ATTRIBUTABLE FRACTION ESTIMATES AND CASE DEFINITIONS FOR MALARIA IN ENDEMIC AREAS
ATTRIBUTABLE FRACTION ESTIMATES AND CASE DEFINITIONS FOR MALARIA IN ENDEMIC AREAS
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DOI：
10.1002/sim.4780132206
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发表时间：
1994-11-30
影响因子：
2
通讯作者：
HAYES, R
中科院分区：
文献类型：
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作者：
SMITH, T;SCHELLENBERG, JA;HAYES, R
疟疾寄生虫的无症状携带在流行地区经常发生，在发热者的血膜中检测到寄生虫并不一定表明临床疟疾。在低和中等流行地区，可以将发热病例中的寄生虫流行率与社区对照中的寄生虫流行率进行比较，以估计可归因于疟疾的病例的比例。在传播率很高的地区，这种对归属比例的估计可能不准确，因为几乎没有人没有寄生虫，此外，非疟疾发热似乎抑制了低水平的寄生虫血症，导致对归属比例的估计有偏差。因此，利用1959-1991年期间从坦桑尼亚一个高度流行地区收集的数据，探索了其他估计方法，那里80%以上的幼儿患有寄生虫病。Logistic回归方法将发烧风险建模为寄生虫密度的连续函数，比对寄生虫流行率的简单分析提供了更准确的估计，并克服了非疟疾发烧影响造成的偏差问题。这种模型可以用来估计任何个别病例是由疟疾引起的概率，并可加以扩展以考虑协变量。在流行地区广泛使用的有症状疟疾的病例定义要求发烧，并要求寄生虫密度超过特定的截止日期。通过使用从Logistic模型获得的概率来估计病例定义的敏感性和特异性，可以辅助选择截断值。
Asymptomatic carriage of malaria parasites occurs frequently in endemic areas and the detection of parasites in a blood film from a febrile individual does not necessarily indicate clinical malaria. In areas of low and moderate endemicity the parasite prevalence in fever cases can he compared with that in community controls to estimate the fraction of cases which are attributable to malaria. In areas of very high transmission such estimates of the attributable fraction may be imprecise because very few individuals are without parasites, Furthermore, non-malarial fevers appear to suppress low levels of parasitaemia resulting in biased estimates of the attributable fraction. Alternative estimation techniques were therefore explored using data collected during 1959-1991 from a highly endemic area of Tanzania, where over 80 per cent of young children are parasitaemic. Logistic regression methods which model fever risk as a continuous function of parasite density give more precise estimates than simple analyses of parasite prevalence and overcome problems of bias caused by the effects of non-malarial fevers. Such models can be used to estimate the probability that any individual episode is malaria-attributable and can be extended to allow for covariates. A case definition for symptomatic malaria that is used widely in endemic areas requires fever together with a parasite density above a specific cutoff. The choice of a cutoff value can be assisted by using the probabilities derived from the logistic model to estimate the sensitivity and specificity of the case definition.