Yale School of Public Health, New Haven, CT, USA.
Infectious Diseases Research Collaboration, Kampala, Uganda.
BMC Infect Dis. 2019 Jun 26;19(1):559. doi: 10.1186/s12879-019-4174-1.
Blood smear microscopy remains the gold-standard method to diagnose and quantify malaria parasite density. In addition, parasite genotyping of select loci is the most utilized method for distinguishing recrudescent and new infections and to determine the number of strains per sample. In research settings, blood may be obtained from capillary or venous compartments, and results from these matrices have been used interchangeably. Our aim was to compare quantitative results for parasite density and strain complexity from both compartments.
In a prospective observational study, children and adults presenting with uncomplicated Plasmodium falciparum malaria, simultaneous capillary and venous blood smears and dried blood spots were collected over 42-days following treatment with artemether-lumefantrine. Blood smears were read by two microscopists, any discrepancies resolved by a third reader. Parasite DNA fingerprinting was conducted using six microsatellites. Bland Altman analysis and paired t-test/McNemar's test were used to assess the difference in density readings and measurements.
Two hundred twenty-three participants were included in the analysis (177 children (35 HIV-infected/142 HIV-uninfected), 21 HIV-uninfected pregnant women, and 25 HIV-uninfected non-pregnant adults). Parasite density measurements did not statistically differ between capillary and venous blood smears at the time of presentation, nor over the course of 42-day follow-up. Characterization of merozoite surface protein-2 (MSP-2) genetic polymorphism demonstrated a higher level of strain diversity at the time of presentation in venous samples, as compared with capillary specimens (p = 0.02). There was a high degree of variability in genotype-corrected outcomes when pairs of samples from each compartment were compared using MSP-2 alone, although the variability was reduced with the use of multiple markers.
Parasite density measurements do not statistically differ between capillary and venous compartments in all studied demographic groups at the time of presentation with malaria, or over the course of follow-up. More strains were detected by MSP-2 genotyping in venous samples than in capillary samples at the time of malaria diagnosis. The use of multiple polymorphic markers reduces the impact of variability in strain detection on genotype-corrected outcomes. This study confirms that both capillary and venous compartments can be used for sampling with confidence in the clinical research setting.
The trial was registered at ClinicalTrials.gov under registration no. NCT01717885 .
血涂片显微镜检查仍然是诊断和定量疟原虫密度的金标准方法。此外，选择位点的寄生虫基因分型是区分复发和新感染以及确定每个样本中菌株数量的最常用方法。在研究环境中，血液可从毛细血管或静脉腔获得，并且这些基质的结果可互换使用。我们的目的是比较来自两个腔室的寄生虫密度和菌株复杂性的定量结果。
在一项前瞻性观察研究中，对接受青蒿琥酯-甲氟喹治疗后 42 天内出现无并发症间日疟原虫感染的儿童和成人同时采集毛细血管和静脉血涂片和干血斑。两名显微镜检查者阅读血涂片，由第三名读者解决任何差异。使用六个微卫星进行寄生虫 DNA 指纹分析。使用 Bland Altman 分析和配对 t 检验/McNemar 检验评估密度读数和测量值的差异。
共有 223 名参与者纳入分析（177 名儿童（35 名 HIV 感染/142 名 HIV 未感染），21 名 HIV 未感染孕妇和 25 名 HIV 未感染非孕妇成人）。在就诊时，毛细血管和静脉血涂片之间的寄生虫密度测量值没有统计学差异，在 42 天的随访过程中也没有统计学差异。在就诊时，对裂殖子表面蛋白-2（MSP-2）遗传多态性的特征描述表明，与毛细血管标本相比，静脉样本中的菌株多样性更高（p=0.02）。当使用 MSP-2 单独比较每个腔室的样本对时，基因型校正结果存在很大的变异性，尽管使用多个标记物可以降低变异性。
在所有研究的人群中，在疟疾就诊时，毛细血管和静脉腔室之间的寄生虫密度测量值在统计学上没有差异，在随访过程中也没有差异。在疟疾诊断时，通过 MSP-2 基因分型在静脉样本中检测到的菌株比在毛细血管样本中更多。使用多个多态性标记物可减少菌株检测变异性对基因型校正结果的影响。这项研究证实，在临床研究环境中，毛细血管和静脉腔都可以有信心地用于采样。
该试验在 ClinicalTrials.gov 注册，注册号为 NCT01717885。
