Automated detection of malaria pigment: feasibility for malaria diagnosing in an area with seasonal malaria in northern Namibia

OBJECTIVE: To evaluate the feasibility of automated malaria detection with the Cell-Dyn 3700 (Abbott Diagnostics, Santa Clara, CA, USA) haematology analyser for diagnosing malaria in northern Namibia. METHODS: From April to June 2003, all patients with a positive blood smear result and a subset of patients with no suspicion of malaria were included. Blood smear and a venous blood sample (to determine haemoglobin, platelet and malaria pigment levels) were collected from each patient. Malaria pigment test characteristics, correlations with blood parameters and pigment clearance time were calculated. Finally, a subset of blood samples was run twice to evaluate the consistency of test outcome. RESULTS: Two hundred and eight patients were included. Ninety had a positive blood smear result of which 84 tested positive for malaria pigment and 118 patients had a negative blood smear result of which four tested positive for malaria pigment. Test characteristics as compared with microscopy were as follows: sensitivity 0.93, specificity 0.97, positive predictive value 0.95, negative predictive value 0.95. Rerun of the blood samples resulted in a change of diagnosis in 14%. After 4 weeks, 33% of patients with an initially positive pigment result still tested positive. Malaria pigment was found to be negatively correlated with haemoglobin. CONCLUSIONS: Automated detection of malaria pigment is a useful diagnostic tool in this semi-rural area. In low-risk malaria season, the test can be used for diagnosing malaria because of the high sensitivity. In high-risk malaria season, the test can be used for excluding malaria in case of a negative pigment result because of the high specificity.     

Comparison of different diagnostic techniques in Plasmodium falciparum cerebral malaria

BACKGROUND & OBJECTIVES: Plasmodium falciparum cerebral malaria remains a major health problem in India. The efficacy of treatment of cerebral malaria lies in its early diagnosis through rapid diagnostic methods. ParaSights-F test detects HRP-2 antigen secreted by parasitised red blood cells and quantitative buffy coat assay (QBC) is examination of buffy coat for the presence of malarial parasite stained with acridine orange. This study was performed to evaluate the effectiveness of ParaSight-F test and QBC assay as diagnostic methods in the patients of cerebral malaria. METHODS: Fifty clinically diagnosed patients of cerebral malaria were included in the study. ParaSight-F test, QBC and conventional blood smear examination was done. Patients who were in coma and there were no obvious features of bacterial or viral etiology were investigated for cerebral malaria by these diagnostic methods. RESULTS: ParaSight-F test, QBC and peripheral blood smears were examined. Patients were followed-up for signs of clinical recovery. ParaSight-F test was positive in 47 patients, QBC in 46 while blood smear examination was positive in 28 cases. INTERPRETATION & CONCLUSION: Sensitivity and specificity of ParaSight-F test were found to be 96.6 and 94% while QBC showed 97.8 and 100% respectively. ParaSight-F test and QBC were found to be novel methods for diagnosis of cerebral malaria especially in the cases where diagnosis can not be made by conventional blood smear examination due to low parasitaemia. These rapid diagnostic methods help in early therapeutic intervention.     

Comparison of a parasite lactate dehydrogenase-based immunochromatographic antigen detection assay (OptiMAL) with microscopy for the detection of malaria parasites in human blood samples

Microscopic examination of blood smears remains the gold standard for malaria diagnosis, but is labor-intensive and requires skilled operators. Rapid dipstick technology provides a potential alternative. A study was conducted in The Gambia to compare the performance of OptiMAL, an immunochromatographic antigen detection assay for the diagnosis of malaria using parasite lactate dehydrogenase, against standard microscopy in patients with suspected malaria. For initial diagnosis of Plasmodium falciparum, irrespective of stage, this assay had a sensitivity of 91.3%, a specificity of 92%, a positive predictive value of 87.2%, and a negative predictive value of 94.7%. The sensitivity of the test decreased markedly at parasitemias < 0.01%. This assay can be used for the diagnosis of malaria in areas where microscopy is not available and for urgent malaria diagnosis at night and at weekends, when routine laboratories are closed and when relatively inexperienced microscopists may be on duty.     

Changing trends in prevalence of different Plasmodium species with dominance of Plasmodium falciparum malaria infection in Aligarh (India)

ObjectiveTo determine the prevalence of malaria in Aligarh and analyze species dominance in different years over a decade.MethodsDiagnosis of malaria was done using microscopy as gold standard, rapid antigen detection assays and quantitative buffy coat (QBC) assays. Giemsa stained blood smear examination was done, thick and thin films were examined for presence of different Plasmodium spp. Rapid antigen detection assays employing detection of HRP-2 and parasite lactate dehydrogenase antigen (pLDH) by immunochromatography was done in patients whose blood smear found to be negative by conventional Giemsa slide examination. QBC was done in cases where there is strong clinical suspicion of malaria with blood smear negative, in patients with chronic malaria, splenomegaly, or in those patients who had inadequate treatment and for post-treatment follow up.ResultsPlasmodium vivax and Plasmodium falciparum were only species detected in our hospital. Overall prevalence of malaria in Aligarh was found to be 8.8%. The maximum prevalence of 20.1% was observed in year 2008 and lowest 2.3% in 2002.ConclusionsHigh prevalence of malaria is observed in this part of country with dominance of both species particularly Plasmodium falciparum should be monitored and factors accounting for occurrence should be studied to employ effective control measures.     

Sensitivity and specificity of an antigen detection ELISA for malaria diagnosis

Enzyme-linked immunosorbent assays (ELISAs) allow for the testing of large numbers of samples within a short time frame. We tested the sensitivity and specificity of a histidine-rich protein 2 (HRP2)-based, commercially available ELISA antigen detection assay for Plasmodium falciparum (Malaria Antigen CELISA; Cellabs, Sydney, Australia). A total of 700 whole blood samples obtained from symptomatic outpatients of malaria clinics along the Thai-Myanmar border were tested relative to blinded duplicate expert microscopy adjusted with species-specific polymerase chain reaction (PCR). PCR-adjusted microscopy showed that 79 (11.3%) were infected with P. falciparum, 118 (16.9%) with P. vivax, 1 (0.1%) with P. malariae, 7 (1.0%) with mixed infections (P. falciparum and P. vivax), and 495 (70.7%) were negative. The geometric mean parasite density for P. falciparum was 7547/muL (range: 12-363,810/muL). The overall sensitivity of the HRP2 ELISA for P. falciparum malaria was 98.8% (95% CI, 93.6-100%) and the specificity was 100% (95% CI, 99.5-100%). The positive and negative predictive values for the ELISA were 100% (95% CI, 96.5-100%) and 99.8% (95% CI, 99.1-100%), respectively. The results for P. falciparum were clearly superior to expert microscopy alone, particularly in mixed infections. Microscopy combined with ELISA reaches a sensitivity and specificity similar to PCR-adjusted microscopy for the diagnosis of P. falciparum while being considerably less expensive and faster. We conclude that ELISA serves as an excellent tool to augment microscopy as the gold standard for P. falciparum diagnosis in research settings and should be further evaluated for screening in blood banks.     

Field evaluation of the ICT Malaria Pf/Pv immunochromatographic test for the detection of asymptomatic malaria in a Plasmodium falciparum/vivax endemic area in Thailand

Rapid antigen assays provide an effective tool for the detection of malaria in symptomatic patients. However, the efficacy of these devices for detecting asymptomatic malaria, where parasite levels are normally significantly lower than in symptomatic patients, is less well established. We evaluated the efficacy of a new combined Plasmodium falciparum-Plasmodim vivax immunochromatographic test (ICT Malaria Pf/Pv) in a cross-sectional malaria survey of the village of Ban Kong Mong Tha, Kanchanaburi Provice, Thailand, from August to December 2000. A total of 1,976 bleeds were made from 559 individuals over the course of the study. Blinded microscopy of thick and thin blood films was used as the gold standard; all discordant and 10% of concordant results were cross-checked. Of 1,976 ICT Malaria Pf/Pv dipsticks tested, 98.3% (n = 1,943) performed as expected, as evidenced by the appearance of the control line. The ICT Malaria Pf/Pv test was both sensitive (100.0%) and specific (99.7 %) for the diagnosis of falciparum malaria with parasitemias of > or = 500 trophozoites/microL; however, only 15.9% (13/82) of infected individuals had parasitemia rates this high. When P. falciparum parasitemia rates were < 500/microL, the sensitivity of the diagnosis was only 23.3%, with a positive predictive value (PPV) and a negative predictive value (NPV) of 76.2 and 97.2%, respectively. The ICT Malaria Pf/Pv test was specific, but not sensitive, for the diagnosis of vivax malaria with parasite rates of > or = 500 trophozoites/microl, with sensitivity, specificity, PPV, and NPV of 66.7%, 99.9%, 66.7%, and 99.9%, respectively. At parasite rates of < 500/microL, corresponding values were 0.0%, 99.9%, 0%, and 95.1%. Because of the relatively high cost of these assays, low parasite rates found in the majority of asymptomatic individuals, and low sensitivity of this assay with rates of < 500/microl, use of this assay as a tool for active case detection is of limited value in western Thailand.     

Detection of Plasmodium falciparum histidine-rich protein II in saliva of malaria patients

Detection of Plasmodium falciparum parasites in patients with malaria necessitates drawing blood, which increases the risk of accidental infections and is poorly accepted in communities with blood taboos. Thus, non-invasive, cost-effective malaria tests that minimize the need for blood collection are needed. Plasmodium falciparum histidine-rich protein II (PfHRP II) levels in plasma and saliva were compared in malaria-positive and -negative patients in Ghana. Plasma and saliva obtained from 30 thick-film positive and 10 negative children were evaluated for PfHRP II by ELISA. Among the 30 children with positive blood smear, 16 (53%) were PfHRP II positive in plasma and 13 (43%) had PfHRP II positive saliva. The sensitivity of PfHRP II detection was 53% for plasma and 43% for saliva. The specificity was 100% with no false positive for both plasma and saliva when compared with blood smear. Thus, rapid detection of PfHRP II antigen in saliva may be a useful non-invasive and cost-effective malaria diagnostic technique.     

Automated detection of malaria-associated intraleucocytic haemozoin by Cell-Dyn CD4000 depolarization analysis

Laboratory tests for malaria are only performed if there is clinical suspicion of the disease, and a missed diagnosis contributes substantially to morbidity and mortality. Malaria parasites produce haemozoin, which is able to depolarize light and this allows the automated detection of malaria during routine complete blood count analysis (CBC) with some Abbott Cell-Dyn instruments. In this study, we evaluated the Cell-Dyn CD4000 with 831 blood samples submitted for malaria investigations. Samples were categorized as malaria negative (n = 417), convalescent malaria (n = 64) or malaria positive (n = 350) by reference to thin/thick film microscopy, 'rapid test' procedures, polymerase chain reaction analysis and clinical history. With regard to CD4000 depolarization analysis, a malaria positive CD4000 pattern was ascribed to samples that showed one or more abnormal depolarizing purple events, which corresponded to monocytes containing ingested malaria pigment (haemozoin). Positive CD4000 patterns were observed in 11 of 417, 50 of 64 and 281 of 350 of malaria negative, convalescent malaria and malaria positive samples respectively. The specificity and positive predictive values for malaria (active and convalescent) were very high (97.4 and 96.8%, respectively), while sensitivity and negative predictive values were 80.0 and 83.0% respectively. Depolarization analysis was particularly effective for Plasmodium falciparum malaria but there was lower detection sensitivity for White compared with Black African patients. CD4000 90 degrees depolarization vs 0 degrees analysis revealed a proportion of samples with small nonleucocyte-associated depolarizing particles. Appearance of such events in the form of a discrete cluster was associated with P. vivax rather than P. falciparum infection.     

Field trial of the RTM dipstick method for the rapid diagnosis of malaria based on the detection of Plasmodium falciparum HRP-2 antigen in whole blood

The performance of the Quorum RapidTest Malaria (RTM) dipstick method that detects Plasmodium falciparum histidine-rich protein-2 (PfHRP-2) antigen in whole blood was evaluated in a malaria endemic area. Results were compared with conventional Giemsa-stained blood films. Of 306 people tested 37.9% (116/306) were found to be parasitaemic; of these 66.4% (77/116) were P. vivax and 32.8% (38/116) were P. falciparum infections. There was only one (0.9%) mixed P. falciparum plus P. vivax infection.The RTM test was positive in 35/36 patients with P. falciparum identified on blood smear examination, resulting in a sensitivity of 97.2% [95% confidence interval (CI): 91.6-102.8%]. Specificity was 96.3% (95% CI: 93.9-98.6%).The RTM test had a positive predictive value of 77.8% (95% CI: 65.7-89.9%) and a negative predictive value of 99.6% (95% CI: 98.4-100.8%). Of the 10 false positives, seven reported recent malaria episode and treatment, indicating persistence of antigenaemia. If these were assumed truly infected, the positive predictive value is increased to 93.3% (95% CI: 85.8-100.8%).The RTM test was positive in all seven P. falciparum infections with gametocytes and one mixed infection, but was negative in all falciparum gametocytes and relapsing fever cases. All but one P. vivax infection gave negative result on the RTM test.The RTM test missed one patient with parasitaemia. The test is highly sensitive and specific requiring no instrument or trained personnel. It appears to be a very useful tool for rapid diagnosis of malaria, especially in the rural health institutions with limited diagnostic facilities.     

Evaluation of four rapid diagnostic tests for the diagnosis of Plasmodium vivax in Korea

Objective To evaluate 4 rapid malaria diagnostic kits (RDTs) in Korea: OptiMAL test, SD BIOLINE Malaria Ag P.f/Pan test, Humasis Malaria P.f/Pan antigen test and CareStart? Malaria Pf/Pv Combo test. Methods Hundred malaria patients with Plasmodium vivax (P. vivax) and 100 healthy volunteers were recruited. The results from earlier four RDTs were compared with the reference standard, the Giemsa‐stained traditional microscopic diagnosis. Results Compared with the reference standard, the sensitivity and specificity for Plasmodium vivax were 92.7 and 100% for SD BIOLINE Malaria Ag P.f/Pan; and 94.6% and 100% for OptiMAL; 95.5% and 100% for both Humasis Malaria P.f/Pan antigen test and CareStart? Malaria Pf/Pv Combo test. Conclusion The performances of all four malaria RDT kits were acceptable, although Humasis Malaria P.f/Pan antigen test and CareStartTM Malaria Pf/Pv Combo test gave superior performances with ROK isolates.     

Evaluation of the ICT whole blood antigen card test to detect infection due to nocturnally periodic Wuchereria bancrofti in South India

The commercially available ICT Card Test for bancroftian filariasis was evaluated for its sensitivity and specificity in detecting microfilaria carriers among 189 individuals each in filariasis-endemic and nonendemic areas in South India, and compared to both conventional night blood finger prick thick blood smear examination and venous blood membrane filtration. Though the specificity of the test was 100% in comparison to both, the sensitivity was 98.5% against the finger prick thick blood smear and 71.9 compared to the membrane filtration technique. Similarly, the positive predictive value was 100% against both techniques, but the negative predictive values were 99.5% against the finger prick thick blood smear and 88.3% compared to the membrane filtration technique. The test's lower sensitivity compared to the filtration technique requires further investigation.     

镜检、抗原检测和核酸检测方法在疟疾诊断中的应用比较

目的 比较镜检、抗原检测(RDT)和核酸检测(PCR)三种方法对疟原虫的检测效果,为基层选择合适的 诊断方法提供依据。 方法 收集腾冲市 2015-2018 年发热病人的血样进行疟疾检测,以确诊结果为标准,对比分析镜检、RDT 和 PCR 三种疟疾检测方法的敏感性、特异性、阳性预测值、阴性预测值等指标。 结果 610 份血样中,阴性 295 份,阳性 315 份,其中恶性疟 67 份、间日疟 245 份、混合感染 2 份、三日疟 1 份。 与确诊结果比较,镜检、RDT 和 PCR 的灵敏度分别为 95. 87%、94. 60%和 99. 37%,特异度均为 100%;假阴性率分别为 4. 13%、5. 40%和 0. 63%,阴性预 测值分别为 95. 78%、94. 55%和 99. 33%;假阳性率均为 0,阳性预测值均为 100%;三种方法与确诊结果的总符合率分别 为 97. 87%、97. 70%和 99. 67%,Kappa 检验结果显示均与确诊结果高度一致(P 均<0. 001);对单一虫种恶性疟的检测, 镜检、RDT 和 PCR 的符合率分别为 88. 06%、100%和 97. 01%;对其他三种疟原虫检测的符合率,分别为 97. 97%、 93. 9%和 100%。 结论 三种检测方法均具有较高的敏感性和特异性,但综合考虑当前防治工作实际,抗原检测(RDT) 更适宜在基层推广和使用。     

A retrospective review of malaria cases seen in a non-endemic area of South Africa

BACKGROUND: Malaria is a risk for travelers to endemic areas. We describe the diagnosis and treatment of malaria in Pretoria, a non-endemic area in South Africa. METHODS: Records of specimens submitted to the medical microbiology laboratory for malaria investigations over 3 years were reviewed with follow up of hospital records for positive specimens for clinical data. The laboratory performs malaria smears and uses HRP2-Ag testing for rapid diagnosis of Plasmodium falciparum. RESULTS: A total of 516 specimens were received, with a 211/516 (41%) malaria smear positive rate. The number of malaria positive specimens has been increasing overtime and this increase was statistically significant in children [p=0.005]. HRP2-Ag testing was done on 430 specimens with124/430 (29%) being positive, of which 10/124 (8%) were smear negative, giving 98% sensitivity. Hospital records for 198/211 (94%) smear positive cases showed that 190/198 (96%) of the patients had a travel history with 170/190 (71%) having traveled to Mozambique, a malaria endemic country. Most patients presented with uncomplicated malaria; the CFR was 4/198 (2%). Treatment mainly followed South African national guidelines. CONCLUSION: Imported malaria is increasingly being diagnosed in returning travelers, especially from Mozambique. Rapid antigen tests remain useful for the diagnosis of malaria in non-endemic areas.     

新型荧光光源吖啶橙染色和QBC技术快速诊断间日疟的现场评价

１９９２－１９９８年期间用新型荧光光源,薄血膜吖淀橙染色法和吖啶橙包被的毛细管法,分别在四川省筠连县和名山县疟疾流行区,对４２８人进行现场应用,其中１４５例采用ＡＯ法和ＱＢＣ技术同时检测,并用姬姆萨染色作对照。     

Utility of a Point-of-Care Malaria Rapid Diagnostic Test for Excluding Malaria as the Cause of Fever among HIV-Positive Adults in Rural Rakai, Uganda

We compared results of a malaria rapid diagnostic test (Binax Now^® Malaria, Binax-M, Inverness Medical Innovations, Inc., Waltham, MA) performed at rural mobile clinics in Uganda by clinicians evaluating febrile adult HIV patients to thick smear evaluated at a central laboratory by trained microscopists. Two hundred forty-six samples were analyzed, including 14 (5.7%) which were thick-smear positive for falciparum malaria. Sensitivity of Binax-M compared with thick smear was 85.7% (95% CI: 57.2–98.2), specificity 97.8% (95% CI: 94.9–99.3), positive and negative predictive values were 70.6% (95% CI: 44.0–89.7) and 99.1% (95% CI: 96.8–99.9), respectively. The rapid diagnostic test accurately ruled malaria “in or out” at the point-of-care, facilitating appropriate clinical management and averting unnecessary anti-malarial therapy.     

Automated detection of malaria‐associated intraleucocytic haemozoin by Cell‐Dyn CD4000 depolarization analysis

Summary Laboratory tests for malaria are only performed if there is clinical suspicion of the disease, and a missed diagnosis contributes substantially to morbidity and mortality. Malaria parasites produce haemozoin, which is able to depolarize light and this allows the automated detection of malaria during routine complete blood count analysis (CBC) with some Abbott Cell‐Dyn instruments. In this study, we evaluated the Cell‐Dyn CD4000 with 831 blood samples submitted for malaria investigations. Samples were categorized as malaria negative (n = 417), convalescent malaria (n = 64) or malaria positive (n = 350) by reference to thin/thick film microscopy, ‘rapid test’ procedures, polymerase chain reaction analysis and clinical history. With regard to CD4000 depolarization analysis, a malaria positive CD4000 pattern was ascribed to samples that showed one or more abnormal depolarizing purple events, which corresponded to monocytes containing ingested malaria pigment (haemozoin). Positive CD4000 patterns were observed in 11 of 417, 50 of 64 and 281 of 350 of malaria negative, convalescent malaria and malaria positive samples respectively. The specificity and positive predictive values for malaria (active and convalescent) were very high (97.4 and 96.8%, respectively), while sensitivity and negative predictive values were 80.0 and 83.0% respectively. Depolarization analysis was particularly effective for Plasmodium falciparum malaria but there was lower detection sensitivity for White compared with Black African patients. CD4000 90° depolarization vs 0° analysis revealed a proportion of samples with small nonleucocyte‐associated depolarizing particles. Appearance of such events in the form of a discrete cluster was associated with P. vivax rather than P. falciparum infection.     

Clinical diagnosis of malaria: can we improve?

Most cases of malaria in Zimbabwe are diagnosed on the basis of clinical suspicion, without laboratory tests. Of patients treated, between 10 and 30% have malaria parasites on blood slide examination. Can diagnosis be improved by a systematic history? We examined this question in 287 patients treated for malaria in an area of year-round transmission in Zimbabwe. The most common complaints were 'headache' (85.7%), 'bodily weakness' (79.0%) and 'fever/feeling hot' (73.2%). Eighty patients (28%) had malaria parasites on blood smear. Using the blood slide as the standard, we calculated the sensitivity, specificity and positive predictive value of a variety of clinical symptoms and signs. None had a positive predictive value substantially higher than the unknown diagnostic criteria used by health workers (28%). Multivariate analysis showed that 15 different demographic and clinical variables did not significantly predict a positive blood slide result. We conclude that, in this setting, clinical history alone will not improve the diagnosis of malaria.     

Diagnosing non-gonococcal urethritis: the gram-stained urethral smear in perspective

The value of microscopy of a Gram-stained urethral smear in the diagnosis of non-gonococcal urethritis and chlamydial urethral infection was assessed in 153 men attending a department of genitourinary medicine. A mean of more than 4 polymorphs in 5 fields (x1000) was considered to be abnormal. In the diagnosis of urethritis, the sensitivity (94%), specificity (91%), positive predictive value (93%) and negative predictive value (93%) were high. In the diagnosis of chlamydial infection, sensitivity (91%) and negative predictive value (96%) were high, but specificity (68%) and positive predictive value (46%) were low. In men with symptoms of genitourinary infection, the sensitivity (96.7%) and negative predictive value (97.4%) of the Gram-stained urethral smear in the diagnosis of chlamydial infection was comparable with modern chlamydial antigen detection tests.     

Recent approach for diagnosis of early HCV infection

Detection of HCV infection during the window phase of infection, before seroconversion, is important in blood screening. However, a significant delay exists between the time of infection and the development of antibodies. The delay in window period can last up to 70 days. The aim of the present study was to investigate the kinetics of HCV markers during early infection, with detection of HCV core antigen as an early method for diagnosis. The study included determination of HCV RNA by qualitative and quantitative PCR, HCV core antigen detection by enzyme linked immunosorbent assay (ELISA) and specific serological markers including anti-HCV IgG and IgM. The study was carried out on 34 patients diagnosed as non A non B acute hepatitis and proved to be hepatitis C by qualitative HCV RNA PCR. Sixteen healthy control subjects were also included. From each consenting patient and control, blood samples were collected and serum was separated and subjected to determination of AST and ALT and the following virological laboratory tests: HCV core antigen detection by ELISA, determination of specific anti-HCV IgM and specific anti-HCV IgG, qualitative and quantitative determination of HCV RNA by second version of PCR. In patients, the median quantity of HCV RNA was 739.1 x 10(3) lu/ml with minimum quantity 2.1 x 10(3) lu/ml and maximum 38352.3 x 10(3) lu/ml. A comparison between the different diagnostic methods revealed that the highest sensitivity was for HCV-core antigen detection (82.4%), specificity was 100% negative predictive value was 72.2% and positive predictive value was 100%. Specific anti-HCV IgG had moderate levels of sensitivity (58.5%), specificity (75%), negative predictive value (46.2%)and positive predictive value (83.3%). The least sensitive method was the specific anti-HCV IgM (29.4%) with negative predictive value 40% but had specificity and positive predictive value of 100% of each. From this study we could conclude the followings: From virological methods, serological detection of specific IgM anti-HCV had the least sensitivity limits, while it had the highest specificity and positive predictive value. Specific anti-HCV IgG had moderate sensitivity and specificity. The most sensitive and specific tool for diagnosis of early HCV viraemia was the detection of HCV core Ag by ELISA when compared to molecular biological methods.     

Assessing the Performance of CareStart Malaria Pf/Pv Combo Test Against Thick Blood Film in the Diagnosis of Malaria in Northwest Ethiopia

Bivalent rapid diagnostic tests are promising diagnostic tools for Plasmodium falciparum and P. vivax. Their diagnostic performance was evaluated against thick blood smear to assist national malaria control programs. A cross-sectional study was conducted to evaluate the performance of CareStart against thick blood smears among 398 acute febrile patients visiting the Felegeselam Health Center in December of 2011. Thick blood smears were examined under 100× objectives to diagnose Plasmodium species. Similarly, CareStart Malaria Pf/Pv Combo Test was performed as per the manufacturer''s instruction. The ability of CareStart Malaria Pf/Pv Combo Test to diagnose Plasmodium malaria was very good, with 99.8% (95% confidence interval = 97.7–100%) sensitivity and 97.7% (95% confidence interval = 94.6–99.1%) specificity. The sensitivity and specificity of the CareStart Test is comparable with the thick blood smear in diagnosing malaria. Hence, it is preferable to use the CareStart Malaria Pf/Pv Combo Test instead of microscopy in areas where microscopic diagnosis is limited.