Comparison of field and expert laboratory microscopy for active surveillance for asymptomatic Plasmodium falciparum and Plasmodium vivax in Western Thailand
Comparison of field and expert laboratory microscopy for active surveillance for asymptomatic Plasmodium falciparum and Plasmodium vivax in Western Thailand
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DOI：
10.4269/ajtmh.2002.67.141
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发表时间：
2002-08-01
影响因子：
3.3
通讯作者：
Sattabongkot, J
中科院分区：
文献类型：
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作者：
Coleman, RE;Maneechai, N;Sattabongkot, J
由熟练的显微镜学家对姬姆萨染色的厚膜和薄膜进行显微镜检查仍然是诊断疟疾的标准实验室方法。然而，用这种方法诊断疟疾是有问题的，因为结果的解释需要相当多的专业知识，特别是在低寄生虫水平。我们比较了“现场”和“专家实验室”显微镜在泰国西部恶性疟原虫和间日疟原虫主动监测的有效性。现场显微镜检查包括使用自然光源在x700下对厚膜进行约5分钟的读取（50-100个视野），而专家实验室显微镜检查包括使用高质量、维护良好的显微镜和人工光源在x1，000下进行20分钟的读取（每500个白细胞的寄生虫数量）。对所有不一致结果和20%的一致结果进行盲态交叉检查。2000年5月至11月期间收集的3，004张血片纳入研究，其中156张（5.2%）为恶性疟原虫阳性，177张（5.9%）为间日疟原虫阳性，4张（0.1%）为恶性疟原虫和间日疟原虫。总共84.4%（135/160）的恶性疟原虫阳性玻片和93.9%的间日疟原虫阳性玻片的寄生虫血症低于500/穆尔。现场镜检诊断恶性疟的特异性为99.3%，敏感性为10.0%，阳性预测值（PPV）为43.2%，阴性预测值（NPV）为95.1%。诊断间日疟的特异性和敏感性分别为99.2%和7.1%，PPV为38.7%，NPV为93.9%。本研究中定义的现场显微镜检查不是泰国西部疟疾主动监测的有效方法，因为那里的流行率和寄生虫血症率都很低。
Microscopy of Giemsa-stained thick and thin films by a skilled microscopist has remained the standard laboratory method for the diagnosis of malaria. However, diagnosis of malaria with this method is problematic since interpretation of results requires considerable expertise, particularly at low parasite levels. We compared the efficacy of "field" and "expert laboratory" microscopy for active surveillance of Plasmodium falciparum and P. vivax in western Thailand. Field microscopy consisted of an approximately five-minute read (50-100 fields) of a thick film at x700 using a natural light source, whereas expert laboratory microscopy consisted of a 20-minute read (number of parasites per 500 leukocytes) at x1,000 using a high-quality, well-maintained microscope with an artificial light source. All discordant and 20% of concordant results were cross-checked blindly. A total of 3,004 blood films collected between May and November 2000 were included in the study, of which 156 (5.2%) were positive for P. falciparum, 177 (5.9%) for P. vivax, and 4 (0.1%) for both P. falciparum and P. vivax by expert microscopy. A total of 84.4% (135 of 160) of the P. falciparum-positive slides and 93.9% of the P. vivax-positive slides had a parasitemia of less than 500/muL. Field microscopy was specific (99.3%) but not sensitive (10.0%) for the diagnosis of P. falciparum malaria, with a positive predictive value (PPV) of 43.2% and a negative predictive value (NPV) of 95.1%. The corresponding specificity and sensitivity for the diagnosis of P. vivax malaria were 99.2% and 7.1%, respectively, with a PPV of 38.7% and an NPV of 93.9%. Field microscopy, as defined in this study, is not an effective method for active malaria surveillance in western Thailand, where prevalence and parasitemia rates are low.