Continuing injecting risk behaviour: results from the Amsterdam Cohort Study of drug users

AIMS

To give a detailed description of injection-related risk behaviours, and to estimate the relative importance of these behaviours with regard to HIV transmission.

DESIGN

The present study was part of the Amsterdam Cohort Study of drug users.

SETTING

In Amsterdam, a city with extensive preventive measures, large HIV-risk reductions have taken place, but no further decreases have occurred since 1991.

PARTICIPANTS AND MEASUREMENTS

A detailed questionnaire on injecting risk behaviour was completed by a cross-section of participants in 1992/93 (n = 168). Among 48 HIV-seroconverters, a questionnaire was completed concerning possible HIV-transmission route.

FINDINGS

Of 96 HIV-negative participants, 23% deliberately borrowed a used syringe, 18% reported possible "accidental" borrowing, 9% front/backloading, 4% simultaneous injection, and 32% possible sharing of ancillary equipment. Of deliberate borrowers, 64% borrowed from a person with unknown or positive HIV serostatus, and 81% did not appropriately clean the equipment; 79% borrowed in the absence of serious withdrawal symptoms. Risk factors differed for deliberate and 'accidental' borrowing. Among the HIV seroconverters, the most likely transmission route was borrowing in 29% of cases, front/backloading in 8%, borrowing or front/backloading in 21%, unprotected sexual contact in 23% (mainly with regular partner) and either injecting or sexual risk in 13%. Women were much more likely to report sexual transmission (p = 0.016). Borrowing was admitted by 43% before, and 64% after awareness of HIV-seroconverion.

CONCLUSIONS

As the injecting risk is high, usually deliberate, and often in the absence of withdrawal symptoms, further prevention seems difficult. Although deliberate borrowing is the main risk for HIV seroconversion, unprotected sexual contacts and front- and backloading may be more important than previously thought in Amsterdam. Under-reporting of borrowing is probably substantial, but does not alter the above conclusions.

Geographical variation in disease progression in HIV-1 seroconverted injecting drug users in Europe?

BACKGROUND

Human immunodeficiency virus (HIV) disease progression might vary by geographical region due to differences in the spectrum of HIV-related illnesses and (access to) health care. Therefore, the effect of geographical region, next to the effect of other potential cofactors, on disease progression in 664 injecting drug users (IDU) with documented HIV seroconversion from eight cohorts in Europe was studied.

METHODS

Kaplan-Meier methods and Cox proportional hazards analysis were performed to assess the effect of geographical region, other sociodemographics, drug use and repeated HIV exposure on progression from HIV seroconversion to immunosuppression, AIDS and death with AIDS. We considered the confounding effect of study-design related factors (e.g. setting of follow-up), and accounted for pre-AIDS death from natural causes by imputing when each endpoint would have occurred, had they not died without AIDS.

RESULTS

Estimates of progression to AIDS and death with AIDS were substantially faster after taking pre-AIDS mortality into account. Median incubation time from seroconversion to the first CD4 count < 200 cells/microliter was 7.7 years (95% CI: 7.1-8.3) and to AIDS 10.4 years (95% CI: 9.8-infinity). The 10-year survival was 70.3% (95% CI: 62.8-76.6). The relative hazards (RH) of AIDS for IDU from central and southern Europe compared with IDU from northern Europe was 1.9 (95% CI: 1.2-3.0) and 1.2 (95% CI: 0.6-2.3), respectively, before, and 1.5 (95% CI: 0.7-3.2) and 1.1 (95% CI: 0.6-2.3) after taking differences in study-design related factors into account. Accounting for these factors, the RH of death with AIDS was 0.9 (95% CI: 0.3-2.5) for central and 1.2 (95% CI: 0.4-3.4) for southern Europe compared with northern Europe. For the first CD4 count < 200 cells/microliter these figures were 0.8 (95% CI: 0.5-1.4) and 0.8 (95% CI: 0.5-1.4). Age at seroconversion was the strongest predictor of disease progression. No statistically significant differences in disease progression were found by gender, foreign nationality, drug use and potential repeated HIV exposure.

CONCLUSIONS

We found no evidence for regional variability in HIV disease progression among European IDU. Future studies evaluating geographical differences should consider the confounding effect of study-design related factors and differential non-AIDS mortality. As age is an important determinant of disease progression, it should be considered in recommending treatment.

Pre-AIDS mortality and morbidity among injection drug users in Amsterdam and Baltimore: an ecological comparison

Mortality and morbidity between injecting drug users in Amsterdam (n = 624) and Baltimore (n = 2,185) are compared to generate a hypothesis about the role of different health care systems and drug user policies (universal care and harm reduction versus episodic care and criminalization, respectively). Overdose/suicide mortality was twofold higher in Amsterdam; no sufficient explanation was found. Other independent "risk factors" for overdose/suicide mortality were recent injecting, polydrug use, and HIV-seropositivity (especially with CD4 count < 200/mm3). High dose methadone maintenance was associated with lower mortality. Incidence of hospitalizations and emergency room visits was substantially lower in Amsterdam, suggesting that higher accessibility to primary care in Amsterdam lowers (inpatient) hospital visits and presumably societal costs.

New evidence to reconcile in vitro and epidemiologic data on the possible role of heroin on CD4+ decline among HIV-infected injecting drug users

Long-term effects of drug type and other drug use related risk factors on CD4+ cell decline were assessed in 224 HIV-infected injecting drug users (IDUs) from Baltimore (ALIVE), USA, and 63 IDUs from Amsterdam, The Netherlands. Higher frequencies of borrowing used injection equipment since 1980 resulted in a higher CD4+ count already present before seroconversion (P = 0.049). Use of mainly heroin in the seroconversion interval resulted in a sharper CD4+ decline until the first 6 months after seroconversion (P = 0.004), but CD4+ values converged later on. This finding might reconcile earlier discordant epidemiological and laboratory study results regarding the possible effects of heroin.

No evidence for an effect of the CCR5 delta32/+ and CCR2b 64I/+ mutations on human immunodeficiency virus (HIV)-1 disease progression among HIV-1-infected injecting drug users

The relationship between CCR5 and CCR2b genotypes and human immunodeficiency virus (HIV)-1 disease progression was studied among the 108 seroconverters of the Amsterdam cohort of injecting drug users (IDUs). In contrast to earlier studies among homosexual men, no effect on disease progression of the CCR5 Delta32/+ and the CCR2b 64I/+ genotypes was found, when progression to AIDS, death, or a CD4 cell count <200/microL was compared by a Cox proportional hazards model. Furthermore, CD4 cell decline (by a regression model for repeated measurements) and virus load in the first 3 years after seroconversion did not differ between the CCR5 and CCR2b wild type and heterozygous genotypes. A nested matched case-control study also revealed no significant effect of the CCR5 and CCR2b mutations. Immunologic differences between IDUs and homosexual men may account for the observed lack of effect. Alternatively, difference in transmission route or characteristics of the HIV-1 variants that circulate in IDUs could also explain this phenomenon.

[Opportunistic screening for genital infections with Chlamydia trachomatis among the sexually active population of Amsterdam. Il Over 90% participation and almost 5% prevalence]

OBJECTIVE

To determine in an opportunistic screening programme for Chlamydia trachomatis (CT) the participation and the CT prevalence among the heterosexual population.

METHODS

Heterosexually active men and women, 15-40 years old, who consulted a general practitioner in Amsterdam, the Netherlands, in the period May 1996-April 1997, without symptoms of a sexually transmitted disease, were asked after informed consent had been given to provide a first-voided urine sample and a few sociodemographic data. The urine was investigated for CT by means of a ligase chain reaction. In case of a CT infection, the general practitioner was asked for information on treatment and partner notification.

RESULTS

A total of 3689 persons were eligible for the study of whom 214 (5.8%) refused participation. Men refused more often than women (9.0% and 4.3% respectively). No relation was found with ethnic background or health care insurance (national health cost insurance/private medical insurance). Refusers were somewhat younger than participants (not statistically significant). CT was diagnosed in 4.9% (95% confidence interval (95% CI): 4.1-5.9) of the women and in 4.7% (95% CI: 3.6-6.1) of the men. In women a decreasing trend was seen in the prevalence of CT with an increase in age: from 13.4% in the group 15-19 years old to 2.3% in the group 35-40 years old. Independent of age a higher prevalence was found in Surinam Creole women. In 83% of the CT patients the general practitioner spoke with the patient about partner notification; usually there was one partner.

CONCLUSION

There was a high participation rate (94%) in this opportunistic screening programme in which urine was tested for presence of CT. The CT prevalence in this asymptomatic population was almost 5%, but it was significantly higher in young women and women from Surinam. It is proposed to start such a screening programme in all general practices in Amsterdam.

[Opportunistic screening for genital infections with Chlamydia trachomatis in sexually active population of Amsterdam. II. Cost-effectiveness analysis of screening women]

OBJECTIVE

To estimate the cost effectiveness of Chlamydia trachomatis (CT) screening of young women visiting general practitioners.

DESIGN

Economic model analysis.

METHODS

Data on the health care needs for CT complications were derived from various sources; costing was done using estimated cost prices, charges and the friction cost method; epidemiological data were derived from a pilot study among 22 general practices in Amsterdam, the Netherlands. The analyses were carried out assuming screening with ligase chain reaction test of a urine sample and treatment of identified cases of infection with single-dose azitromycin. The model intervention consisted of screening all heterosexually active women aged 15-19, 15-24, 15-29, or 15-34 years (strategies 1, 2, 3 and 4, respectively). Cost effectiveness was presented in net direct and indirect costs per woman cured and per major outcome averted (pelvic inflammatory disease (PID), chronic pelvic pain, ectopic pregnancy, infertility and pneumonia of newborns).

RESULTS

The first two strategies were cost saving. For the third strategy net costs per woman cured and per major outcome averted were almost 110.- Dutch guilders (DFL) and over DFL 300, respectively. The last strategy costs over DFL 320 per woman cured and over DFL 910 per major outcome averted. The cost effectiveness was sensitive to the assumed probability of progression of CT infection to PID.

CONCLUSION

Universal implementation of the screening programme investigated in Amsterdam for women aged 15-24 years would result in approximately equal savings and costs. Screening of all 15-29-year-old women would require a net investment of DFL 350,000.

[Therapeutic options for HIV infection should lead to increased utilization of HIV tests]

Owing to the recent advances in drug therapy for HIV infected patients, HIV infection is no longer an untreatable condition. The Health Council of the Netherlands therefore considers the advantages of knowing a person's HIV status to outweigh the disadvantages, especially for pregnant women. The restrictive policy with respect to HIV testing should be discontinued.

Evaluation of the World Health Organization staging system for HIV infection and disease in Ethiopia: association between clinical stages and laboratory markers

OBJECTIVE

To study the association between the clinical axis of the World Health Organization (WHO) staging system of HIV infection and disease and laboratory markers in HIV-infected Ethiopians.

DESIGN

Cross-sectional study.

METHODS

Clinical manifestations and stage of HIV-positive individuals participating in a cohort study of HIV infection progression, and of HIV-positive patients hospitalized with suspicion of AIDS, were compared to CD4+ T-cell count and viral load.

RESULTS

Of the 86 HIV-positive participants of the cohort study, 53 (62%), 16 (19%), 16 (19%), and one (1.2%) were in stage 1, 2, 3 and 4, respectively. Minor weight loss (n = 15) and pulmonary tuberculosis (n = 9) were the most commonly diagnosed conditions among the 38 (44%) symptomatic HIV-positive individuals. Although 23 (27%) HIV-positive participants had CD4+ T-cell counts less than 200 x 10(6)/l, only one was in clinical stage 4. Among 79 hospitalized HIV-positive patients, 15 (19%) and 64 (81%) were in stage 3 and 4, respectively. The majority (83.5%) had CD4+ T-cell counts < 200 x 10(6)/l. Individuals at stage 3 had lower CD4+ T-cell counts and higher viral loads when seen in hospital as compared to cohort participants (P = 0.06 and 0.008, respectively). When grouping the two study populations, the median CD4+ T-cell count decreased (337, 262, 225, 126, and 78 x 10(6)/l, P< 0.01), and the median viral load increased (4.08, 3.89, 4.47, 5.65, and 5.65 log10 copies/ml, P < 0.01), with increasing clinical stage of HIV infection (1, 2, 3 cohort, 3 hospital, and 4, respectively). Median CD4+ T-cell counts were remarkably low in HIV-negative participants (749 x 10(6)/l), and in HIV-positive participants at stage 1 and 2 (337 and 262 x 10(6)/l, respectively).

CONCLUSIONS

There was a good correlation between WHO clinical stages and biological markers. CD4+ T-cell counts were low in Ethiopians, particularly during early stages of HIV-1 infection, and preliminary reference values at different stages of HIV-1 infection were determined. In HIV-infected Ethiopians, lymphocyte counts less than 1,000 x 10(6)/l in non-hospitalized individuals, and less than 2,000 x 10(6)/l in hospitalized patients, had high positive predictive value, but low sensitivity, in identifying subjects with low CD4+ T-cell counts (< 200 x 10(6)/l) who would benefit from chemoprophylaxis of opportunistic infections. The on-going longitudinal study will be useful to confirm the prognostic value of the WHO staging system.

[Tinea capitis in primary school age children in southeastern Amsterdam: primarily due to Trichophyton tonsurans]

OBJECTIVE

To establish prevalence and aetiology of tinea capitis in children attending primary school in Amsterdam South-East.

DESIGN

Prevalence survey.

METHODS

The Municipal Health Service Amsterdam, the Netherlands, selected classes of four primary schools in a survey with children clinically suspected of having tinea capitis as well as classes without clinical cases. Per school at least one class with a notified case was included. Written information was provided to all parents; the parents of three children refused participation. After clinical examination by a team of physicians and nursing staff scalp cultures were taken using the brush method from 315 children (aged 4-12 years) in 16 classes.

RESULTS

The clinical diagnosis 'tinea capitis' was established in 25 children, significantly more in boys than in girls (relative risk (RR) = 2.92: 95% confidence interval (95% CI) 1.20-7.11). Of all children 7% had positive cultures, more boys than girls (RR = 3.13: 95% CI: 1.18-8.28). Symptomatic cases (confirmed by culture) amounted to 3.2% of all children. The carrier rate was 3.8%. Trichophyton tonsurans was the most frequently isolated dermatophyte both in symptomatic children and in carriers.

CONCLUSION

In 7% of all children (3.2% with symptoms of tinea capitis, 3.8% without) dermatophytes were cultured from scalp samples, the main aetiologic agent being T. tonsurans.

[Surveillance of AIDS and HIV infections in Amsterdam, 1997]

Data were collected in Amsterdam in 1997 from the aids surveillance, from the HIV surveillance among pregnant women and visitors of a clinic for sexually transmitted diseases (STD), and from two 'alternative' HIV test sites, using various survey systems. The findings were compared with those of previous years. Aids was diagnosed in 1997 in 123 patients, in 194 in 1996. Of the 354 patients in whom aids was diagnosed in 1993-1997 in a hospital recording additional information, 113 patients (32%) only learned that they had an HIV infection when aids was diagnosed in them. In 1997, out of 225 pregnant women with an increased risk of HIV infection, 10 were HIV seropositive (4.4%); in 1996, this proportion was 3/285 (1.1%). Among those attending STD clinics, HIV infection was observed approximately as frequently as in earlier years: about 1% of heterosexual men and women.

Seroconversion for human herpesvirus 8 during HIV infection is highly predictive of Kaposi's sarcoma

BACKGROUND

The finding of antibodies against human herpesvirus 8 (HHV-8) is associated with the occurrence of Kaposi's sarcoma in persons infected with HIV. However, the predictive value of HHV-8 antibodies for Kaposi's sarcoma in HIV infection is unknown.

METHODS

The Amsterdam Cohort Studies on HIV infection and AIDS started in 1984 for homosexual men and in 1985 for injecting drug users. Serum samples from 1459 homosexual men and 1167 drug users were tested for antibodies to recombinant HHV-8 lytic-phase capsid (ORF65) antigen and latent-phase nuclear (ORF73) antigen. Individuals were retrospectively identified as HHV-8-positive or HHV-8-negative at enrolment or HHV-8 seroconverter during the study. Kaposi's sarcoma-free survival time was compared between HIV-infected men who were positive for HHV-8 at enrolment and those who later seroconverted for HHV-8. Hazard ratios were estimated for Kaposi's sarcoma, lymphoma, and opportunistic infection according to the HHV-8 serostatus.

RESULTS

The incidence of HHV-8 seroconversion among drugs users was 0.7 per 100 person-years based on 31 seroconversions, whereas an incidence of 3.6 was found among homosexual men based on 215 seroconversions. The hazard ratio for Kaposi's sarcoma was 3.15 (95% CI: 1.89-5.25) in HIV-infected individuals if HHV-8 antibodies were present either at enrolment or at HIV seroconversion. In HIV-infected persons who later seroconverted to HHV-8, Kaposi's sarcoma developed more rapidly: hazard ratio of 5.04 (95% CI: 2.94-8.64), an additional risk of 1.60 (95% CI: 1.01-2.53; P = 0.04). Time-dependent adjustment for CD4+ cell count and HIV RNA had no impact on the additional risk, although the CD4+ cell count was an independent risk factor for Kaposi's sarcoma. HHV-8 infection did not increase the risk of AIDS-related lymphoma or opportunistic infections.

CONCLUSIONS

The incidence of HHV-8 infection is higher in homosexual men than in drug users. The presence of HHV-8 antibodies in HIV-infected persons increases the risk of Kaposi's sarcoma. Among HIV-infected persons, those who subsequently seroconvert for HHV-8 are at highest risk. These results strongly confirm the causal role of HHV-8 in Kaposi's sarcoma and emphasize the clinical relevance of HHV-8 seroconversion before and after the HIV infection.

Role of CCR2 genotype in the clinical course of syncytium-inducing (SI) or non-SI human immunodeficiency virus type 1 infection and in the time to conversion to SI virus variants

The effect of a valine to isoleucine switch in the CCR2 first transmembrane domain (CCR2 64I) on the clinical course of human immunodeficiency virus type 1 (HIV-1) infection was analyzed in relation to the presence or absence of syncytium-inducing (SI) HIV-1 variants. Compared with persons with a wild-type genotype for CCR2 and CCR5, subjects with a CCR2-64I/+ or 64I/64I (but CCR5 wild-type homozygous genotype) had significantly delayed disease progression (relative hazard, 0.66; 95% confidence interval, 0.44-0.99) with a 1. 5-fold slower CD4 T lymphocyte decline and a 1.2-fold lower RNA virus load. The delay in disease progression was more pronounced when only non-SI (NSI) HIV-1 variants were present and was not observed after conversion to SI HIV-1 in CCR2-64I/+ persons. In CCR2-64I/+ subjects, a higher conversion rate to and a higher prevalence of SI HIV-1 was observed. These findings suggest that the mechanism of action of the CCR2 polymorphism is mediated via CCR5-restricted NSI HIV-1 variants.

Incidence and risk factors of diarrhoea in Dutch travellers: consequences for priorities in pre-travel health advice

A cohort of 743 Dutch short-term travellers (1-6 weeks) to various (sub)tropical areas was studied to assess incidences of travellers' diarrhoea (TD) and risk factors to guide prevention policies. The occurrence of TD was ascertained retrospectively by questionnaire; independent risk factors were identified by logistic regression analysis. The overall attack rate (AR, 95% CI) of TD was 52% (49-56); 11% (9-14) reported two or more episodes. The overall incidence rate (IR) per 100 person weeks of travel (pwt) (95% CI) was 22 (20-24). IRs were highest for travellers to the Middle East (48, 33-71), lowest for South-east Asia (17, 15-20) and East Africa (18, 14-24) and intermediate for South America and West Africa (both 26, 19-36), Central America (29, 23-37) and the Indian subcontinent (32, 26-39). Compared to first episodes of TD, subsequent episodes were of longer duration and more frequently accompanied by faecal blood loss, abdominal cramps or systemic symptoms. After adjustment for travel duration and destination, independent risk factors (OR, 95% CI) for TD were recent treatment for gastrointestinal (GI) disorders (4.6, 1.2-17.2), history of GI surgery (3.9, 1.4-11.1) and, possibly, current use of medication reducing gastric acidity (6.9, 0.7-67.4). The risk was reduced for extensive travel experience (0.4, 0.3-0.7) and organized travel (0.7, 0.5-0.9). Regarding prevention and/or antibiotic self-treatment of TD, priority should be given to travellers who may suffer major health or other consequences from TD and to those with pre-existing GI disorders, particularly when visiting a high or intermediate-risk area on individual journeys with limited travel experience.

Body mass index course in asymptomatic HIV-infected homosexual men and the predictive value of a decrease of body mass index for progression to AIDS

Weight loss is a common characteristic of advanced stages of HIV infection. Weight changes during the asymptomatic stage of HIV infection have not been well documented and the possible predictive value of early weight loss for progression to AIDS is unknown. In 122 HIV seroconverters, the natural course of body mass index (BMI) following seroconversion was studied. No BMI decline was seen immediately following seroconversion. In the 56 AIDS cases, however, a steep BMI decline of 1.14 kg/m2 occurred 6 months before AIDS. This BMI decline was more pronounced in those with low CD4+ T cell counts (<100 x 10(6)/L) at the time of AIDS diagnosis (1.8 kg/m2). The relative hazard for progression to AIDS of a BMI decline of 1.14 kg/m2 per 6 months was 3.1, which remained similar after adjustment for CD4 count and p24 antigenemia. We conclude that the course of BMI in HIV-1 infection is biphasic: a relatively stable period is followed by a rapid decline in the 6 months preceding onset of AIDS. Furthermore, we found that this steep BMI decline was associated with faster progression to AIDS.

[Accidental exposure to blood and the risk of transmission of virus infections for various occupational groups in Amsterdam, 1986-1996]

Since 1986 the number of parenteral exposures to potentially infectious blood reported to the Amsterdam Public Health Service increases every year. The number of needlestick accidents increased significantly from 64 in 1986 to 166 in 1996 whereas the number of other exposures decreased from 59 to 44 in these years. The increase was mainly seen in nonhospital based (para)medics. A possible explanation of this increase is greater awareness of the potential infection risk with HIV, hepatitis B or C virus leading to a tendency to report more readily. This assumption is in contradiction with results of studies in hospital-based personnel where a decrease is observed as a result of educational programmes. Other explanations are a higher frequency of use of sharp instruments and (or) an increase in the workload. Out of a total of 1886 needlestick accidents in 1986-1996 one woman became HIV positive; she was deliberately infected by her ex-partner who injected her with blood of an AIDS patient, and one person contracted an hepatitis C virus infection: a policeman wounded by a needle used by a drug addict.

In vivo delayed-type hypersensitivity skin test anergy in human immunodeficiency virus type 1 infection is associated with T cell nonresponsiveness in vitro

In a cross-sectional study, the prevalence of delayed-type hypersensitivity skin test anergy (DTHA) was examined in 136 asymptomatic human immunodeficiency virus-infected participants in relation to immunologic and virologic parameters. DTHA was assessed with a multitest cell-mediated immunity skin test. Of the 136 participants, with a mean CD4 T cell count of 335 x 10(6)/L, 25 were anergic (18.4%). In the stepwise forward multivariate logistic regression models, after adjustment for CD4 T cell counts, depending on whether it was analyzed continuously or after dichotomization (20th percentile), both T cell reactivity to CD2 plus CD28 antibodies or to CD3 antibodies were the most predictive markers of DTHA (odds ratio, 0.80; 95% confidence interval, 0.67-0.94; and odds ratio, 2.97; 95% confidence interval, 1.1-8.3, respectively). This study shows a strong correlation between the decreased T cell responses in vitro and DTHA. Therefore, next to DTHA testing, T cell function assays may be useful to test immune reconstitution observed during antiretroviral treatment.

Methods for estimating HIV prevalence: A comparison of extrapolation from surveys on infection rate and risk behaviour with back-calculation for the Netherlands

OBJECTIVES

To compare HIV prevalence estimates (total number infected) by using extrapolation from surveys on infection rate and risk behaviour (EIR) in specific segments of the population and back-calculation (BC) on reported AIDS cases. To discuss potential sources of bias and error, and to identify areas for improvement of the methodology.

DESIGN

Systematic comparison and epidemiological assessment of data input, underlying assumptions, and output.

METHODS

Low, possibly unbiased and high estimates of HIV prevalence as of January 1996 for homo/bisexual men, injecting drug users. heterosexual men and women with multiple partners, and blood transfusion recipients and haemophiliacs were derived from surveys and continuous data collections on HIV infection rate and risk behaviour in the Netherlands between 1992 and 1996. These were compared with estimates (point and 95 % CI) by empirical Bayesian BC on AIDS cases 1982-1995.

RESULTS AND CONCLUSIONS

The estimate of HIV prevalence by EIR was 13,806 with low and high estimates of 9619 and 17,700, respectively. The HIV prevalence estimate by BC was 8812 (95% CI: 7759-9867). The available data from EIR are too limited for accurate estimates of HIV prevalence. EIR estimates could be improved considerably with more precise data on prevalence of risk behaviours and HIV prevalence rate for homosexual men. More confidence can be put in the BC estimates, but these could be underestimates because of the age effect on incubation time, pre-AIDS treatment and relapse of risk behaviour. BC estimates could be improved by a better representation of the incubation time distribution (including the effect of age there-upon), better data on the effectiveness and uptake of pre-AIDS antiretroviral treatment and prophylaxis of opportunistic infections, and on the level of underreporting.

Low T-cell responses to CD3 plus CD28 monoclonal antibodies are predictive of development of AIDS

OBJECTIVE

Decreased T-cell reactivity in vitro is strongly associated with progression to AIDS and low CD4+ T-cell numbers. Low T-cell responses in vitro induced by CD3 monoclonal antibody (mAb) are predictive for progression to AIDS independent of low CD4+ T-cell counts and high HIV-1 RNA levels. We developed a whole-blood lymphocyte culture system in which T cells were stimulated by a combination of CD3 and CD28 mAb. Combined stimulation of CD28, a costimulatory molecule, and CD3 considerably enhances T-cell responses in vitro and reduces variation coefficients, which may increase the prognostic power of T-cell responses.

DESIGN

A prospective study of HIV-1-infected homosexual men followed for 35 months.

METHODS

The predictive value of low T-cell responses to CD3 plus CD28 mAb relative to low CD4+ T-cell counts, high HIV-1 RNA levels and the presence of syncytium-inducing (SI) HIV-1 variants was evaluated longitudinally in 202 HIV-1-infected homosexual men followed for 35 months.

RESULTS

In multivariate analysis, decreased T-cell responses at baseline were predictive of development of AIDS, independent of low CD4+ T-cell numbers and high HIV-1 RNA levels. In a time-dependent model, HIV-1 RNA levels lost their predictive value, whereas low T-cell responses, low CD4+ T-cell numbers and the presence of SI HIV-1 variants independently predicted AIDS.

CONCLUSIONS

These data demonstrate that combined use of virological and immunological markers may be useful in monitoring disease progression and response to antiretroviral therapy.

[Annual epidemics of hepatitis A in four large cities related to holiday travel among immigrant children]

OBJECTIVE

Analysis of the transmission pattern of hepatitis A in relation to ethnicity and travel behaviour in Amsterdam. Utrecht, Rotterdam and The Hague.

DESIGN

Descriptive study of notified cases.

SETTING

Municipal Health Services of the four major cities in the Netherlands.

METHOD

Notification data of hepatitis A in Amsterdam, Utrecht, Rotterdam and The Hague were analysed over the period 1992-1995. Cases were analysed according to age (0-19 years or > 19 years), whether or not they travelled abroad in the period of six weeks before the onset of the first symptoms of disease, and endemicity of hepatitis A in the country of ethnic origin.

RESULTS

The strong increase of hepatitis A after the summer holidays could be divided into several smaller epidemics starting with an epidemic among children of Moroccan and Turkish descent who had spent the summer holidays in these countries, among children of the same ethnic background who had not travelled abroad, followed by epidemics among non-travelling children and adults of mainly Dutch descent, respectively. A strong correlation was found in Amsterdam between the incidence in the former two groups and the latter two groups (Pearsons r = 0.68; p = 0.004).

CONCLUSION

Children who spent the summer holidays in a hepatitis A endemic country, particularly Morocco and Turkey, appeared to be the main importers of hepatitis A in the four major cities. Active immunization of all children born in the Netherlands of Moroccan and Turkish descent is the most preferable intervention.

The incubation period to AIDS in injecting drug users estimated from prevalent cohort data, accounting for death prior to an AIDS diagnosis

OBJECTIVE

To estimate the incubation-period distribution (time from seroconversion to AIDS) accounting for death before an AIDS diagnosis (DBAD) in a cohort of injecting drug users (IDU) in Amsterdam, The Netherlands and to compare these estimates with those previously obtained from a contemporaneous study of homosexual and bisexual men in Amsterdam carried out using the same facilities.

DESIGN

Participants in a cohort study begun in Amsterdam at the end of 1985 have scheduled follow-up visits every 4 months. All participants of Dutch nationality and who had two or more follow-up visits before January 1996 from which CD4 measurements were available were included in this study. Data concerning AIDS diagnosis and death were verified through review of national and municipal registries.

METHODS

Because time of seroconversion was unknown for study participants and because IDU are at substantial risk for DBAD, we used a Markov model with CD4-based stages that allows for DBAD. The parameters in this model were estimated using the method of maximum likelihood and confidence intervals were calculated using bootstrap methods.

RESULTS

A total of 173 IDU (134 seroprevalent, 39 seroincident) made 1829 visits. Nearly 10% of the visits were non-consecutive. Forty-five IDU developed AIDS and 25 died without an AIDS diagnosis. We estimated that 24% [95% confidence interval (CI), 17-25%] of IDU die before an AIDS diagnosis. As a result, the median time from seroconversion to AIDS (10.5 years; 95% CI, 9.1-10.7 years) is considerably longer than the median time from seroconversion to death (8.3 years; 95% CI, 7.9-8.5 years). Conditional on survival to an AIDS diagnosis, the median time to AIDS is 8.2 years (95% CI, 7.7-8.7 years). The median survival time after a diagnosis of AIDS is estimated to be 1.0 years.

CONCLUSION

The high occurrence of DBAD in IDU has a considerable influence on estimates of the incubation-period distribution. Progression from seroconversion to death was faster in the IDU cohort than in a cohort of homosexual men in Amsterdam (median, 8.3 years and 9.6 years, respectively). However, progression to AIDS conditional on survival to an AIDS diagnosis seems to be similar in both the IDU cohort and in the cohort of homosexual men (median, 8.2 years and 8.3 years, respectively).

Evaluation of the Eiken latex agglutination test for anti-Toxoplasma antibodies and seroprevalence of Toxoplasma infection among factory workers in Addis Ababa, Ethiopia

Sera from 170 factory workers aged 18-45 years enrolled in a pilot study of human immunodeficiency virus 1 (HIV-1) infection in Addis Ababa, Ethiopia, were screened for anti-Toxoplasma immunoglobulin G antibodies by the Sabin-Feldman test (reference standard) and the Eiken latex agglutination test (under evaluation for use in developing countries). Based on the Sabin-Feldman test, the prevalence of anti-Toxoplasma antibodies was 80.0% (95% confidence interval 73.9-86.1%). The sensitivity and specificity of the Eiken latex agglutination test were 96.3% and 97.1%, respectively, showing its validity for the detection of anti-Toxoplasma antibodies. The prevalence of antibodies did not differ between individuals infected and uninfected with HIV-1 (74.2% versus 83.3%, P > 0.05). However, antibody titres were higher in HIV-infected persons than in those who were uninfected (P < 0.001). Based on these findings, we expect that toxoplasmic encephalitis will be a common opportunistic infection among HIV-infected Ethiopians, and chemoprophylaxis with co-trimoxazole may be beneficial to those with low CD4+ T cell counts. The prognostic significance of high titres of anti-Toxoplasma antibodies remains to be established among Ethiopian HIV-infected individuals.