOC were more likely to be unemployed, less likely to be tattooed, had fewer bisexual experiences and less likely worried of insufficient funds. WBOC were more likely to report unprotected sex with seropositives and more likely to have had unprotected sex while travelling. NBIC were more likely to have ever sold sex and to have had body piercing. WBOC are at high risk of acquiring as well as transmitting HIV. It is important to consider place of birth in addition to ethnicity when developing programmes to prevent the transmission of HIV.

Adolescent↗

PubMed2002

Risk behaviours and prevalence of Chlamydia trachomatis and Neisseria gonorrhoeae genital infections among Montreal street youth.

We estimated the prevalence of Chlamydia trachomatis and Neisseria gonorrhoeae genital tract infections among 302 Montreal street youth (223 boys) and identified associated risk factors. Study participants, 14-25 years old (average 20.9 years), meeting specific criteria for homelessness, were recruited in street youth agencies. Participation included a structured interview and provision of a urine specimen. Among sexually active youth, (n = 300) 30.0% had more than five heterosexual partners and 13.0% had at least one homosexual partner (last year), 10.7% had received money in exchange for sex (last six months) and 47.0% reported sexual relations resulting in pregnancy (lifetime). Among all youths, 82.1% had used at least one type of illicit drug, and 30.1% injected drugs at least once (last six months). The prevalence of C. trachomatis infection was 6.6% (95% CI 4.1-10.0%). Prevalence did not vary significantly by sex, age or any other variable, except history of pregnancy (10.4% among youth with history of pregnancy vs 3.6% among others, P = 0.02). No cases of N. gonorrhoeae infection were found.

Adolescent↗

PubMed2001

Risk factors for hepatitis C virus infection among street youths.

BACKGROUND: The relative contributions to risk of hepatitis C virus (HCV) infection resulting from unsafe sexual behaviours and exposures to blood (e.g., tattooing, body piercing and injection drug use) among youths at risk are not well known. We interviewed street youths about risk factors for HCV infection and documented their HCV antibody status. METHODS: From December 1995 to September 1996 we recruited 437 youths aged 14 to 25 years who met specific criteria for itinerancy. Data on sociodemographic characteristics and lifetime risk factors were obtained during a structured interview, and a venous blood sample was taken for HCV antibody testing. RESULTS: Many of the subjects reported behaviours that put them at risk for blood-borne diseases: 45.8% had injected drugs, 56.5% had at least 1 tattoo, and 78.3% had body piercing. The overall prevalence of HCV infection was 12.6% (95% confidence interval [CI] 9.7%-15.9%). In a multivariate logistic regression analysis, injecting drugs (adjusted odds ratio [OR] 28.4 [95% CI 6.6-121.4]), being over 18 years of age (adjusted OR 3.3 [95% CI 1.6-7.0]) and using crack cocaine (adjusted OR 2.3 [95% CI 1.0-5.3]) were independent risk factors for HCV infection. Having more than 1 tattoo (adjusted OR 1.8 [95% CI 0.95-3.6]) was marginally associated with HCV infection, and body piercing was not. INTERPRETATION: Drug injection was the factor most strongly associated with HCV infection among street youths. Given that injection drug users are the driving force of the HCV infection epidemic in Canada, increased intervention efforts to prevent initiation of drug injection are urgently needed to curb the epidemic.

Adolescent↗

PubMed2001

Risk factors associated with HIV infection among young gay and bisexual men in Canada.

OBJECTIVE: To assess risk factors associated with HIV prevalence and incidence among gay and bisexual men in two prospective Canadian cohorts. METHODS: The Vanguard Project and the Omega Cohort are prospective cohort studies of gay and bisexual men ongoing in Vancouver and Montreal, respectively. For this analysis, baseline sociodemographic characteristics, sexual behavior, and substance use data from these two cohorts were combined. Assessment of risk factors for HIV seroprevalence and seroconversion were carried out using univariate and multivariate analysis. RESULTS: This analysis was based on 1373 gay and bisexual men aged 16 to 30 years. Men who were HIV-seropositive at baseline (n = 48) were more likely to report living in unstable housing, to have had less than a high school education, and to have been unemployed than those who were HIV-negative (n = 1325). HIV-positive men were also more likely to report having engaged in sexual risk behavior, including having had consensual sex at a younger age, having had at least 6 partners during the previous year, ever having been involved in the sex trade, and having engaged in unprotected receptive anal intercourse. With respect to substance use, HIV-positive men were more likely to report the use of crack, cocaine, heroin, and marijuana and to use injection drugs. Similarly, men who seroconverted during the course of the studies (n = 26) were more likely to report having less than a high school education and having lived in unstable housing at baseline. Compared with HIV-negative men, men who seroconverted were more likely to report ever having been involved in the sex trade and engaging in unprotected receptive anal intercourse. Reports of cocaine use and injection drug use were also significantly higher for men who seroconverted compared with HIV-negative men. CONCLUSIONS: Our data indicate that HIV-positive gay and bisexual men are more likely to be living in unstable conditions and to report more risky sexual and substance use behaviors than HIV-negative men.

Adolescent↗

PubMed2001

Sex-specific determinants of HIV infection among injection drug users in Montreal.

BACKGROUND: Sex-specific issues have not been extensively addressed in studies of HIV prevalence, despite the strong implications of differences between men and women in the risk of HIV transmission. The objective of this study was to examine sex-specific behaviours associated with HIV infection among injection drug users in Montreal. METHODS: A total of 2741 active drug users (2209 [80.6%] men) were recruited between 1988 and 1998. Information was sought on sociodemographic characteristics, drug-related behaviour and sexual behaviour, and participants were tested for HIV antibodies. Sex-specific independent predictors of HIV prevalence were assessed by stepwise logistic regression. RESULTS: The overall prevalence of HIV among study subjects was 11.1%; the prevalence was 12.0% among men and 7.5% among women. In multivariate models, a history of sharing syringes with a known seropositive partner (odds ratio [OR] for men 2.44, 95% confidence interval [CI] 1.72-3.46; OR for women 3.03, 95% CI 1.29-7.13) and of sharing syringes in the past 6 months (OR for men 0.61, 95% CI 0.44-0.85; OR for women 0.32, 95% CI 0.14-0.73) were independently associated with HIV infection. Other variables associated with HIV infection were homosexual or bisexual orientation, cocaine rather than heroin as drug of choice, frequency of injection drug use, and obtaining needles at a pharmacy or through needle exchange programs (for men only) and obtaining needles at shooting galleries and being out of treatment (for women only). INTERPRETATION: These results support the hypothesis that risk factors for HIV seropositivity differ between men and women. These sex-related differences should be taken into account in the development of preventive and clinical interventions.

Adolescent↗

PubMed2001

Multicenter study of a commercial, automated polymerase chain reaction system for the rapid detection of Mycobacterium tuberculosis in respiratory specimens in routine clinical practice.

A cooperative study was conducted among six laboratories to compare the performance of the Cobas Amplicor (CA) polymerase chain reaction (PCR) system (Roche Molecular Systems, USA) for the detection of Mycobacterium tuberculosis with that of microscopy and culture in routine clinical laboratory diagnosis. A total of 5,221 decontaminated respiratory specimens were tested. The use of an internal control allowed detection of PCR inhibition in 144 (2.8%) specimens. Only two culture-positive samples were CA PCR inhibitory and therefore could not be detected by PCR testing. Of the 333 culture-positive specimens, 278 (83.5%) were positive by the CA PCR. Of the 4,744 culture-negative specimens, 52 (1.1%) were positive by the CA PCR. After analysis of discrepancies, 40 of the 52 culture-negative, CA PCR-positive specimens were classified as true positive. Thus, the overall sensitivities of culture, CA PCR and microscopy were 89.3%, 85.2% and 55.5%, respectively. The overall specificity of the CA PCR was 99.7%. Five of the six centers found similar performances for the CA PCR, with sensitivities ranging from 85.7 to 90.9%. The CA PCR was more sensitive for smear-positive samples, exhibiting overall sensitivities of 96.1% and 71.7% for smear-positive and smear-negative specimens, respectively. These results indicate that the Cobas Amplicor system enables microbiology laboratories with reasonable previous experience in molecular biology testing to perform PCR and to detect Mycobacterium tuberculosis in more than 70% of specimens obtained from infected patients.

Automation↗

PubMed2001

Evidence for a correlation between antibody-dependent cellular cytotoxicity-mediating anti-HIV-1 antibodies and prognostic predictors of HIV infection.

Using our gp120/41-expressing, NK cell activity-resistant CEM.NKR cell clones as targets in HIV-1-specific antibody-dependent cellular cytotoxicity (ADCC) assays, we demonstrate here that the serum titers of anti-HIV-1 ADCC antibodies bear a significant (P < 0.05) positive correlation with the peripheral blood CD4+ T cell counts and a negative one with the number of copies of HIV-1 RNA in the plasma of HIV-infected individuals. These findings underscore the importance of these antibodies as a protective immune parameter in these infections.

Antibody-Dependent Cell Cytotoxicity↗

PubMed2000

Risk behaviour change and HIV infection among injection drug users in Montreal.

OBJECTIVE: To investigate the independent association between changes in risk behaviour and HIV seroconversion risk among Montreal injection drug users (IDU). DESIGN: A longitudinal study of risk behaviour change and the maintenance of low-risk practices. At baseline and semi-annually, subjects were tested for HIV, and questionnaires on risk behaviour were completed. RESULTS: A total of 833 IDU were recruited from January 1992 to June 1998, and completed a minimum of three visits. Large fluctuations in risk behaviour were observed, and the risk of HIV infection appeared to be dependent upon the consistency of risk behaviour practised. IDU who consistently engaged in risky behaviour were at high risk of HIV infection. IDU who attempted to practise low-risk behaviour but experienced relapses to risky behaviour were also at considerable risk of infection. IDU who managed to maintain low-risk practices were at minimal risk. Using Cox regression analysis, the hazard ratio (HR) of HIV seroconversion among IDU who consistently and inconsistently shared needles with an HIV-positive partner was 8.17 (95% CI 3.59-18.59) and 2.63 (95% CI 1.33-5.17), respectively, relative to non-needle sharers. Corresponding HIV incidence rates were 30.42 per 100 person-years (py) among consistent sharers, 13.78 per 100 py among inconsistent sharers and 2.51 per 100 py among non-sharers. CONCLUSION: Although some HIV risk reduction was evident, behaviour change seems to be effective only in IDU who adopt and maintain low-risk practices. Additional strategies may be needed to assist IDU in the maintenance of low-risk practices.

Adolescent↗

PubMed2000

Correlates of risky behaviors among young and older men having sexual relations with men in Montréal, Québec, Canada. Omega Study Group.

OBJECTIVE: To assess characteristics associated with 1) age and 2) recent unprotected anal sex with casual partners among men having sexual relations with men (MSM) participating in the Omega Cohort, Montréal, Québec, Canada. METHODS: The Omega Cohort is a study of the incidence and psychosocial determinants of HIV infection among MSM living in Montréal. MSM complete a questionnaire and are tested for HIV every 6 months. RESULTS: Thirteen percent of young MSM (< 30 years of age, n = 355) and 12% of older MSM (> or = 30 years of age, n = 455) reported recent unprotected anal sex with casual partners. The predictors of this latter behavior were: not living with a male sexual partner, unprotected anal sex with regular partner, > 5 casual partners, alcohol/drug use before anal sex, and having difficulties with procedures needed for safe sex. Among young MSM, additional predictors were: to have been living in Montreal for less than 1 year and to have exchanged money for sex. Among older MSM, additional predictors were: female sexual partners, unprotected anal sex with an HIV-infected partner, and feeling invulnerable to AIDS. CONCLUSION: Young Omega participants do not have more risky behaviors than older participants. Some predictors of recent risk behaviors with casual partners were different between the two groups. Prevention programs should be adapted consequently.

Adolescent↗

PubMed2000

Multicenter comparison of Roche COBAS AMPLICOR MONITOR version 1.5, Organon Teknika NucliSens QT with Extractor, and Bayer Quantiplex version 3.0 for quantification of human immunodeficiency virus type 1 RNA in plasma.

The performance and characteristics of Roche COBAS AMPLICOR HIV-1 MONITOR version 1.5 (CA MONITOR 1.5) UltraSensitive (usCA MONITOR 1. 5) and Standard (stCA MONITOR 1.5) procedures, Organon Teknika NucliSens HIV-1 RNA QT with Extractor (NucliSens), and Bayer Quantiplex HIV RNA version 3.0 (bDNA 3.0) were compared in a multicenter trial. Samples used in this study included 460 plasma specimens from human immunodeficiency virus (HIV) type 1 (HIV-1)-infected persons, 100 plasma specimens from HIV antibody (anti-HIV)-negative persons, and culture supernatants of HIV-1 subtype A to E isolates diluted in anti-HIV-negative plasma. Overall, bDNA 3.0 showed the least variation in RNA measures upon repeat testing. For the Roche assays, usCA MONITOR 1.5 displayed less variation in RNA measures than stCA MONITOR 1.5. NucliSens, at an input volume of 2 ml, showed the best sensitivity. Deming regression analysis indicated that the results of all three assays were significantly correlated (P < 0.0001). However, the mean difference in values between CA MONITOR 1.5 and bDNA 3.0 (0.274 log(10) RNA copies/ml; 95% confidence interval, 0.192 to 0.356) was significantly different from 0, indicating that CA MONITOR 1.5 values were regularly higher than bDNA 3.0 values. Upon testing of 100 anti-HIV-negative plasma specimens, usCA MONITOR 1.5 and NucliSens displayed 100% specificity, while bDNA 3.0 showed 98% specificity. NucliSens quantified 2 of 10 non-subtype B viral isolates at 1 log(10) lower than both CA MONITOR 1.5 and bDNA 3.0. For NucliSens, testing of specimens with greater than 1,000 RNA copies/ml at input volumes of 0.1, 0.2, and 2.0 ml did not affect the quality of results. Additional factors differing between assays included specimen throughput and volume requirements, limit of detection, ease of execution, instrument work space, and costs of disposal. These characteristics, along with assay performance, should be considered when one is selecting a viral load assay.

Branched DNA Signal Amplification Assay↗

PubMed2000

An important proportion of genital samples submitted for Chlamydia trachomatis detection by PCR contain small amounts of cellular DNA as measured by beta-globin gene amplification.

We assessed the quality of genital samples submitted for Chlamydia trachomatis detection by PCR by a second PCR assay for the presence of human beta-globin DNA. Endocervical and urethral samples were first tested by the COBAS AMPLICOR C. trachomatis assay (Roche Diagnostic Systems) with an internal control and were then amplified for the presence of beta-globin DNA with primers PC04 and GH20. Samples that contained inhibitors were retested after dilution 1:10. A total of 407 genital samples (311 endocervical swabs from 311 women and 96 urethral swabs from 95 men and 1 woman) collected over a 1-month period were evaluated. The internal control could not be amplified, despite dilution, from 3 of 23 samples that were retested after dilution because of inhibition, leaving 404 samples that could be analyzed by PCR. Eleven samples tested positive for C. trachomatis. Thirty (7.4%) of the 404 samples were negative for beta-globin. Twelve of the 23 undiluted samples that contained inhibitors tested positive for beta-globin DNA. Amplification of beta-globin DNA in samples submitted for C. trachomatis detection by the COBAS AMPLICOR C. trachomatis assay demonstrated that an important proportion of the samples did not contain cellular DNA. Assessment of the quality of the samples for PCR analysis by beta-globin amplification is feasible but cannot replace use of the internal control.

Cervix Uteri↗

PubMed2000

Association of hepatitis B virus infection with other sexually transmitted infections in homosexual men. Omega Study Group.

OBJECTIVES: This study determined the prevalence and factors associated with hepatitis B virus (HBV) infection among men who have sex with men. METHODS: At the baseline visit of an HIV study among men who have sex with men, we asked about HBV vaccination status and tested for HBV markers. RESULTS: Of 625 subjects, 48% had received at least 1 dose of HBV vaccine. Of 328 unvaccinated men, 41% had 1 or more HBV markers. HBV prevalence increased markedly with age and was associated with many sexual and drug-related behaviors. In a multivariate model, 7 variables were independently associated with HBV infection: ulcerative sexually transmitted diseases (odds ratio [OR] = 10.1; 95% confidence interval [CI] = 2.6, 54); injection drug use (OR = 5.2; 95% CI = 1.2, 26); gonorrhea or chlamydia (OR = 4.0; 95% CI = 1.9, 8.9); sexual partner with HIV/AIDS (OR = 3.6; 95% CI = 1.8, 7.1); 50 or more casual partners (OR = 3.4; 95% CI = 1.6, 7.1); received money for sex (OR = 3.0; 95% CI = 1.2, 7.8); and 20 or more regular partners (OR = 2.5; 95% CI = 1.1, 6.1). CONCLUSIONS: In Montreal, men who have sex with men are at risk for HBV infection, but a substantial proportion remain unvaccinated; new strategies are required to improve coverage. Men who have sex with men and who have a sexually transmitted infection, especially a genito-ulcerative infection, appear to be at particularly high risk for HBV infection.

Adult↗

PubMed1999

Hepatitis B virus infection among street youths in Montreal.

BACKGROUND: Street youths are at high risk for many health problems, including sexually transmitted diseases and bloodborne infections. The authors conducted a cross-sectional anonymous study from December 1995 to September 1996 involving street youths in Montreal to estimate the prevalence of risk behaviours for hepatitis B virus (HBV) infection and of markers of past and present HBV infection. METHODS: Participants were 437 youths aged 14 to 25 meeting specific criteria for itinerancy who were recruited in collaboration with the 20 major street youth agencies in Montreal. Sociodemographic and lifetime risk factor data were obtained during a structured interview, and a blood sample was taken to test for HBV markers (hepatitis B surface antigen and antibodies to the hepatitis B core antigen). Univariate analyses and multivariate logistic regressions were conducted. RESULTS: The mean age of the subjects was 19.5 years; 69.3% (303/437) were males. Many subjects had high-risk behaviours: 45.8% (200/437) had injected drugs, 24.5% (107/436) had engaged in prostitution, and 8.7% (38/437) reported having a sexual partner with a history of unspecified hepatitis. The prevalence rate for one or both HBV markers was 9.2% (40/434) (95% confidence interval [CI] 6.7%-12.3%). Multivariate logistic regression analysis showed that being over 18 years of age (adjusted odds ratio [OR] 4.5, 95% CI 1.8-11.7), having injected drugs (adjusted OR 3.5, 95% CI 1.5-8.3) and having had a sexual partner who had unspecified hepatitis (adjusted OR 3.2, 95% CI 1.3-7.5) were all associated with HBV infection. INTERPRETATION: Street youths are at high risk for HBV infection. Early and complete HBV vaccination among this vulnerable population is urgently needed.

Adolescent↗

PubMed1999

Factors associated with hepatitis B vaccination among men having sexual relations with men in Montreal, Quebec, Canada. Omega Study Group.

OBJECTIVE: To determine factors associated with hepatitis B virus (HBV) vaccination status among HIV-uninfected men who have affective and sexual relations with men (MASM) in Montreal, Quebec, Canada. METHODS: The Omega Cohort is a study of the incidence and psychosocial determinants of HIV infection among MASM in Montreal. Participants complete a questionnaire and are HIV-tested every 6 months. At baseline, we also performed testing for HBV markers and collected data on HBV vaccination history. RESULTS: Forty-six percent of 653 participants had received at least one dose of HBV vaccination, whereas 28% were completely vaccinated. Lack of vaccination was associated with injection drug use, having > or =20 regular lifetime partners, living outside Montreal, not having sex in bathhouses, and not having consulted a physician aware of the participant's sexual orientation. Among vaccinated MASM, incomplete vaccination was associated with having <20 lifetime casual partners, trading sex for drugs, having given goods for sex, having had unprotected anal sex with regular partners, and having no history of a previous sexually transmitted disease. CONCLUSION: A significant proportion of Montreal's MASM, some of whom are at risk of contracting HBV through sexual and parenteral transmission, have not been vaccinated for HBV. Men who have affective and sexual relations with men should be educated about the risk of HBV transmission and the seriousness of the disease.

Adolescent↗

PubMed1999

Trends in antimicrobial resistance among clinical isolates of the Bacteroides fragilis group from 1992 to 1997 in Montreal, Canada.

The objective of the present study was to analyze the susceptibility profiles of 911 clinical strains of the Bacteroides fragilis group isolated from 1992 to 1997 in our institution in order to monitor susceptibility changes over time. Whereas the rates of resistance to metronidazole, imipenem, piperacillin-tazobactam, ticarcillin-clavulanic acid, penicillin, piperacillin, and cefoxitin remained essentially unchanged, there was a significant increase in the rates of resistance to clindamycin, which rose from 8.2% in 1992 to 19.7% in 1997 (P < 0.0004).

Bacteroides fragilis↗

PubMed1999

Multicenter evaluation of the fully automated COBAS AMPLICOR PCR test for detection of Chlamydia trachomatis in urogenital specimens.

The fully automated COBAS AMPLICOR CT/NG test for the detection of Chlamydia trachomatis was evaluated in a multicenter trial. Test performance was evaluated for 2,014 endocervical swab and 1,278 urine specimens obtained from women and for 373 urethral swab and 254 urine specimens obtained from men. Culture served as the reference test. Culture-negative, COBAS AMPLICOR-positive specimens that tested positive in a confirmatory PCR test for an alternative target sequence within the C. trachomatis major outer membrane protein gene were resolved as true positives. The overall prevalence of chlamydia was 4.3% in cervical swabs and 11.0% in urethral swabs from men. When the results for each specimen type were considered separately, the resolved sensitivities were 96.5% (83 of 86) for endocervical swab specimens, 95.1% (39 of 41) for urine specimens from women, 100.0% (41 of 41) for urethral swab specimens from men, and 94.4% (17 of 18) for urine specimens from men; the resolved specificities were 99.4% (1,912 of 1,924) for endocervical swab specimens, 99.8% (1,204 of 1,207) for urine specimens from women, 98. 5% (325 of 330) for urethral swab specimens from men, and 100.0% (236 of 236) for urine specimens from men. For the subset of patients from whom both swab and urine specimens were collected, the combined results for both specimen types were used to identify all infected patients. Using these combined reslts as criteria, the resolved sensitivities for the COBAS AMPLICOR test were 82.6% (38 of 46) for endocervical swab specimens, 84.4% (38 of 45) for urine specimens from women, 84.2% (16 of 19) for urethral swab specimens from men, and 89.5% (17 of 19) for urine specimens from men. In comparison, the sensitivity of culture was only 56.5% (26 of 46) for endocervical specimens and 63.2% (12 of 19) for urethral specimens from men. The internal control provided in the COBAS AMPLICOR test revealed that 2.9% of specimens were inhibitory when they were initially tested. Nevertheless, valid results were obtained for 99. 1% of specimens because 68.7% of the inhibitory specimens were not inhibitory when a second aliquot of the original sample was tested. Two additional COBAS AMPLICOR-positive specimens were detected by retesting inhibitory specimens. The COBAS AMPLICOR CT/NG test for the detection of C. trachomatis exhibited equally high sensitivities and specificities with both urogenital swab and urine specimens and, thus, is well-suited for use in screening.

Automation↗

PubMed1998

Multicenter evaluation of the COBAS AMPLICOR HCV assay, an integrated PCR system for rapid detection of hepatitis C virus RNA in the diagnostic laboratory.

The benefits shown by the recent introduction of PCR for the in vitro diagnosis of hepatitis C virus (HCV) infection has prompted the development of standardized, ready-to-use assays that can be implemented in routine clinical laboratories. We have evaluated the clinical performance of COBAS AMPLICOR HCV (COBAS), the first instrument system that allows the automation of HCV RNA amplification and detection, to determine its performance in the routine laboratory setting. More than 2,000 specimens collected at five centers were analyzed in parallel by the COBAS and the manual AMPLICOR HCV (AMPLICOR) tests, and the results were compared with the results for biochemical and serological markers of HCV. In this study the two PCR systems showed the same accuracy, with a concordance rate of 99.8%. As expected, the correlation between serology and PCR was not absolute because the presence of anti-HCV antibodies may be associated with a latent or past infection. On the other hand, if the presence of confirmed anti-HCV antibodies and elevated alanine aminotransferase levels are taken as the "gold standard," indicating an active, ongoing infection, the COBAS and AMPLICOR tests show high and comparable sensitivities (100%) and specificities (98%), with positive and negative predictive values of 100 and 97%, respectively. During the study no false-positive reactions were detected. The use of an internal control allowed the identification of inhibitory substances that prevented amplification for 0.3 and 0.4% of samples tested by the COBAS and AMPLICOR tests, respectively. Compared to the manual system, the COBAS system allowed a significant reduction of hands-on time and could improve the overall laboratory work flow. In conclusion, these results support the use of the COBAS and AMPLICOR tests for the molecular diagnosis of active HCV infections.

Hepacivirus↗

PubMed1997

High rates of HIV infection among injection drug users participating in needle exchange programs in Montreal: results of a cohort study.

Needle exchange programs (NEPs) are designed to prevent human immunodeficiency virus (HIV) transmission among injection drug users. Although most studies report beneficial effects in terms of behavior modification, a direct assessment of the effectiveness of NEPs in preventing HIV infection has been lacking. A cohort study was conducted to assess the association between risk behaviors and HIV seroprevalence and seroincidence among injection drug users in Montreal, Canada. The association between NEP use and HIV infection was examined in three risk assessment scenarios using intensive covariate adjustment for empirical confounders: a cross-sectional analysis of NEP use at entry as a determinant of seroprevalence, a cohort analysis of NEP use at entry as a predictor of subsequent seroconversion, and a nested case-control analysis of NEP participation during follow-up as a predictor of seroconversion. From September 1988 to January 1995, 1,599 subjects were enrolled with a baseline seroprevalence of 10.7%. The mean follow-up period was 21.7 months. The adjusted odds ratio for HIV seroprevalence in injection drug users reporting recent NEP use was 2.2 (95% confidence interval 1.5-3.2). In the cohort study, there were 89 incident cases of HIV infection with a cumulative probability of HIV seroconversion of 33% for NEP users and 13% for nonusers (p < 0.0001). In the nested case-control study, consistent NEP use was associated with HIV seroconversion during follow-up (odds ratio = 10.5, 95% confidence interval 2.7-41.0). Risk elevations for HIV infection associated with NEP attendance were substantial and consistent in all three risk assessment scenarios in our cohort of injection drug users, despite extensive adjustment for confounders. In summary, in Montreal, NEP users appear to have higher seroconversion rates then NEP nonusers.

Adult↗