Detection of haematoparasites using quantitative buffy coat analysis tubes

New metabolic signature for Chagas disease reveals sex steroid perturbation in humans and mice

The causative agent of Chagas disease (CD), Trypanosoma cruzi, claims thousands of lives each year. Current diagnostic tools are insufficient to ensure parasitological detection in chronically infected patients has been achieved. A host-derived metabolic signature able to distinguish CD patients from uninfected individuals and assess antiparasitic treatment efficiency is introduced. Serum samples were collected from chronic CD patients, prior to and three years after treatment, and subjected to untargeted metabolomics analysis against demographically matched CD-negative controls. Five metabolites were confirmed by high-resolution tandem mass spectrometry. Several database matches for sex steroids were significantly altered in CD patients. A murine experiment corroborated sex steroid perturbation in T. cruzi-infected mice, particularly in male animals. Proteomics analysis also found increased steroidogenesis in the testes of infected mice. Metabolic alterations identified in this study shed light on the pathogenesis and provide the basis for developing novel assays for the diagnosis and screening of CD patients.

Use of buffy coat thick films in detecting malaria parasites in patients with negative conventional thick films

OBJECTIVE

To determine the frequency of malaria parasite detection from the buffy coat blood films by using capillary tube in falciparum malaria patients with negative conventional thick films.

METHODS

Thirty six uncomplicated falciparum malaria patients confirmed by conventional thick and thin films were included in the study. The patients were treated with artemisinin combination therapy at Hospital for Tropical Diseases, Bangkok, Thailand for 28 day. Fingerpricks for conventional blood films were conducted every 6 hours until negative parasitemia, then daily fingerpricks for parasite checks were conducted until the patients were discharged from hospital. Blood samples were also concurrently collected in 3 heparinized capillary tubes at the same time of fingerpricks for conventional blood films when the prior parasitemia was negative on thin films and parasitemia was lower than 50 parasites/200 white blood cells by thick film. The first negative conventional thick films were compared with buffy coat thick films for parasite identification.

RESULTS

Out of 36 patients with thick films showing negative for asexual forms of parasites, buffy coat films could detect remaining 10 patients (27.8%) with asexual forms of Plasmodium falciparum.

CONCLUSIONS

The study shows that buffy coat thick films are useful and can detect malarial parasites in 27.8% of patients whose conventional thick films show negative parasitemia.

Passive gravitational sedimentation of peripheral blood increases the sensitivity of microscopic detection of malaria

OBJECTIVE

To determine if passive gravitational sedimentation of blood samples, followed by buffy coat thin smear preparation could increase the sensitivity of malaria diagnosis when compared to conventional thin smear preparation without the additional cost of centrifuges or molecular diagnostics.

METHODS

Blood samples were collected from 205 patients. Each patient sample was analyzed using all three methods of sample preparation.

RESULTS

Buffy coat analysis of centrifuged blood samples greatly increased the sensitivity of malaria diagnosis when compared to standard thin smear techniques. Sensitivity between mechanically centrifuged samples and gravitationally sedimented samples showed equal improvement in sensitivity when compared to standard thin smear preparation.

CONCLUSIONS

Passive gravitational sedimentation of red blood cells followed by buffy coat analysis dramatically improves the sensitivity of malaria diagnosis without the additional costs associated with centrifugation.

Abnormal WBC scattergram: a clue to the diagnosis of malaria

OBJECTIVE

Malaria is highly prevalent and endemic in tropical countries and carries a significant health burden. The detection of malaria by light microscopy of Giemsa-stained smears is the gold standard. There are many hematological abnormalities associated with malaria like anemia, thrombocytopenia, and leucopenia; however, none of these abnormalities are specific. The present study was undertaken to assess the utility of WBC scattergram in predicting the diagnosis of malaria.

METHODS

In this study all cases diagnosed as Plasmodium vivax/Plasmodium falciparum infection on peripheral smear examination were included. Their complete blood counts and WBC scattergrams obtained from XT2000i were critically evaluated. Accordingly, sensitivity, specificity, positive predictive value (PPV), and negative predictive value of detection of malaria by abnormal WBC scattergram with and without abnormal blood counts were also calculated.

RESULTS

A total of 2251 ethylendiaminetetraacetic acid samples were run on XT2000i hematology autoanalyzer. Out of these 148 cases of malaria were diagnosed on peripheral smear (128 P. vivax and 20 P. falciparum). While analyzing the WBC scattergrams, 233 cases including 124 (83.8%) malaria cases showed different abnormalities. Sensitivity and PPV for the diagnosis of malaria by abnormal WBC scattergram were 83.78 and 53.20%, respectively. This had increased to 98.60 and 57.25%, respectively, when cytopenias were included.

DISCUSSION

Sysmex XT-2000i is capable of detecting specific abnormalities in WBC scattergram in patients with malaria. Therefore, the presence of an abnormal WBC scattergram with thrombocytopenia in a febrile patient helps the pathologist to clinch the diagnosis of malaria.

Comparative evaluation of real time PCR assay with conventional parasitological techniques for diagnosis of Trypanosoma evansi in cattle and buffaloes

For comparative evaluation, a real time PCR assay was standardized by using TaqMan primer and probe targeting the internal transcribed spacer 1 (ITS-1) region of rRNA for Trypanosoma evansi and sensitivity was evaluated by using DNA, extracted from diethyleamino ethane cellulose purified trypanosomes and trypanosomes infected whole blood of mice. The minimum detection limit for purified trypanosomal DNA was 0.01 ng (≈ 0.33 genomic DNA of T. evansi) whereas for whole blood the minimum detection limit was 0.1 ng (≈ 6.12 genomic DNA). T. evansi infected mice blood samples were collected at different interval post infection and were analysed by conventional parasitological methods (CPT) viz. wet blood smear, thin blood smear, thick blood smear, quantitative buffy coat and real time PCR and found that TaqMan assay was two fold sensitive than CPT in case of in vivo infectivity in mice and gave positive signal at 36 h post infection where as QBC and blood smear examination was able to detect at 60 h and 72 h post infection respectively. A total 109 (80 cattle and 29 buffaloes) blood samples were collected from in and around Ludhiana district and analysed by CPT and real time PCR. The overall prevalence of T. evansi by CPT in cattle and buffaloes was 2.75 per cent. The prevalence rate was 2.5 per cent in cattle and 3.45 per cent in buffaloes. By real time PCR overall prevalence was 12.84 per cent in cattle and buffaloes, with a prevalence rate of 12.50 per cent in cattle and 13.79 per cent in buffaloes.

Laboratory diagnosis of malaria in nonhuman primates

Nonhuman primates (NHPs) are commonly used for biomedical research because of the high level of gene homology that underlies physiologic similarity to human beings. Malaria parasites of the genus Plasmodium cause one of the most frequent parasitic diseases of NHPs originating from tropical and subtropical areas and as such represent a significant research confounder. Malaria in NHPs presents a diagnostic challenge especially to those laboratories that see no more than a few malaria cases per year in NHPs. The accurate and timely diagnosis of malaria infection in NHPs facilitates the appropriate treatment of individuals infected with the malaria parasites. Conventional microscopy based on the examination of Giemsa-stained thick and thin blood films remains the mainstay of laboratory diagnosis of malaria infection because of the high diagnostic sensitivity and specificity and also the capability for Plasmodium species identification and parasite counts. This procedure is recognized as technically difficult and time-consuming, requiring considerable training to obtain the necessary skills. In the past few years, efforts to replace the traditional but tedious reading of blood films have led to different techniques for the detection of malaria parasites, including fluorescence microscopy, detection of intraleukocytic hemozoin or malaria pigment using automated blood cell analyzers, immunochromatographic rapid diagnostic tests based on malaria antigen detection, and PCR assays. These techniques offer new approaches for diagnosing malaria in NHPs. This review focuses on the available laboratory diagnostic tools for malaria in NHPs.

Emerging trends in the diagnosis of Human African Trypanosomiasis

Human African trypanosomiasis (HAT) or sleeping sickness is caused by protozoan parasitesTrypanosoma brucei gambienseandT. b. rhodesiense. Despite the enormous technological progress in molecular parasitology in recent years, the diagnosis of HAT is still problematic due to the lack of specific tools. To date, there are two realities when it comes to HAT; the first one being the world of modern experimental laboratories, equipped with the latest state-of-the-art technology, and the second being the world of HAT diagnosis, where the latest semi-commercial test was introduced 30 years ago (Magnuset al.1978). Hence, it appears that the lack of progress in HAT diagnosis is not primarily due to a lack of scientific interest or a lack of research funds, but mainly results from the many obstacles encountered in the translation of basic research into field-applicable diagnostics. This review will provide an overview of current diagnostic methods and highlight specific difficulties in solving the shortcomings of these methods. Future perspectives for accurate, robust, affordable diagnostics will be discussed as well.

African trypanosomiasis and antibodies: implications for vaccination, therapy and diagnosis

African trypanosomiasis causes devastating effects on human populations and livestock herds in large parts of sub-Saharan Africa. Control of the disease is hampered by the lack of any efficient vaccination results in a field setting, and the severe side effects of current drug therapies. In addition, with the exception of Trypanosoma brucei gambiense infections, the diagnosis of trypanosomiasis has to rely on microscopic analysis of blood samples, as other specific tools are nonexistent. However, new developments in biotechnology, which include loop-mediated isothermal amplification as an adaptation to conventional PCR, as well as the antibody engineering that has allowed the development of Nanobody technology, offer new perspectives in both the detection and treatment of trypanosomiasis. In addition, recent data on parasite-induced B-cell memory destruction offer new insights into mechanisms of vaccine failure, and should lead us towards new strategies to overcome trypanosome defenses operating against the host immune system.

Application of molecular methods for monitoring transmission stages of malaria parasites

Recent technical advances in malaria research have allowed specific detection of mRNA of genes that are expressed exclusively in sexual stages (gametocytes) of malaria parasites. The specificity and sensitivity of these techniques were validated on cultured laboratory clones of both human malaria parasites (Plasmodium falciparum) and rodent parasites (P. chabaudi). More recently, quantitative molecular techniques have been developed to quantify these sexual stages and used to monitor gametocyte dynamics and their transmission to mosquitoes. Molecular techniques showed that the infectious reservoir for malaria is larger than expected from previous microscopic studies; individual parasite genotypes within an infection can simultaneously produce infectious gametocytes; gametocyte production can be sustained for several months, and is modulated by environmental factors. The above techniques have empowered approaches for in-depth analysis of the biology of the transmission stages of the parasite and epidemiology of malaria transmission.

Options for field diagnosis of human african trypanosomiasis

Human African trypanosomiasis (HAT) due to Trypanosoma brucei gambiense or T. b. rhodesiense remains highly prevalent in several rural areas of sub-Saharan Africa and is lethal if left untreated. Therefore, accurate tools are absolutely required for field diagnosis. For T. b. gambiense HAT, highly sensitive tests are available for serological screening but the sensitivity of parasitological confirmatory tests remains insufficient and needs to be improved. Screening for T. b. rhodesiense infection still relies on clinical features in the absence of serological tests available for field use. Ongoing research is opening perspectives for a new generation of field diagnostics. Also essential for both forms of HAT is accurate determination of the disease stage because of the high toxicity of melarsoprol, the drug most widely used during the neurological stage of the illness. Recent studies have confirmed the high accuracy of raised immunoglobulin M levels in the cerebrospinal fluid for the staging of T. b. gambiense HAT, and a promising simple assay (LATEX/IgM) is being tested in the field. Apart from the urgent need for better tools for the field diagnosis of this neglected disease, improved access to diagnosis and treatment for the population at risk remains the greatest challenge for the coming years.

Comparative assessment of conventional PCR with multiplex real-time PCR using SYBR Green I detection for the molecular diagnosis of imported malaria

For the diagnosis of imported malaria, optical or immunochromatographic methods are known to be less sensitive and less specific than PCR-based methods, which are conversely more complicated and time-consuming. An original strategy, based upon the sequential use of a multiplex competitive real-time PCR detecting Plasmodium falciparum or Plasmodium spp. infection, followed by, if necessary, a single real-time PCR for species identification, was therefore performed and then tested versus conventional PCR in routine conditions. Conventional PCR has been used since October 1999 in the Department of Parasitology, University Hospitals in Toulouse, as a 2nd line diagnostic method. Out of 183 patients tested, 48 were found to be harbouring a falciparum infection by conventional microscopy, 60 by conventional PCR and 60 by multiplex competitive real-time PCR. Nine further patients had a non-falciparum infection, and concordant species identifications were obtained by both conventional PCR and single real-time PCR. The major value of PCR-based methods, when compared to microscopical techniques, was to ascertain the negativity of a suspect sample. Moreover, real-time PCR allows simplification of the operating procedure, with a diagnosis being made within 2 h.

Automated malaria diagnosis using pigment detection

Several new methods of malaria diagnosis have recently been developed, but these all rely on clinical suspicion and, consequently, an explicit clinical request. Although some methods lend themselves to automation (eg. PCR), no technique can yet be used for routine clinical automated screening. Detection of birefringent haemozoin has been used to diagnose malaria since the turn of the 20th century. A new generation of full blood count analysers, used widely in clinical laboratories, have the potential to detect haemozoin in white blood cells and probably erythrocytes. Thomas Hänscheid, Emilia Valadas and Martin Grobusch here describe this novel technique for malaria diagnosis and discuss its potential applications.

Hyperexpression of ICAM-1 and CD36 in placentas infected with Plasmodium falciparum: a possible role of these molecules in sequestration of infected red blood cells in placentas

AIMS

During pregnancy, Plasmodium falciparum malaria is frequent and associated with maternofetal complications. This could be the consequence of sequestration by several adhesion molecules of parasite-infected red blood cells in syncytiotrophoblast. To investigate the expression of ICAM-1 and CD36, two of the adhesion molecules for Plasmodium falciparum, an immunohistochemical study was carried out in malaria-infected placentas.

METHODS AND RESULTS

Thirty-five infected and 35 noninfected samples were chosen randomly. According to the histological classification of Bulmer, the infected placentas were separated in three groups: active, active chronic and past-chronic infection. CD36 was localized in the cytoplasm of stromal cells of terminal villi of infected or noninfected placentas, but not in syncytiotrophoblast. ICAM-1 was detected in the cytoplasm of stromal and endothelial villous cells in both infected and noninfected placentas and in syncytiotrophoblast of eight infected placentas showing more frequently active than active chronic or past-chronic infection (P < 0.001). The percentage of cells immunostained for CD36 or ICAM-1 was evaluated in the terminal villi. The proportion of villous cells, with ICAM-1 and CD36 immunostaining, was significantly higher in infected vs. noninfected placentas (P < 0.0001) and CD36 was detected more in acute inflammatory vs. past-chronic inflammatory placentas (P < 0.05).

CONCLUSIONS

The higher expression of ICAM-1 in infected placentas and its localization in syncytiotrophoblast particularly during acute infection, suggest ICAM-1 can act directly in the sequestration of parasite-infected red blood cells (IRBCs). On the other hand, the expression of CD36 is influenced by the presence of IRBCs without being directly implicated in sequestration of IRBCs. The hyperexpression of these two molecules could explain the high frequency of malaria during pregnancy.

Diagnosis of malaria: a review of alternatives to conventional microscopy

Malaria causes significant morbidity and mortality worldwide, including countries with mainly imported malaria. In developing nations, scarce resources lead to inadequate diagnostic procedures. In affluent countries, poor familiarity with malaria may cause clinical and laboratory misdiagnosis. Microscopy of Giemsa-stained thick and thin films remains the current standard for diagnosis. Although it has good sensitivity and allows species identification and parasite counts, it is time consuming, requires microscopical expertise and maintenance of equipment. Microscopy with fluorescent stains (QBC), dipstick antigen detection of HRP2 and pLDH (Parasight-F, ICT Malaria Pf, OptiMAL), polymerase chain reaction assays and some automated blood cell analysers offer new approaches and are reviewed here, with emphasis on clinical relevance and their potential to complement conventional microscopy, especially in countries with imported malaria.

Quantitative computer image analysis of chondroitin sulfate A expression in placentas infected with Plasmodium falciparum

Most pathological conditions resulting from infection with the human malaria parasite Plasmodium falciparum occur as a consequence of the sequestration by several adhesion molecules of parasite-infected red blood cells (IRBCs). Recent reports have provided evidence that placental vascular endothelial ligands for IRBCs were mostly restricted to chondroitin sulfate A (CSA). The expression of CSA in malaria-infected placentas was investigated in a prospective case-control study in a hypoendemic area (Dakar, Senegal). The tissue distribution of CSA was measured in the terminal villi by immunostaining combined with image processing in 20 infected and 20 noninfected frozen sections of placenta. The villous surface immunostained by anti-CSA antibody was higher in infected than in noninfected placentas (p<0.03), in placentas with active infection than in those with past chronic infection (p<0.05), and in infected placentas with positive imprints than in those with negative imprints (not significant; p=0.06). Labeling was found in the extracellular matrix and in endothelial and stromal cells of all the placentas. Syncytiotrophoblast immunostaining was detected in all placentas associated with active or active chronic infection (n=7) but in only 4/13 placentas with past chronic infection (p<0.01). The presence of P. falciparum in the imprint was significantly correlated with immunostaining of CSA in syncytiotrophoblasts (p=0.003). These results suggest that CSA can play an important role in the sequestration of P. falciparum in human placentas during the acute phase of infection.

[An attempt to detect Trypanosoma cruzi in the peripheral blood of patients with Chagas' disease, in chronic phase, using quantitative buffy coat (QBC)]

Taking for granted the sensitivity of the Quantitative Buffy Coat (QBC) system, as documented in a murine experimental model, we assayed to detect Trypanosoma cruzi in the peripheral blood of 100 patients with Chagas disease in its chronic phase. By means of the method, no positivity occurred, evently as a consequence of small parasitemias, undetectable by this technique as assessed by the cases in consideration.

Comparative evaluation of four techniques for the diagnosis of Plasmodium falciparum infections

Four diagnostic techniques for Plasmodium falciparum infection were evaluated against serial parasite dilutions and on identical field samples. These were (i) Giemsa-stained thick blood films (GTF), (ii) acridine orange-stained thick (AOTF) and thin (AOTnF) blood films, (iii) the quantitative buffy coat technique (QBC); and (iv) the ParaSight-F dipstick test (PS). PS had a consistently higher sensitivity and speed, was easiest to learn, and required no laboratory facility. The 100% sensitivity cut-off points against known parasite densities (per mm3) were: PS, 30; GTF, 84; QBC, 84; AOTnF, 84; AOTF, 149. In the field study, test sensitivities compared with examination of 800 microscope fields of a Giemsa-stained thin blood film were PS, 96.6%; AOTF, 93.1%; GTF, 91.4%; QBC, 89.7%; AOTnF, 82.8%. In the dilution study, one false positive result was recorded with QBC; in the field study there was one false positive each with PS, AOTnF and AOTF. When a newly trained microscopist examined samples of the parasite dilutions, the 100% sensitivity cut-off points were AOTF, 84; GTF, 140; QBC, 390. Total handling time was shortest with PS regardless of whether samples were processed individually or in batches of 10 or 100. The ParaSight-F test is recommended as the diagnostic tool for the future.

ACP Broadsheet no 148. July 1996. Laboratory diagnosis of malaria

Images

Diagnosis of malaria by acridine orange fluorescent microscopy in an endemic area of venezuela

Fluorescent (acridine orange) microscopical examination of capillary centrifuged blood (quantitative buffy coat [QBC] analysis) and Giemsa stained thick blood smears (GTS) were compared for diagnosis of malaria in blood specimens from adults living in malaria transmission areas of the States of Bolivar and Amazonas in southeastern and south Venezuela, respectively. Of a total of 198 GTS examined, 95 subjects (48%) showed parasitaemia. Among the 95 blood films with a positive GTS, 94 were judged positive by the QBC. However, positive QBC tubes were found in 29 out of 103 blood specimens with a negative GTS. Thus, relative to a GTS standard, the sensitivity and specificity of the QBC-test was 99.2% and 72%, respectively. Young trophozoites of Plasmodium vivax and P. falciparum could not be distinguished with certainty. It is confirmed that the QBC offers many advantages compared with the standard diagnosis of malaria parasites, specifically in the speed of staining and ease of interpretation. However, in places where P. falciparum and P. vivax occur, species and stage differentiation should be confirmed with the GTS.

Current state and future trends in the diagnosis of babesiosis

An overview is given of the currently available methods to diagnose babesiosis in livestock. Microscopic techniques are still the only appropriate techniques to diagnose acute disease. Thin or thick blood films stained with Giemsa's stain are sufficient. The sensitivity ranges from 10(-5) to 10(-6), i.e. one parasite per 10(5)-10(6) erythrocytes can be detected. Thick films stained with acridine orange (sensitivity approximately 10(-7)) and the Quantitative Buffy Coat (QBC) analysis tube system (sensitivity approximately 10(-7)-10(-8)) are applicable for diagnosis in the laboratory. DNA probes are very specific tools to identify haemoparasites in organs post mortem and in ticks. For the identification of carrier animals the sensitivity (approximately 10(-5)-10(-6)) is generally not sufficient. For the latter the polymerase chain reaction (PCR) technique is a very powerful tool (sensitivity approximately 10(-9)). Many different serodiagnostic tests have been described; however, the immunofluorescence antibody test is the most widely used, while the enzyme-linked immunosorbent assay (ELISA) is the test system which holds the greatest promise for the future. Thus far, improvements to the ELISA have been limited as the quality of antigen preparations made from infected blood is generally poor with a few exceptions (Babesia bovis, Babesia caballi). Potentially, most of the problems associated with crude antigens can be overcome by the production of recombinant antigens. Several ELISAs based on highly defined recombinant antigens have been described and show promise. None of these tests has been validated to the extent that it could be applied globally. Future research requirements as well as the need for coordination of the research effort and collaboration between institutions involved in the diagnosis of babesiosis are discussed.

The quantitative buffy coat for the diagnosis of trypanosomes

The use of quantitative buffy coat (QBC) tubes developed for malaria diagnosis is described in the diagnosis of African trypanosomiasis. One hundred and thirty-four patients with Trypanosoma gambiense were examined using QBC plus either haematocrit (HCT) or mini anion exchange centrifugation (MAEC) or both. QBC was the only method that detected all 134 patients. QBC proved to be the most sensitive diagnostic test for the detection of trypanosomes in blood. It is simple to use, gives fast results and would be a useful test at the district hospital level.

Immunomagnetic purification to facilitate DNA diagnosis of Plasmodium falciparum

The detection of pathogens by polymerase chain reaction (PCR) in clinical samples, such as blood, urine, or feces, requires initial sample preparation to remove polymerase inhibitors and to concentrate the target DNA. Here we show for the first time that immunomagnetic separation can be used to recover pathogens from whole blood and then used for PCR analysis. With antibodies to the merozoite surface protein (MSP1), the malaria-causing parasite Plasmodium falciparum was purified and concentrated from clinical samples. The recovered parasites were used directly for in vitro DNA amplification. The PCR product was subsequently analyzed by a colorimetric 96-well microtiter plate assay. The results from examining 117 patients attending a clinic in the Borai district, Thailand, demonstrate that the combined method with immunomagnetic separation followed by PCR increases the group of positively diagnosed patients compared with microscopic examination of stained blood films. Analysis of 1 microliter of whole blood resulted in a 12% (14 of 117) increase in positively diagnosed patients while a 10-microliters sample volume increased the positives diagnosed to 20.5% (24 of 117).

Avian trypanosomes as models of hemoflagellate evolution

In the 15 years since the last review on avian trypanosomes(1), there has been a steady accrual of information on the distribution and dynamics of trypanosome infections in wild bird populations. Recent immunological and biochemical studies provide evidence that several trypanosome species can parasitize an ecological guild of host species but the relative roles of avian host phylogeny and vector ecology remain unanswered. In this article, Victor Apanius reviews the habitat preferences and behavior of trypanosomes within the avian host and attempts to draw similarities in the strategy employed by the parasite for persistence in different vertebrate classes. Next, the question of host specificity is raised and recent evidence on the subject is examined with an eye toward understanding the distribution of trypanosome species in host communities.