Nico Nagelkerke

Seroprevalence of dengue antibodies, annual incidence and risk factors among children in southern Vietnam

Dengue is highly endemic in southern Vietnam and all four serotypes of dengue virus have already been identified. To determine the age‐specific prevalence of dengue and associated risk factors, we conducted a serological study at two primary schools and assessed risk factors by analysing childrens questionnaires and household surveys. Sera were collected from 961 primary schoolchildren in Binh Thuan Province and tested for the presence of dengue virus serum antibodies using an indirect immunoglobulin G (IgG) enzyme‐linked immunosorbent assay (ELISA). The antibody prevalence of the total population was 65.7% (nu2003=u2003631) which increased from 53.0 to 88.2% with age. The annual incidence of a first dengue infection, estimated by binary regression of the seroprevalence by age, was 11.7%. Interestingly, the prevalence of dengue IgG antibodies was significantly higher in children who confirmed using a pit latrine (RR 1.467, 95% CI: 1.245–1.730) and whose domestic environment contained discarded cans (RR 1.238, 95% CI: 1.042–1.470) and pigs (RR 1.228, 95% CI: 1.002–1.504). The epidemiology of dengue in southern Vietnam is stable with a constantly high annual incidence of first infections. Transmission occurs mainly peri‐domestically, which has important public health implications.

Histological age prediction from the femur in a contemporary Dutch sample. The decrease of nonremodeled bone in the anterior cortex.

ABSTRACT: This paper presents an uncomplicated and minimally invasive method for age‐at‐death determination in a contemporary Dutch (West European) population, by modifying the approach of assessment based on the age‐related remodeling of bone tissue. In contrast to the usual “osteon count,” a “non‐remodeled tissue count” is undertaken. To optimize the method, proper zeroing of the polarization filter set of the microscope is essential. Instructions for setting the filters are given. A sample of femoral shaft segments totaling 162 individuals with ages ranging from 15 to 96 years is analyzed. Subperiosteal quantitative assessments are recorded at the most anterior point of the femoral shaft and also at points 25° to the left and to the right of that point. Interobserver agreement in the assessments shows an acceptable degree of correlation. Bone remodeling with age does not progress in a linear, but in a curvilinear manner. Dependence of predicted age on nonremodeled surface counts in the analyzed areas of the anterior cortex of the femur appears to be significant. A set of regression equations is given. Sex can be ignored in age prediction. The small but statistically significant dependence of predicted age on cadaver length corresponds with the present strong secular increase in stature in the Netherlands. A concise catalogue with micrograph examples for every 10‐year period in life is available upon request.

Malaria control in Vietnam: the Binh Thuan experience

Objectiveu2002 The National Malaria Control Program (NMCP) in Vietnam is based on application of insecticide‐treated bed nets (ITNs), spraying of insecticides and early microscopic diagnosis of malaria and treatment (EDTM) with artemisinin drugs. This study explores the implementation of the NMCP at provincial level and its impact on malaria incidence (mi) and prevalence in Binh Thuan in southern Vietnam.

Uptake of Onchocerca volvulus (Nematoda: Onchocercidae) by Simulium (Diptera: Simuliidae) is not strongly dependent on the density of skin microfilariae in the human host.

Abstract The relation between the number of microfilariae (mf) ingested by host-seeking vectors of human onchocerciasis and skin mf load is an important component of the population biology of Onchocerca volvulus, with implications for disease control and evaluation of the risk of transmission recrudescence. The microsimulation model ONCHOSIM has been used to assess such risk in the area of the Onchocerciasis Control Program (OCP) in West Africa, based on a strongly nonlinear relation between vector mf uptake and human mf skin density previously published. However, observed levels of recrudescence have exceeded predictions, warranting a recalibration of the model. To this end, we present the results of a series of fly-feeding experiments carried out in savanna and forest localities of West Africa. Flies belonging to Simulium damnosum s.s., S. sirbanum, S. soubrense, and S. leonense were fed on mf carriers and dissected to assess the number of ingested mf escaping imprisonment by the peritrophic matrix (the number of exo-peritrophic mf), a predictor of infective larval output. The method of instrumental variables was used to obtain (nearly) unbiased estimates of the parameters of interest, taking into account error in the measurement of skin mf density. This error is often neglected in these types of studies, making it difficult to ascertain the degree of density-dependence truly present in the relation between mf uptake and skin load. We conclude that this relation is weakly (yet significantly) nonlinear in savanna settings but indistinguishable from linearity in forest vectors. Exo-peritrophic mf uptake does not account for most of the density dependence in the transmission dynamics of the parasite as previously thought. The number of exo-mf in forest simuliids is at least five times higher than in the savanna vectors. Parasite abundance in human onchocerciasis is regulated by poorly known mechanisms operating mainly on other stages of the lifecycle.

Automated detection of malaria pigment: feasibility for malaria diagnosing in an area with seasonal malaria in northern Namibia

Objectiveu2002 To evaluate the feasibility of automated malaria detection with the Cell‐Dyn® 3700 (Abbott Diagnostics, Santa Clara, CA, USA) haematology analyser for diagnosing malaria in northern Namibia.

Breast Cancer Screening, Outside the Population-Screening Program, of Women from Breast Cancer Families without Proven BRCA1/BRCA2 Mutations: a Simulation Study

Purpose: We assessed the cost-effectiveness of mammography screening for women under the age of 50, from breast cancer families without proven BRCA1/BRCA2 mutations, because current criteria for screening healthy women from breast cancer families are not evidence-based. Methods: We did simulation studies with mathematical models on the cost-effectiveness of mammography screening of women under the age of 50 with breast cancer family histories. Breast cancer screening was simulated with varying screening intervals (6, 12, 18, and 24 months) and screening cohorts (starting at ages 30, 35, 40, and 45, and continuing to age 50). Incremental costs of screening were compared with those of women ages 50 to 52 years, the youngest age group currently routinely screened in the nationwide screening program of the Netherlands, to determine cost-effectiveness. Sensitivity analyses were done to explore the effects of model assumptions. The cost-effectiveness of breast cancer screening for women over the age of 50 was not debated. Results: The most effective screening interval was found to be 12 months, which, however, seems only to be cost-effective in a small group of women under the age of 50 with at least two affected relatives, including at least one affected in the first degree diagnosed under the age of 50. Significantly, early breast cancer screening never seemed to be cost-effective in women with only one affected first-degree or second-degree relative. Conclusion: Annual breast cancer screening with mammography for women under the age of 50 seems to be cost-effective in women with strong family histories of breast cancer, even when no BRCA1/BRCA2 mutation was found in affected family members. (Cancer Epidemiol Biomarkers Prev 2006;15(3):429–36)

Breast cancer screening, outside the population-screening program, of women from breast cancer families without proven BRCA1/BRCA2 mutations: a simulation study

Purpose: We assessed the cost-effectiveness of mammography screening for women under the age of 50, from breast cancer families without proven BRCA1/BRCA2 mutations, because current criteria for screening healthy women from breast cancer families are not evidence-based. Methods: We did simulation studies with mathematical models on the cost-effectiveness of mammography screening of women under the age of 50 with breast cancer family histories. Breast cancer screening was simulated with varying screening intervals (6, 12, 18, and 24 months) and screening cohorts (starting at ages 30, 35, 40, and 45, and continuing to age 50). Incremental costs of screening were compared with those of women ages 50 to 52 years, the youngest age group currently routinely screened in the nationwide screening program of the Netherlands, to determine cost-effectiveness. Sensitivity analyses were done to explore the effects of model assumptions. The cost-effectiveness of breast cancer screening for women over the age of 50 was not debated. Results: The most effective screening interval was found to be 12 months, which, however, seems only to be cost-effective in a small group of women under the age of 50 with at least two affected relatives, including at least one affected in the first degree diagnosed under the age of 50. Significantly, early breast cancer screening never seemed to be cost-effective in women with only one affected first-degree or second-degree relative. Conclusion: Annual breast cancer screening with mammography for women under the age of 50 seems to be cost-effective in women with strong family histories of breast cancer, even when no BRCA1/BRCA2 mutation was found in affected family members. (Cancer Epidemiol Biomarkers Prev 2006;15(3):429–36)

Breast cancer screening, outside the population-screening program, of women from breast cancer families without proven BRCA1/BRCA2 mutations

Purpose: We assessed the cost-effectiveness of mammography screening for women under the age of 50, from breast cancer families without proven BRCA1/BRCA2 mutations, because current criteria for screening healthy women from breast cancer families are not evidence-based. Methods: We did simulation studies with mathematical models on the cost-effectiveness of mammography screening of women under the age of 50 with breast cancer family histories. Breast cancer screening was simulated with varying screening intervals (6, 12, 18, and 24 months) and screening cohorts (starting at ages 30, 35, 40, and 45, and continuing to age 50). Incremental costs of screening were compared with those of women ages 50 to 52 years, the youngest age group currently routinely screened in the nationwide screening program of the Netherlands, to determine cost-effectiveness. Sensitivity analyses were done to explore the effects of model assumptions. The cost-effectiveness of breast cancer screening for women over the age of 50 was not debated. Results: The most effective screening interval was found to be 12 months, which, however, seems only to be cost-effective in a small group of women under the age of 50 with at least two affected relatives, including at least one affected in the first degree diagnosed under the age of 50. Significantly, early breast cancer screening never seemed to be cost-effective in women with only one affected first-degree or second-degree relative. Conclusion: Annual breast cancer screening with mammography for women under the age of 50 seems to be cost-effective in women with strong family histories of breast cancer, even when no BRCA1/BRCA2 mutation was found in affected family members. (Cancer Epidemiol Biomarkers Prev 2006;15(3):429–36)