Williams Geoffrey S, Mweya Clement, Stewart Laveta, Mtove George, Reyburn Hugh, Cook Jackie, Corran Patrick H, Riley Eleanor M, Drakeley Chris J
Joint Malaria Programme, Kilimanjaro Christian Medical Centre, Moshi, Tanzania.
Malar J. 2009 Jul 22;8:168. doi: 10.1186/1475-2875-8-168.
Sero-epidemiological methods are being developed as a tool for rapid assessment of malaria transmission intensity. Simple blood collection methods for use in field settings will make this more feasible. This paper describes validation of such a method, by analysing immunoglobulins from blood retained within immunophoretic rapid diagnostic tests (RDTs) for Plasmodium falciparum. RDTs are now widely used for the diagnosis of malaria and estimation of parasite rates, and this method represents a further use for these devices in malaria control.
Immunoglobulins eluted from RDTs, designed to detect parasite histidine rich protein-2 (HRP-2), were analysed by indirect ELISA for IgG recognizing the P. falciparum blood stage antigens merozoite surface protein-1(19) (MSP-1(19)) and apical membrane antigen-1 (AMA-1). Optimal storage conditions for RDTs were evaluated by comparing antibody responses from RDTs stored in dry or humid conditions at 4 degrees C or at ambient temperature (with or without air-conditioning) for 7, 31 or 70 days. Antibody levels estimated using 3,700 RDT samples from attendees at health facilities in North-eastern Tanzania were compared with contemporaneously collected filter paper blood spots (FPBS) and used to estimate seroconversion rates.
Storage of RDTs at 4 degrees C was optimal for immunoglobulin recovery but short-term storage at ambient temperatures did not substantially affect anti-malarial IgG levels. Results from RDTs were comparable with those from FPBSs, for both antigens. RDT-generated titres tended to be slightly higher than those generated from FPBSs, possibly due to greater recovery of immunoglobulins from RDTs compared to filter paper. Importantly, however, RDT-based seroconversion rates, and hence serological estimates of malaria transmission intensity, agreed closely with those from FPBSs.
RDTs represent a practical option for collecting blood for sero-epidemiological surveys, with potential cost and logistical advantages over filter paper and other blood collection methods. RDT-based seroepidemiology can be incorporated into routine monitoring of malaria endemicity, providing information to supplement parasite prevalence rates and generating rapid, robust assessment of malaria transmission intensity at minimal extra cost.
血清流行病学方法正被开发为一种快速评估疟疾传播强度的工具。适用于现场环境的简单血液采集方法将使其更具可行性。本文通过分析用于恶性疟原虫免疫电泳快速诊断试验（RDT）中留存血液的免疫球蛋白，描述了该方法的验证过程。RDT目前广泛用于疟疾诊断和寄生虫率估算，而此方法代表了这些设备在疟疾防控中的进一步应用。
通过间接ELISA分析从旨在检测寄生虫富含组氨酸蛋白-2（HRP-2）的RDT中洗脱的免疫球蛋白，以检测识别恶性疟原虫血液期抗原裂殖子表面蛋白-1（19）（MSP-1（19））和顶端膜抗原-1（AMA-1）的IgG。通过比较在4℃或室温（有或无空调）下干燥或潮湿条件下储存7、31或70天的RDT的抗体反应，评估RDT的最佳储存条件。将使用来自坦桑尼亚东北部医疗机构就诊者的3700份RDT样本估算的抗体水平与同期采集的滤纸血斑（FPBS）进行比较，并用于估算血清转化率。
RDT在4℃下储存最有利于免疫球蛋白回收，但在室温下短期储存对抗疟IgG水平影响不大。对于两种抗原，RDT的结果与FPBS的结果相当。RDT产生的滴度往往略高于FPBS产生的滴度，这可能是因为与滤纸相比，从RDT中回收的免疫球蛋白更多。然而，重要的是，基于RDT的血清转化率以及因此对疟疾传播强度的血清学估计与FPBS的结果非常一致。
RDT是血清流行病学调查采血的一种实用选择，与滤纸和其他血液采集方法相比，具有潜在的成本和后勤优势。基于RDT的血清流行病学可纳入疟疾流行程度的常规监测，提供信息以补充寄生虫流行率，并以最小的额外成本对疟疾传播强度进行快速、可靠的评估。
