Biomedical subjects

Ahmadou Alioum

Publications and source records attributed to Ahmadou Alioum.

11 recordsLinked to original sources

PubMed2007

Estimating incidence of HIV infection in childbearing age African women using serial prevalence data from antenatal clinics.

Ades and Medley provided the first flexible method for estimating age- and time-specific HIV incidence using HIV prevalence data collected among pregnant women and adjusting for the effect of differential selection between infected and uninfected women. This paper extends the approach proposed by these authors. We used a parametric model that allows the relative inclusion rate to depend on both age, calendar time, and duration of HIV infection. We developed a two dimensional penalized log-likelihood approach for estimating time- and age-specific incidence using a binomial likelihood function and a quadratic roughness penalty which allows smoothing over both age and time. Identifiability of the model parameters and effect of sample size are studied through simulations. The method is illustrated using prenatal HIV testing data recorded from 1995 to 2002 in Abidjan, Côte d'Ivoire, to estimate the HIV annual incidence rate among women aged 12-40 year old, from the beginning of the epidemic to 2002. We show that estimated incidence rates are highly dependent on hypotheses made to model the relative inclusion rate. Despite this dependency, the application of the method leads to new and accurate findings on HIV incidence qualitative features in Abidjan. We highlight the relevance of such a method in monitoring the dynamics of HIV epidemic in Africa which is essential for planning vaccine trials and future treatment needs, and for assessment of prevention policy.

Adolescent↗

PubMed2006

Decrease of human immunodeficiency virus prevalence in antenatal clinics in Abidjan, Côte d'Ivoire, 1995-2002.

Antenatal HIV seroprevalence surveys are important tools to understand the extent of the HIV epidemic in Africa. The main objective is to describe HIV prevalence trends from 1995-2002 in pregnant women consulting antenatal clinics in Abidjan, Côte d'Ivoire. We proposed HIV test to pregnant women consulting antenatal clinics in Abidjan from 1995-2002 in a programme of prevention of mother-to-child transmission of HIV. Yearly prevalence was estimated. Overall, 36,442 women were tested. Prevalence decreased from 14-15% in 1995-96 to 11% in 2002. The prevalence among 18-22-year-old women dropped from 15% in 1995 to 8% in 2002, while for older women it increased slightly, or remained stable from 1995-1999 and decreased thereafter. HIV prevalence among women consulting antenatal clinics has been decreasing overall. This is the first such report among pregnant women in Abidjan, probably the result of different phenomena: ageing of the epidemic and behaviour changes (disease awareness and prevention campaigns).

AIDS Serodiagnosis↗

PubMed2005

Biases in observational studies of the effect of prenatal treatment for congenital toxoplasmosis.

The paper reviews methodological difficulties that arise when using observational studies to evaluate the effect of prenatal screening and treatment. The principle of each difficulty is described and then illustrated by a clinical example of toxoplasmosis in pregnancy and its consequences. Methods to deal with these difficulties are described. Given the limitations of existing observational studies and lack of randomised controlled trials, a systematic review of cohort studies offers the best approach for exploring potential biases.

Adult↗

PubMed2005

Use of a Bayesian approach to decide when to stop a therapeutic trial: the case of a chemoprophylaxis trial in human immunodeficiency virus infection.

From 1996 to 1998, a phase III, placebo-controlled, therapeutic trial was conducted in Abidjan, Ivory Coast, to assess the efficacy of cotrimoxazole prophylaxis in reducing severe morbidity in adults at early stages of human immunodeficiency virus infection. The authors used the real data from this trial to simulate three Bayesian interim analyses. Three prior distributions were considered: a noninformative one, a skeptical one, and one based on external information. The posterior distribution was calculated by using directed acyclic graphs and Gibbs sampling. This Bayesian approach showed different results according to the prior distribution chosen. Although use of the noninformative prior would have led to stopping the trial at the same time that the frequentist approach would have, the skeptical prior would have led to continuing it, and the prior based on external data would have led to stopping it 1 year earlier.

Anti-Infective Agents↗

PubMed2005

The disablement process: factors associated with progression of disability and recovery in French elderly people.

PURPOSE: To study the factors associated with progression, recovery and death from different grades of disability in elderly people. METHOD: The sample included 3198 participants of the PAQUID ('Personnes Agées QUID') cohort, aged 65 and over and community-dwellers at baseline. Subjects were re-interviewed 1, 3, 5, 8 and 10 years after baseline. A five-state Markov model was used to estimate transition intensities between four grades of disability and toward death. We used a hierarchic scale of disability, which combines basic and instrumental activities of daily living and mobility. Several explanatory variables were investigated: medical, personal and environmental factors. RESULTS: The factors associated with progression and/or no recovery of disability were cardiovascular diseases, stroke and diabetes, low cognition, visual impairment and dyspnoea (for pathologies and impairments), older age, female gender, low educational level (for risk factors), depression (for intra-individual factor) and being married, recent hospitalization and number of drugs (for extra-individual factors). Older age, male gender, tobacco consumption and living in an urban area were associated with mortality. CONCLUSIONS: These findings confirm the independent contribution of each group of variables in the disablement process and stress their different impact on progression of disability or on recovery from different grades of disability.

Age Factors↗

PubMed2004

The contribution of dementia to the disablement process and modifying factors.

The objective of this study was to examine the impact of dementia on disability progression and mortality, and to analyze the modifying effect of risk factors and extra-individual factors. A sample of 3,403 participants in the PAQUID study was followed for 10 years. Disability was assessed on a 4-grade scale: no disability, disabled only on the Rosow-Breslau scale, disabled on the Rosow-Breslau scale and on instrumental activities of daily living (IADL) scales, and disabled on the Rosow-Breslau, IADL and activities of daily living (ADL) scales. A Markov model was used to estimate the effect of explanatory variables on disability and mortality. Controlling for age, gender, education, place of residence, medical care and informal support, dementia had a strong significant effect on progression to IADL and then to ADL disability. Dementia did not increase the risk of death, once disability was taken into account, except from the lowest disability grade.

Aged↗

PubMed2003

Estimating the efficacy of interventions to prevent mother-to-child transmission of human immunodeficiency virus in breastfeeding populations: comparing statistical methods.

Postnatal transmission of human immunodeficiency virus infection through breastfeeding complicates evaluating the efficacy of interventions aimed to reduce mother-to-child transmission risk. Results from trials in Africa evaluating either peripartum antiretroviral therapy or refraining from breastfeeding show an estimated long-term efficacy at 15-24 months of age between 25 and 50 percent. Differences in statistical methods, duration of follow-up, and age at weaning hinder direct comparison between trials. The authors recently outlined theoretically preferred statistical methods for evaluating interventions aimed to reduce risk of mother-to-child transmission of human immunodeficiency virus. When multiple test results and/or supplementary information is available, the more sophisticated methods account for the fact that exact age at infection is unknown, that risk for infection ends at weaning, or that censoring due to death may be informative. The authors apply these methods to four scenarios, using data from four randomized trials carried out in Africa between 1995 and 2000. The authors' findings suggest that, to estimate the cumulative proportion infected at age 6 weeks, a standard Kaplan-Meier approach is likely to give valid results. For estimation of this proportion at age 18 months, more sophisticated methods, such as the extension of the Kaplan-Meier procedure to interval-censored data and competing risks, would be preferred.

Adult↗

PubMed2003

Postnatal transmission of HIV-1 after a maternal short-course zidovudine peripartum regimen in West Africa.

BACKGROUND: To assess the postnatal transmission (PT) risk of HIV-1 after a maternal short-course zidovudine regimen in a breastfeeding population. METHODS: Data were pooled from two trials: ANRS 049a DITRAME (Abidjan, Côte d'Ivoire and Bobo-Dioulasso, Burkina-Faso) and RETROCI (Abidjan). Consenting HIV-1 seropositive women were randomized at 36-38 weeks' gestation between September 1995 and February 1998, to receive oral zidovudine or placebo: one tablet twice daily until delivery, and in DITRAME only, for 7 more days. A PT case was infection in a child with a negative HIV-1 PCR at age >/= 30 days who later became infected as defined by a positive HIV-1 PCR, or if aged >/= 15 months, a positive HIV serology. Cumulative risks (CR) of PT were computed using a competing risk approach with weaning as a competing event. FINDINGS: At age 24 months, CR for PT were similar in the zidovudine (9.8%, n = 254) and placebo groups (9.1%, n = 225). In a multivariate model of PT risk factors, the treatment effect was not significant, maternal CD4 cell count < 500 x 10(6)/l at entry tripled the hazard compared to women with CD4 cell counts >/= 500 x 10(6)/l [hazard ratio (HR), 3.14; 95% confidence interval (CI), 1.31-7.49] as well as an increased maternal plasma viral load at entry (HR, 2.65 for 1 log(10) increase; CI, 1.75-4.00). INTERPRETATION: PT occurred at a similar rate between arms and therefore reduced the long-term overall efficacy of this peripartum zidovudine regimen at age 24 months. The higher risk of PT among women with low CD4 cell count emphasizes the importance of identifying interventions to prevent PT for these women.

Adult↗

PubMed2002

Twenty-four month efficacy of a maternal short-course zidovudine regimen to prevent mother-to-child transmission of HIV-1 in West Africa.

OBJECTIVE: To assess the 24 month efficacy of a maternal short-course zidovudine regimen to prevent mother-to-child transmission (MTCT) of HIV-1 in a breastfeeding population in West Africa. METHODS: Data were pooled from two clinical trials: DITRAME-ANRS049a conducted in Abidjan, Côte d'Ivoire and Bobo-Dioulasso, Burkina-Faso and RETRO-CI, conducted in Abidjan. Between September 1995 and February 1998, consenting HIV-1-seropositive women were randomly assigned to receive zidovudine (300 mg) or placebo: one tablet twice daily from 36-38 weeks' gestation until delivery, then in DITRAME only, for 7 more days. Paediatric HIV-1 infection was defined as a positive HIV-1 polymerase chain reaction, or if aged > or =15 months, a positive HIV-1 serology. Cumulative risks (CR) of infection were estimated using a competing risk approach with weaning as a competing event. RESULTS: Among 662 live-born children, 641 had at least one HIV-1 test. All but 12 children were breastfed. At 24 months, overall CR of MTCT were 0.225 in the zidovudine and 0.302 in the placebo group, a 26% significant reduction. Among children born to women with CD4 cell counts < 500/ml at enrollment, CR of MTCT were similar, 0.396 in the zidovudine and 0.413 in the placebo group. Among children born to women with CD4 cell counts > or =500/ml, CR of MTCT were 0.091 in the zidovudine and 0.220 in the placebo group, a significant 59% reduction. CONCLUSION: A maternal short-course zidovudine regimen reduces MTCT of HIV-1 at age 24 months, despite prolonged breastfeeding. However, efficacy was observed only among women with CD4 cell counts > or =500/ml. New interventions should be considered to prevent MTCT, especially for African women with advanced HIV-1 immunodeficiency.

Africa, Western↗

PubMed2002

Predictors of virological rebound in HIV-1-infected patients initiating a protease inhibitor-containing regimen.

OBJECTIVE: To study the predictors of virological rebound in patients having early virological response to protease inhibitor (PI)-containing regimen. DESIGN AND METHODS: APROCO cohort study prospectively enrolled 1283 HIV-infected patients starting a PI-containing regimen in 1997-1999. Adherence to therapy was measured with self-administered questionnaires after 4 months of therapy (M4). Virological rebound was defined as a viral load (VL) > 500 copies/ml in patients having early virological response, defined as a VL < 500 copies/ml at M4. Predictors of time to virological rebound were studied with multivariate proportional hazards model. RESULTS: During a median follow-up of 20 months, virological rebound was observed in 32% of the 830 patients with early virological response. Virological rebound was more frequent when patients had received previous antiretroviral treatment [adjusted hazards ratio (HR) = 2.4; P < 0.0001], were younger (HR = 1.4 per each 10 years younger; P < 0.0001), had baseline CD4 cell count < 500 x 106/l (HR = 2.3; P < 0.001), had higher baseline VL (HR = 1.4 per each log10 copies/ml higher; P < 0.001), reported low adherence to therapy at M4 (HR = 2.1; P < 0.001) or had stopped PI at M4 (HR = 1.7; P = 0.04). CONCLUSION: Initiation of treatment at a stage of preserved immunity is associated with a more durable virological response under protease inhibitor. Every effort should be made to monitor and strengthen adherence to therapy, even in patients having early virological response.

Adult↗

PubMedDate not supplied

Impact of the Salmonella status of market-age pigs and the pre-slaughter process on Salmonella caecal contamination at slaughter.

The aim of this study was to evaluate the impact of the pre-slaughter process on Salmonella caecal contamination of pigs at slaughter. An observational study was carried out in 2001 on 101 conventional farrow-to-finish pig farms. On each farm, one batch of contemporary pigs was followed from the end of the fattening period until slaughter. The Salmonella bacteriological status of the batches was assessed by environmental samples of faecal material. The serological Salmonella status was obtained on 30 individually identified market-age pigs using an indirect ELISA test. At the slaughterhouse, 25 g of caecal contents were taken from 10 of the identified pigs. Faecal and caecal material were analysed according to a classical bacteriological method. A questionnaire was designed to obtain information about the type of feeding during the fattening period (dry versus wet), the duration of fasting on the farm before leaving for the slaughterhouse, the duration of transport between the farm and the slaughterhouse, the holding time in lairage at the slaughterhouse and loading and unloading conditions on the farm and at the slaughterhouse. To assess the relationships between these factors and the Salmonella caecal status of the pigs and the batches, two logistic models were fitted at the individual and at the batch level, respectively. The first analysis was performed using a random effects logistic regression model. The second analysis was based on a cumulative logit model with a positive caecal rate classified into three classes as the outcome variable. The results showed that the Salmonella status of market-age pigs assessed on the farm either by serological or bacteriological examinations and the time spent in lairage before slaughtering played a crucial role on caecal contamination. In the light of these results, actions should be considered both on the farm and at the slaughterhouse to decrease the risk of Salmonella contamination of the caecal contents.

Abattoirs↗