The effect of altitude on parasite density case definitions for malaria in northeastern Tanzania
The effect of altitude on parasite density case definitions for malaria in northeastern Tanzania
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DOI：
10.1111/j.1365-3156.2006.01672.x
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发表时间：
2006-08-01
影响因子：
3.3
通讯作者：
Carneiro, Ilona
中科院分区：
文献类型：
--
作者：
Chandler, Clare I. R.;Drakeley, Chris J.;Carneiro, Ilona
目标 疟疾临床试验需要精确的终点来衡量疗效。在无症状寄生虫血症常见的流行地区，“发烧加寄生虫血症”可能无法区分疟疾病例和非病例。基于寄生虫截止密度的病例定义可能更合适，但可能随年龄和传播强度而变化。本研究检查了在广泛的传播强度范围内进行的寄生虫学调查中的适当病例定义，并使用海拔高度作为传播强度的代理。方法从坦桑尼亚东北部流行区不同海拔的 24 个村庄收集的横断面数据，采用改进的泊松回归方法计算疟疾归因分数。我们将发烧建模为寄生虫密度的函数，并使用敏感性和特异性分析确定引起发烧的寄生虫的最佳截止密度。结果 5 岁以下儿童的最佳截止密度因海拔而异：海拔 < 600 m 时每毫升 4000 只寄生虫（高传播强度）的病例定义是最合适的，而海拔 > 600 m 时每毫升 1000 只寄生虫（低传播强度）是最合适的。强度）。在 5 岁以上儿童和成人中，海拔差异很小，任何寄生虫加发烧的病例定义是最合适的。 结论 出于研究目的，应使用适合当地的疟疾病例定义。在我们的环境中，这些随着年龄和传播强度而独立变化。
OBJECTIVES Malaria clinical trials need precise endpoints to measure efficacy. In endemic areas where asymptomatic parasitaemia is common, 'fever plus parasitaemia' may not differentiate between malaria cases and non-cases. Case definitions based on parasite cut-off densities may be more appropriate but may vary with age and transmission intensity. This study examines appropriate case definitions from parasitological surveys conducted over a broad range of transmission intensities, using altitude as a proxy for transmission intensity.METHODS Cross-sectional data collected from 24 villages at different altitudes in an endemic area of northeastern Tanzania were used to calculate malaria-attributable fractions using a modified Poisson regression method. We modelled fever as a function of parasite density and determined the optimum cut-off densities of parasites to cause fever using sensitivity and specificity analyses.RESULTS The optimum cut-off density varied by altitude in children aged under 5 years: a case definition of 4000 parasites per mu l at altitudes < 600 m (high transmission intensity) was most appropriate, compared with 1000 parasites per mu l at altitudes > 600 m (low transmission intensity). In children aged over 5 years and adults, there was little variation by altitude and a case definition of any parasites plus fever was the most appropriate.CONCLUSIONS Locally appropriate case definitions of malaria should be used for research purposes. In our setting, these varied independently with age and transmission intensity.