Biomedical subjects

Stéphane Ranque

Publications and source records attributed to Stéphane Ranque.

7 recordsLinked to original sources

PubMed2006

Space-time clustering of childhood malaria at the household level: a dynamic cohort in a Mali village.

BACKGROUND: Spatial and temporal heterogeneities in the risk of malaria have led the WHO to recommend fine-scale stratification of the epidemiological situation, making it possible to set up actions and clinical or basic researches targeting high-risk zones. Before initiating such studies it is necessary to define local patterns of malaria transmission and infection (in time and in space) in order to facilitate selection of the appropriate study population and the intervention allocation. The aim of this study was to identify, spatially and temporally, high-risk zones of malaria, at the household level (resolution of 1 to 3 m). METHODS: This study took place in a Malian village with hyperendemic seasonal transmission as part of Mali-Tulane Tropical Medicine Research Center (NIAID/NIH). The study design was a dynamic cohort (22 surveys, from June 1996 to June 2001) on about 1300 children (<12 years) distributed between 173 households localized by GPS. We used the computed parasitological data to analyzed levels of Plasmodium falciparum, P. malariae and P. ovale infection and P. falciparum gametocyte carriage by means of time series and Kulldorff's scan statistic for space-time cluster detection. RESULTS: The time series analysis determined that malaria parasitemia (primarily P. falciparum) was persistently present throughout the population with the expected seasonal variability pattern and a downward temporal trend. We identified six high-risk clusters of P. falciparum infection, some of which persisted despite an overall tendency towards a decrease in risk. The first high-risk cluster of P. falciparum infection (rate ratio = 14.161) was detected from September 1996 to October 1996, in the north of the village. CONCLUSION: This study showed that, although infection proportions tended to decrease, high-risk zones persisted in the village particularly near temporal backwaters. Analysis of this heterogeneity at the household scale by GIS methods lead to target preventive actions more accurately on the high-risk zones identified. This mapping of malaria risk makes it possible to orient control programs, treating the high-risk zones identified as a matter of priority, and to improve the planning of intervention trials or research studies on malaria.

Animals↗

PubMed2006

Alleles 308A and 238A in the tumor necrosis factor alpha gene promoter do not increase the risk of severe malaria in children with Plasmodium falciparum infection in Mali.

The hypothesis that tumor necrosis factor (TNF) aggravates malaria in children is supported by observations that TNF polymorphisms and high TNF levels have been associated with cerebral malaria. Nevertheless, severe malaria was not associated with polymorphisms located at positions -308A and -238A in the TNF alpha gene promoter or with a high TNF level in plasma in children from Bamako, Mali.

Alleles↗

PubMed2006

Timely diagnosis of disseminated toxoplasmosis by sputum examination.

The diagnosis of disseminated toxoplasmosis in a 14-year-old allogeneic bone marrow recipient with graft-versus-host disease was determined by the detection of Toxoplasma gondii tachyzoites in sputum smears. Sputum analysis is a valuable alternative in the clinical assessment of pulmonary toxoplasmosis, especially when conventional invasive techniques are not practicable.

Adolescent↗

PubMed2005

Oblique decision trees for spatial pattern detection: optimal algorithm and application to malaria risk.

BACKGROUND: In order to detect potential disease clusters where a putative source cannot be specified, classical procedures scan the geographical area with circular windows through a specified grid imposed to the map. However, the choice of the windows' shapes, sizes and centers is critical and different choices may not provide exactly the same results. The aim of our work was to use an Oblique Decision Tree model (ODT) which provides potential clusters without pre-specifying shapes, sizes or centers. For this purpose, we have developed an ODT-algorithm to find an oblique partition of the space defined by the geographic coordinates. METHODS: ODT is based on the classification and regression tree (CART). As CART finds out rectangular partitions of the covariate space, ODT provides oblique partitions maximizing the interclass variance of the independent variable. Since it is a NP-Hard problem in RN, classical ODT-algorithms use evolutionary procedures or heuristics. We have developed an optimal ODT-algorithm in R2, based on the directions defined by each couple of point locations. This partition provided potential clusters which can be tested with Monte-Carlo inference. We applied the ODT-model to a dataset in order to identify potential high risk clusters of malaria in a village in Western Africa during the dry season. The ODT results were compared with those of the Kulldorff' s SaTScan. RESULTS: The ODT procedure provided four classes of risk of infection. In the first high risk class 60%, 95% confidence interval (CI95%) [52.22-67.55], of the children was infected. Monte-Carlo inference showed that the spatial pattern issued from the ODT-model was significant (p < 0.0001). Satscan results yielded one significant cluster where the risk of disease was high with an infectious rate of 54.21%, CI95% [47.51-60.75]. Obviously, his center was located within the first high risk ODT class. Both procedures provided similar results identifying a high risk cluster in the western part of the village where a mosquito breeding point was located. CONCLUSION: ODT-models improve the classical scanning procedures by detecting potential disease clusters independently of any specification of the shapes, sizes or centers of the clusters.

Africa, Western↗

PubMed2005

Familial aggregation of cerebral malaria and severe malarial anemia.

BACKGROUND: The predominant manifestations of severe malaria in African children are cerebral malaria (CM) and severe malarial anemia (SMA). As a first step toward a family-based approach to identify the environmental and genetic pathways that contribute to severe malaria, we tested whether it aggregates within families. METHODS: Family history of severe malaria was explored during face-to-face interviews with parents. Logistic regression was used to determine whether CM and SMA aggregate within individuals and within families. The pattern of familial aggregation was then expressed as familial odds ratios that were adjusted for relevant risk factors. RESULTS: This study was of 2811 inhabitants of Bamako, Mali, clustered in 407 nuclear families. The probands were 136 children with severe malaria and 271 healthy children from the community. Within-person association of CM and SMA was significant (odds ratio, 6.15 [95% confidence interval (CI), 2.62-14.41]). Over a lifetime, with each additional affected relative, the odds of a person contracting CM increased by 1.98 times (95% CI, 1.59-2.45), and the odds of having SMA increased by 1.91 times (95% CI, 1.05-3.47). Over a lifetime, for a child whose sibling had a history of CM, the odds of having CM were 2.49 times greater (95% CI, 1.51-4.10) than the odds for a child whose sibling had no such history; for a child whose sibling had a history of SMA, the odds of having SMA were 4.92 times greater (95% CI, 1.21-19.9) than the odds for a child whose sibling had no such history. CONCLUSION: Our data suggest strong familial aggregation of CM and SMA.

Adolescent↗

PubMed2004

Risk factors for severe malaria in Bamako, Mali: a matched case-control study.

The aim of this case-control study was to identify epidemiological risk factors for severe malaria among children living in Bamako, a malaria-endemic area. For this, 260 healthy community controls were matched to 130 patients with severe malaria. Conditional multiple logistic regression analysis indicated that all examined independent factors associated with severe malaria are directly related to characteristics of the child's mother, with the exception of the child's own yellow fever vaccination history (odds ratio (OR): 1.93, 95% confidence intervals (CI(95%)) [1.10-3.37]). The following characteristics were all associated with a decreased risk of severe malaria in the child: maternal education (OR: 0.52, CI(95%) [0.31-0.86]), the mother's adequate knowledge about malaria (OR: 0.46, 95% CI(95%) [0.25-0.86]), her use of mosquito bed nets (OR: 0.53, CI(95%) [0.30-0.92]) and breast-feeding for at least 2 years (OR: 0.57, CI(95%) [0.33-0.94]). Conversely, chronic maternal disease (OR: ?3.16, CI(95%) [1.31-7.61]) was associated with an increased risk of severe malaria. These findings strongly support the hypothesis that maternal factors are central to the development of severe malaria in children. Programmes aiming to improve both maternal health and maternal education may reduce the incidence of severe malaria in children and should therefore be advocated in Bamako and in areas with similar epidemiological patterns for malaria.

Adolescent↗

PubMed2002

Triangular test applied to the clinical trial of azithromycin against relapses in Plasmodium vivax infections.

BACKGROUND: Sequential analysis enables repeated statistical analyses to be performed throughout a trial recruitment period, while maintaining a pre-specified power and type I error. Thus the trial can be stopped as soon as the information accumulated is considered sufficient to reach a conclusion. Sequential tests are easy to use and their statistical properties are especially suitable to trials with very straightforward objectives such as non-comparative phase II trials. We report on a phase II study based on the triangular test (TT) aiming at assessing the effectiveness of azithromycin in preventing Plasmodium vivax relapses. METHODS: To test whether the P. vivax relapse rate was either <12% or >or= 45% in patients treated with azithromycin, a sequential analysis based on the TT was as used. Patients infected with P. vivax were treated with azithromycin, 1.2 g daily, for 7 days. The onset of a relapse infection was monitored. RESULTS: Five patients presenting with an acute P. vivax infection were included in the study. All the patients were initially cured. Three patients reported mild gastrointestinal adverse effects. When the third patient relapsed, the sample path crossed the upper boundary of the TT, and the trial was stopped. CONCLUSIONS: Using the triangular test, with only a small number of patients, we concluded that azithromycin was not effective enough in preventing P. vivax relapses to warrant further evaluation in phase III. It is suggested that a wider use of sequential analysis in phase II anti-infective drugs trials may have financial and ethical benefits.

Adolescent↗