Laboratory diagnosis of malaria
Laboratory diagnosis of malaria
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DOI：
10.1136/jcp.49.7.533
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发表时间：
1996-07-01
影响因子：
3.4
通讯作者：
Williams, JE
中科院分区：
文献类型：
--
作者：
Warhurst, DC;Williams, JE
对于疟疾诊断，理想情况下应直接从患者的手指或耳朵采血，并在床边或诊所制备涂片。胶片与载玻片的粘附性更好，裂解后留下更清晰的背景，寄生虫和红细胞的变化最小。如果有必要使用抗凝血剂，那么应该尽快制作薄膜，当然在抽血后的三小时内。EDTA在这方面优于其他抗凝剂。如果血液中使用抗凝剂时间过长，会严重影响寄生虫和红细胞形态。有性阶段的进一步发育可能会发生（在适当的条件下甚至在20分钟内），释放到血浆中的雄性配子可能被误认为是其他生物体，如疏螺旋体。它们可以通过红色染色核的中心位置和没有明显的、重复的弯曲曲线来与伯氏疏螺旋体区分。如果被寄生的血液被放在温暖的实验室温度下，释放出来的分裂子可能会侵入红细胞。例如，这可能导致在间日疟原虫寄生的血液中出现相当数量的“accole”形式，这是恶性疟原虫的特征。由于血液样本中酸的积累，较重的寄生虫血症持续数小时可能导致本已脆弱的被寄生红细胞严重恶化。那些被早期间日疟原虫寄生的人可能会缩小或变大。寄生虫的后期阶段可能变得致密，红细胞膜可能变得非常脆弱，因此在制备薄膜时可以拉伸。长时间接触，超过10-12小时，可能导致间日疟原虫后期阶段的完全破坏，使识别变得困难，甚至在某些情况下无法识别。如有可能，应在退热期间或之后以及服用抗疟疾药物之前采血。药物治疗除了使寄生虫病更难被发现外，还会导致寄生部位出现令人困惑的形态变化。例如，氯喹会导致色素囊泡聚集，并可能导致其他物种被误认为是恶性疟原虫。如果有骨髓活检标本，这可能是疟疾诊断的有效标本。褐色被毛涂片可能对少量成熟阶段和配子体的检测有用，但不建议常规使用。对于疟疾的常规诊断，应准备四张薄血膜和四张厚血膜。其中一层用吉氏染色的薄膜应足以用于正常寄生虫病的检测和种类的确定。为了节省时间，必要时，可以使用快速菲尔德技术，但应以吉姆萨染色薄膜为后盾。厚膜应使用Giemsa染色或Field染色。如果诊断出现问题，其他片子可作进一步研究。此外，PHLS疟疾参考实验室将感谢未染色的薄膜，无论厚的还是薄的，以供确认。（疟疾在英国是法定疾病。）如果
Samples for blood film diagnosis For malaria diagnosis blood should ideally be taken direct from the patient's finger or ear and the smears prepared at the bedside or in the clinic. Films adhere better to the slides, leave a clearer background after lysis, and parasite and red cell changes are minimal. If it is necessary to use anticoagulants, then the films should be made as soon as possible, certainly less than three hours, after the blood was drawn. EDTA is superior to other anticoagulants for this purpose. Parasite and red blood cell morphology can be seriously affected if the blood has been in anticoagulant for too long. 3 Further development of the sexual stages may occur (even within 20 minutes under the right conditions) and the male gametes re-leased into the plasma may be mistaken for other organisms, such as Borrelia. They may be distinguished from Borrelia by the central loca-tion of the red-staining nucleus, and the absence of notable, repetitive sinuous curves. If parasitised blood is left at warm laboratory temperature, red cells may be invaded by released merozoites. This may lead-for exam-ple, to the occurrence of appreciable numbers of" accole" forms, characteristic of P falciparum, in blood parasitised by P vivax. Heavier parasitaemias left for several hours may lead to the serious deterioration of the already delicate parasitised erythrocytes, owing to a build-up of acid in the blood sample. Those parasitised with early P vivax forms may shrink or become crenated. Later stages of the parasite may become compact, and the eryth-rocyte membrane may become very delicate so that it stretches when the film is prepared. Pro-longed exposure, for more than 10-12 hours, may result in the total destruction of the later stages of P vivax, making recognition difficult or, in some instances, impossible. Blood should, if possible, be taken during or after pyrexia, and before the administration of antimalarial drugs. Drug treatment, besides making parasitaemia harder to detect, causes confusing morphological changes in the para-sites. Chloroquine-for example, causes clumping of pigment vesicles and can lead to other species being mistaken for Pfalciparum. Where a bone marrow biopsy specimenis available, this may be a fruitful specimen for malaria diagnosis. Buffy coat smears may be useful for the detection of scanty maturing stages and gametocytes, but are not recom-mended routinely.For routine diagnosis of malaria, four thin and four thick blood films should be prepared. One of the thin films, stained with Giemsa, should be adequate for detection of normal parasitaemias and for determination of species. To save time, where essential, the rapid Field's technique may be used, but should be backed up by Giemsa stained thin films. The thick films should be stained using Giemsa or Field's stain. Ifproblems with diagnosis arise the other films are available for further study. In addition, the PHLS Malaria Reference Laboratory would appreciate having unstained films, both thick and thin, for confirmation.(Malaria isa notifiable disease in the UK.) If