Ali Mohamed Siddig M, Yousif Abdul Gader Mohamed, Mustafa Mustafa Salih, Ibrahim Malik Hassan
Department of Haematology, AI Neelain University, Khartoum, Sudan.
Clin Lab Sci. 2005 Spring;18(2):69-73.
To compare the standard microscopic examination, the polymerase chain reaction (PCR), and the immunochromatography test (ICT) to determine the best method for screening blood donors for malaria parasites in Sudan.
A total of 100 blood donors were screened for malaria parasites by standard microscopic technique, ICT, and PCR Blood films were examined microscopically using standard Giemsa staining techniques. Qurum (Canadian Company) malaria kits were used to perform the ICT. For performing PCR, DNA was extracted using Chelex method and amplified by the moderately repetitive DNA sequence pBRK-l.
Using PCR, a total of 21 blood samples were positive; 8 (38%) of them showed negative blood films and 7 (33%) were negative on ICT. Four blood samples that tested positive by ICT despite a negative PCR and microscopic examination were proved to be false positives. The false negativity of both the microscopic examination and ICT was found to be significant. The sensitivity of microscopy was 61.9% and of ICT was 66.7%, while the specificity of microscopy was 100% and of ICT was 94.9%. When direct microscopy was considered as the standard technique the sensitivity of ICT was 100% and the specificity was 94.3%.
Although PCR is more sensitive and more specific, it is unaffordable. Microscopy for malaria when compared to ICT showed similar sensitivity at low cost. However, all human plasmodium species can be detected using the microscopy while only two species (P. falciparum and P. vivax) can be detected by ICT. The detected false positivity of ICT is not inconsequential since this implies the rejection of a greater proportion of blood donations. Therefore, microscopy is considered more suitable for screening Sudanese blood donors for malaria parasites prior to donation at the present time.
To establish a reference malaria diagnosis unit in each blood bank in Sudan as well as to train blood bankers to perform microscopic examinations.
比较标准显微镜检查、聚合酶链反应（PCR）和免疫层析试验（ICT），以确定苏丹筛查献血者疟原虫的最佳方法。
采用标准显微镜技术、ICT和PCR对100名献血者进行疟原虫筛查。血涂片采用标准吉姆萨染色技术进行显微镜检查。使用Qurum（加拿大公司）疟疾检测试剂盒进行ICT。进行PCR时，采用Chelex法提取DNA，并通过中度重复DNA序列pBRK-1进行扩增。
使用PCR检测，共有21份血样呈阳性；其中8份（38%）血涂片呈阴性，7份（33%）ICT检测呈阴性。4份尽管PCR和显微镜检查均为阴性但ICT检测呈阳性的血样被证明为假阳性。显微镜检查和ICT的假阴性均具有显著性。显微镜检查的敏感性为61.9%，ICT的敏感性为66.7%，而显微镜检查的特异性为100%，ICT的特异性为94.9%。当将直接显微镜检查视为标准技术时，ICT的敏感性为100%，特异性为94.3%。
虽然PCR更敏感、更特异，但成本过高。与ICT相比，疟疾显微镜检查在低成本下显示出相似的敏感性。然而，使用显微镜检查可以检测到所有人类疟原虫种类，而ICT只能检测到两种（恶性疟原虫和间日疟原虫）。ICT检测到的假阳性并非无关紧要，因为这意味着更多比例的献血被拒收。因此，目前显微镜检查被认为更适合在苏丹献血前筛查献血者的疟原虫。
在苏丹的每个血库建立一个参考疟疾诊断单位，并培训血库工作人员进行显微镜检查。
