Nuffield Department of Clinical Laboratory Sciences, University of Oxford, and National Health Service Blood and Transplant, John Radcliffe Hospital, Headington, Oxford, OX3 9DU, UK.
Malar J. 2012 Jun 15;11:201. doi: 10.1186/1475-2875-11-201.
Estimation of Plasmodium falciparum parasitaemia can vary with the method used and time of sampling. Quantitative real time PCR (qPCR) on whole blood or plasma samples has previously been shown to be more sensitive than thick film microscopy. However the efficiencies of each method have not been compared using samples obtained from infants less than one year old.
A multiple of statistical approaches were used to compare the performance of qPCR on whole blood or plasma to detect the 18 S ribosomal gene of P. falciparum in 548 samples from children aged 2.5 or 24 months. Parasite prevalence in matched samples was compared using Mcnemar's test and agreement of positive results quantified as Kappa scores. Parasite prevalences between different age groups were compared by Fisher's test. Results from analyses by thick film microscopy were also available from children at 24 months and their correlation to each qPCR method examined by the Spearman's test. Finally the association of P. falciparum infection with the incidence of multiple malaria episodes from contact to 24 months of age was evaluated using negative binomial regression.
These analyses showed that qPCR from whole blood detected approximately 3-fold more cases of infection than plasma qPCR. Both qPCR methods agreed well with each other although qPCR from plasma had a greater agreement with microscopy (96.85%) than did qPCR from blood (69.7%). At 24 months the prevalence of infection detected by all methods was associated with anaemia (p<0.05).
The data presented here demonstrates that low levels of parasitaemia are better detected by qPCR using parasite DNA from whole blood than from plasma. However plasma samples provide a viable substitute when parasite smears are unavailable.
疟原虫感染的估计可能因所用方法和采样时间而异。全血或血浆样本的实时定量 PCR（qPCR）以前被证明比厚涂片显微镜检查更敏感。然而，以前尚未使用从不到 1 岁的婴儿获得的样本比较每种方法的效率。
使用多种统计方法比较了 qPCR 检测全血或血浆中恶性疟原虫 18S 核糖体基因的性能，以检测 2.5 或 24 月龄儿童的 548 个样本。使用 McNemar 检验比较匹配样本中的寄生虫流行率，并通过 Kappa 评分量化阳性结果的一致性。Fisher 检验比较不同年龄组之间的寄生虫流行率。24 月龄儿童也可获得厚涂片显微镜检查的结果，并通过 Spearman 检验检查其与每种 qPCR 方法的相关性。最后，使用负二项回归评估从接触到 24 月龄时，恶性疟原虫感染与多次疟疾发作的发生率之间的关系。
这些分析表明，qPCR 从全血中检测到的感染病例约为血浆 qPCR 的 3 倍。两种 qPCR 方法彼此之间非常吻合，尽管与显微镜检查相比，血浆 qPCR 的吻合度更高（96.85%），而不是血液 qPCR（69.7%）。在 24 月龄时，所有方法检测到的感染流行率与贫血有关（p<0.05）。
这里提出的数据表明，与从血浆中使用寄生虫 DNA 相比，使用全血中的 qPCR 可以更好地检测到低水平的寄生虫血症。然而，当寄生虫涂片不可用时，血浆样本是可行的替代品。
