Detection Of Plasmodium Falciparum Infection Research Articles

Diagnostic performance of ultrasensitive rapid diagnostic test for the detection of Plasmodium falciparum infections in asymptomatic individuals in Kisangani, Northeast Democratic Republic of Congo

BackgroundUltrasensitive rapid diagnostic test (usRDT) was recently developed to improve the detection of low-density Plasmodium falciparum infections. However, its diagnostic performance has not been evaluated in the Democratic Republic of Congo (DRC). This study aims to determine the performance of the usRDT in malaria diagnosis in asymptomatic individuals under field condition in Kisangani, Northeast of DRC.MethodsA community-based cross-sectional study was carried out from June to August 2022 on 312 asymptomatic individuals residing in the city of Kisangani. Capillary blood samples were collected by finger prick for microscopic examination of thick and thin blood film, RDTs, and nested polymerase chain reaction (PCR). Alere™ Malaria Ag P.f usRDT and conventional RDT (cRDT/SD Bioline Malaria Ag P.f) kits were used for the detection of Plasmodium histidine rich protein 2 (HRP2) antigen as a proxy for the presence of P. falciparum. The diagnostic performance of the usRDT was compared with cRDT, microscopy and PCR.ResultsThe prevalence of asymptomatic P. falciparum malaria was 40.4%, 42.0%, 47.1% and 54.2% by cRDT, microscopy, usRDT and PCR, respectively. By using PCR as a reference, usRDT had sensitivity and specificity of 87.0% (95% CI 81.4–91.7) and 100.0% (95% CI 97.5–100.0), respectively, whereas the cRDT had sensitivity and specificity of 74.6% (95% CI 67.3–80.9) and 100% (95% CI 97.1–100.0), respectively. By using microscopy as a reference, usRDT had sensitivity and specificity of 96.9% (95% CI 92.4–99.2) and 89.0% (95% CI 83.5–93.1), respectively, while the cRDT had sensitivity and specificity of 96.2% (95% CI 92.3–98.7) and 100% (95% CI 97.9–100.0), respectively.ConclusionThe usRDT showed better diagnostic performance with higher sensitivity than the cRDT which is currently in use as point-of-care test. Further research is necessary to assess the access and cost-effectiveness of the usRDTs to use for malaria surveillance.

Rapid, sensitive, and convenient detection of Plasmodium falciparum infection based on CRISPR and its application in detection of asymptomatic infection

Rapid and convenient detection of the Plasmodium in clinically diagnosed individuals and asymptomatically infected populations is essential for global malaria eradication, especially in malaria-endemic African countries where medical equipment and professionals are relatively deficient. Here, we described a CRISPR-based diagnostic for the detection of Plasmodium falciparum, the deadliest and most prevalent species of malaria parasite in Africa, via lateral flow strip readout without the need of nucleic acid extraction. The assay exhibited 100% sensitivity on clinical samples (5 P falciparum) and significant consistency with qPCR test on asymptomatic infection samples (49 P falciparum and 51 non-P. falciparum, Kappa=0.839). An artemisinin-resistant P. falciparum strain and 4 other laboratory-cultured strains can also be detected through this assay, whereas no cross-reactivity with Plasmodium vivax was observed. A 0.001% parasitaemia (corresponding to ∼60 parasites/μL) below the “low parasite density” test threshold (200 parasites/µL) is detectable. Our study demonstrated that direct malaria detection using whole blood on the spot and the detection of both clinical and asymptomatic infections of P. falciparum are feasible. This method is expected to be employed for clinical testing and large-scale community screening in Africa and possibly other places, contributing to the accurate diagnosis and control of malaria.

Evaluation of the detection of Plasmodium falciparum infection in Urine, Plasma, Serum, and Dried Blood Spots using real-time Polymerase Chain React

Access to timely and accurate diagnostic tests has a significant impact on the management of malaria disease which is a global concern. Polymerase chain reaction (PCR) detection of Plasmodium DNA is highly sensitive in diagnosing malaria. The specimen of choice for this assay has been whole blood samples from patients with malaria caused by Plasmodium species. Nucleic acids can also be detected in urine, serum, plasma, and Dried Blood Spots (DBS) samples but there are few studies describing the diagnostic performance of PCR. Therefore, this study was aimed at evaluating the performance of realtime PCR (qPCR) in detecting malaria parasite DNA in serum, plasma, urine, and DBS. A cross-sectional study was conducted among 146 patients that attended the clinic at Bayeku, Oreta, Imota, Ijede, Agura Primary Health Centres (PHC) and Ikorodu General hospital of Lagos State. Urine samples and a total of 5 ml of blood were collected from each participant and made into dried blot spots, plasma, and serum. The samples were screened and assayed for Plasmodium falciparum by microscopy and Multiplex qPCR respectively. The sensitivity of qPCR using plasma, serum and urine specimens were 100%, 87%, and 52.6% respectively, while the specificity was 82%, 87.5% and 80% respectively. Parasite detection by microscopy showed greater agreement with detection by qPCR in serum (79.4%) than qPCR from plasma (75%) or urine (58.3%). In conclusion, malaria detection using qPCR assay on plasma has high sensitivity and can be used as an alternative to microscopy.

Plasmodium falciparum infection coinciding with the malaria vaccine candidate BK-SE36 administration interferes with the immune responses in Burkinabe children.

A vaccine targeting the erythrocyte stages of Plasmodium falciparum could play a role in preventing clinical disease. BK-SE36 is a promising malaria vaccine candidate that has shown a good safety profile and immunological responses during field evaluations. It was observed that repeated natural infections could result in immune tolerance against SE36 molecule. The primary trial was conducted to assess the safety and immunogenicity of the BK-SE36 in two cohorts of children aged 25-60 months (Cohort 1) and 12-24 months (Cohort 2). Immunization was at full dose (1.0 mL) administered at 0, 1, and 6 months. Blood samples were collected before each vaccination for immunological assessments and detection of Plasmodium falciparum infection by microscopy. Blood samples were further collected one month post each vaccination to evaluate immunogenicity. Of seventy-two (72) subjects that have received BK-SE36 vaccination, 71 had available blood smears during vaccination days. One month post Dose 2, the geometric mean of SE36 antibodies was 263.2 (95% CI: 178.9-387.1) in uninfected individuals compared to 77.1 (95% CI: 47.3-125.7) in infected participants. The same trend was observed one-month post booster dose. Participants uninfected at the time of booster vaccination had significantly higher GMTs compared to those who were infected (424.1 (95% CI: 301.9-595.8) vs. 92.8 (95% CI: 34.9-246.6), p = 0.002. There was a 14.3 (95% CI: 9.7-21.1) and 2.4 (95% CI: 1.3-4.4) fold-change, respectively, in uninfected and infected participants between one-month post Dose 2 and booster. The difference was statistically significant (p < 0.001). Concomitant infection by P. falciparum during BK-SE36 vaccine candidate administration is associated with reduced humoral responses. However, it is to be noted that the BK-SE36 primary trial was not designed to investigate the influence of concomitant infection on vaccine-induced immune response and should be interpreted cautiously. WHO ICTRP, PACTR201411000934120.

Assessment of Plasmodium falciparum histidine rich protein 2 and /3 (pfhrp 2&/ pfhrp 3) gene deletion or mutation in Plasmodium falciparum positive blood samples in a tertiary care centre in South India.

Rapid diagnostic card tests (RDTs) enable timely and appropriate diagnosis of malaria especially in remote areas. Plasmodium falciparum histidine rich protein 2 (PFHRP2) is the most targeted antigen for the detection of Plasmodium falciparum infections by rapid diagnostic card test. Genetic mutations and gene deletions are important emerging factors for false-negative RDTs, which may delay the provision of life-saving treatment for the patients. Hence, we would like to evaluate for the existence of pfhrp2/3 gene deleted P. falciparum parasites in our health care setting. This study was conducted for a period of 2years in a tertiary care centre in South India. Blood samples that are microscopically confirmed as P. falciparum but negative by RDT were assessed for the presence of pfhrp2, pfhrp3, and their flanking genes using conventional PCR. Follow up of the clinical outcomes were also done for these patients. Of the 63 positive samples collected (50 /63) 79.4% were P.vivax and (13/63) 20.6% were P.falciparum by PCR. Among the 13 P. falciparum positive samples, 4 samples (4/13), (95% CI -10.36% to 61.11%) were found to be RDT negative but microscopically positive.Pfhrp2,pfhrp3 and their flanking genes were amplified for these 4 samples. All 4 samples were found to be negative for both pfhrp2-2 & pfhrp2-3 exon regions and also varying patterns of flanking gene deletions were also noted.This study provides molecular evidence for the existence of pfhrp2 & pfhrp3 deleted P. falciparum parasites in a tertiary care centre in South India warranting periodic evaluation of pfhrp2 based RDT use. Only pfhrp2/3 RDT based decision on diagnosis of P.falciparum malaria should always be reconsidered especially in remote areas.

Anopheles bionomics, insecticide resistance and malaria transmission in southwest Burkina Faso: A pre-intervention study.

BackgroundTwenty-seven villages were selected in southwest Burkina Faso to implement new vector control strategies in addition to long lasting insecticidal nets (LLINs) through a Randomized Controlled Trial (RCT). We conducted entomological surveys in the villages during the dry cold season (January 2017), dry hot season (March 2017) and rainy season (June 2017) to describe malaria vectors bionomics, insecticide resistance and transmission prior to this trial.MethodsWe carried out hourly catches (from 17:00 to 09:00) inside and outside 4 houses in each village using the Human Landing Catch technique. Mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Anopheles funestus group were identified using molecular techniques as well as detection of Plasmodium falciparum infection and insecticide resistance target-site mutations.ResultsEight Anopheles species were detected in the area. Anopheles funestus s.s was the main vector during the dry cold season. It was replaced by Anopheles coluzzii during the dry hot season whereas An. coluzzii and An. gambiae s.s. were the dominant species during the rainy season. Species composition of the Anopheles population varied significantly among seasons. All insecticide resistance mechanisms (kdr-w, kdr-e and ace-1 target site mutations) investigated were found in each members of the An. gambiae complex but at different frequencies. We observed early and late biting phenotypes in the main malaria vector species. Entomological inoculation rates were 2.61, 2.67 and 11.25 infected bites per human per month during dry cold season, dry hot season and rainy season, respectively.ConclusionThe entomological indicators of malaria transmission were high despite the universal coverage with LLINs. We detected early and late biting phenotypes in the main malaria vector species as well as physiological insecticide resistance mechanisms. These data will be used to evaluate the impact of complementary tools to LLINs in an upcoming RCT.

Diagnostic Performance of Malaria Rapid Diagnostic Test and Microscopy Compared with PCR for Detection of Plasmodium falciparum Infections among Primary Schoolchildren in Kibiti District, Eastern Tanzania: An Area with Moderate Malaria Transmission

A substantial decline of malaria transmission intensity has been observed in sub-Saharan Africa over the past two decades and may affect the diagnostic performance of malaria rapid diagnostic test (mRDT) and microscopy. Diagnostic performance of histidine-rich protein II (HRP-II)/pan-lactate dehydrogenase (pLDH)-based mRDT and microscopy was evaluated against polymerase chain reaction (PCR) for the diagnosis of Plasmodium falciparum infection among 316 primary schoolchildren in Kibiti district, in 2016. Polymerase chain reaction detected more cases of P. falciparum infection than mRDT or microscopy. Using PCR as reference, the sensitivity and specificity of mRDT were 75.9% (95% CI = 62.8-86.1) and 96.9% (95% CI = 94.0-98.7), respectively, whereas that of microscopy were 63.8% (95% CI = 50.1-76.0) and 95.7% (95% CI = 92.5-97.9), respectively. Polymerase chain reaction and other molecular methods should be considered for use in schools and other epidemiological surveys as supplement to mRDT or microscopy.

Deletions of pfhrp2 and pfhrp3 genes of Plasmodium falciparum from Honduras, Guatemala and Nicaragua

BackgroundMalaria remains a public health problem in some countries of Central America. Rapid diagnostic tests (RDTs) are one of the most useful tools to assist in the diagnosis of malaria in remote areas. Since its introduction, a wide variety of RDTs have been developed for the detection of different parasite antigens. PfHRP2 is the most targeted antigen for the detection of Plasmodium falciparum infections. Genetic mutations and gene deletions are important factors influencing or affecting the performance of rapid diagnostic tests.MethodsIn order to demonstrate the presence or absence of the pfhrp2 and pfhrp3 genes and their flanking regions, a total of 128 blood samples from patients with P. falciparum infection from three Central American countries were analysed through nested or semi-nested PCR approaches.ResultsIn total, 25.8 and 91.4% of the isolates lacked the region located between exon 1 and exon 2 of pfhrp2 and pfhrp3 genes, respectively. Parasites from the three countries showed deletions of one or both genes. The highest proportion of pfhrp2 deletions was found in Nicaragua while the isolates from Guatemala revealed the lowest number of pfhrp2 deletions. Parasites collected from Honduras showed the highest proportion of phfrp3 absence (96.2%). Twenty-one percent of isolates were double negative mutants for the exon 1–2 segment of both genes, and 6.3% of isolates lacked the full-length coding region of both genes.ConclusionsThis study provides molecular evidence of the existence of P. falciparum isolates lacking the pfhrp2 and pfhrp3 genes, and their flanking regions, in Honduras, Guatemala and Nicaragua. This finding could hinder progress in the control and elimination of malaria in Central America. Continuous evaluation of RDTs and molecular surveillance would be recommended.

Major aetiologies of acute undifferentiated fever in 2013 and 2014: an experience in retrospect

Background: Major aetiologies of acute undifferentiated fever (AUF) show wide variations, especially in developing countries including India. A better understanding of ‘AUF causes’ helps in better management of such cases with attendant reduction in morbidity and mortality. The present analytical study, retrospective in nature, estimates burden of the AUF in the years 2013 and 2014 with some useful information and conclusions.Methods: Important pathogens ‘investigated for’ either as a ‘direct or indirect evidence’ included - Malaria parasite, Dengue virus, Salmonella typhi and paratyphi A and Chikungunya virus. Malaria testing included examination of peripheral blood smear with Giemsa stain and also immuno-chromatographic test to detect lactate dehydrogenase (LDH) for Plasmodium falciparum and Plasmodium vivax and also HRP2 for detection of Plasmodium falciparum infections. For dengue and chikungunya virus infections - specific IgM antibodies - were detected by ELISA test. Enteric fever was diagnosed by detecting IgM and IgG antibodies using enzyme immunoassay. For Widal test, agglutinating antibodies against the O and H antigens of S. typhi and “H” antigens of ‘S. paratyphi A’ were undertaken. All the test procedures, including sample collections, were performed as per manufacturer’s recommendations, and, as per ‘standard operating procedures (SOPs)’.Results: Of the 10,670 samples received for dengue investigations, 3646 i.e. 34.17% tested seropositive for dengue cases. Percentage seropositivity for chikungunya was 18.6 (8/48). For dengue, 1193 (43.92%) and 488/577 (84.57%) samples were positive in the year 2013 and 2014 respectively in Delhi alone. Annual peak in months of September to November was observed for dengue while a bi-annual pattern was observed for malaria with two peaks occurring in months of May-June and August-September respectively for the year (s) i.e. 2013 and 2014. Enteric fever was present throughout the year with no specific distribution pattern. Majority of patients were from Delhi and adjoining Haryana followed by Western Uttar Pradesh. Co-infection of dengue with enteric fever was observed in only four cases.Conclusions: Dengue, chikungunya, malaria and enteric fever were the most important major causes of AUF in the year 2013 and 2014. Improved interactions with clinician counterparts generating awareness about major aetiologies of AUF would help in timely detection of such illnesses and hence better management reducing morbidity and mortality in the long run.

Insecticide-treated net effectiveness at preventing Plasmodium falciparum infection varies by age and season

BackgroundAfter increasing coverage of malaria interventions, malaria prevalence remains high in Malawi. Previous studies focus on the impact of malaria interventions among children under 5 years old. However, in Malawi, the prevalence of infection is highest in school-aged children (SAC), ages 5 to 15 years. This study examined the interaction between age group and insecticide-treated net (ITN) use for preventing individual and community-level infection in Malawi.MethodsSix cross-sectional surveys were conducted in the rainy and dry seasons in southern Malawi from 2012 to 2014. Data were collected on household ITN usage and demographics. Blood samples for detection of Plasmodium falciparum infection were obtained from all household members present and over 6 months of age. Generalized linear mixed models were used to account for clustering at the household and community level.ResultsThere were 17,538 observations from six surveys. The association between ITN use and infection varied by season in SAC, but not in other age groups. The adjusted odds ratio (OR) for infection comparing ITN users to non-users among SAC in the rainy season and dry season was 0.78 (95% CI 0.56, 1.10) and 0.51 (0.35, 0.74), respectively. The effect of ITN use did not differ between children under five and adults. Among all non-SACs the OR for infection was 0.78 (0.64, 0.95) in those who used ITNs compared to those that did not. Community net use did not protect against infection.ConclusionsProtection against infection with ITN use varies by age group and season. Individual estimates of protection are moderate and a community-level effect was not detected. Additional interventions to decrease malaria prevalence are needed in Malawi.

Field performance of malaria rapid diagnostic test for the detection of Plasmodium falciparum infection in Odisha State, India.

Background & objectives:Rapid diagnostic tests (RDTs) have become an essential surveillance tool in the malaria control programme in India. The current study aimed to assess the performance of ParaHIT-f, a rapid test in diagnosis of Plasmodium falciparum infection through detecting its specific antigen, histidine rich protein 2 (PfHRP-2), in Odisha State, India.Methods:The study was undertaken in eight falciparum malaria endemic southern districts of Odisha State. Febrile patients included through active case detection, were diagnosed by Accredited Social Health Activists (ASHAs) for P. falciparum infection using the RDT, ParaHIT-f. The performance of ParaHIT-f was evaluated using microscopy as the gold standard.Results:A total of 1030 febrile patients were screened by both microscopy and the RDT for P. falciparum infection. The sensitivity of ParaHIT-f was 63.6% (95% CI: 56.0-70.6) and specificity was 98.9% (95% CI: 97.9-99.5), with positive and negative predictive values (PPV and NPV) of 92.6% (95% CI: 86.0-96.3) and 93.0% (95% CI: 91.0-94.5), respectively. When related to parasitaemia, the RDT sensitivity was 47.8% at the low parasitaemia of 4 to 40 parasites/μl of blood.Interpretation & conclusions:The results showed that the performance of the RDT, ParaHIT-f, was not as sensitive as microscopy in detecting true falciparum infections; a high specificity presented a low frequency of false-positive RDT results. The sensitivity of ParaHIT-f was around 60 per cent. It is, therefore, essential to improve the efficiency (sensitivity) of the kit so that the true falciparum infections will not be missed especially in areas where P. falciparum has been the predominant species causing cerebral malaria.

Mosquito biting activity on humans &amp; detection of Plasmodium falciparum infection in Anopheles stephensi in Goa, India

Background & objectives:Knowledge of the bionomics of mosquitoes, especially of disease vectors, is essential to plan appropriate vector avoidance and control strategies. Information on biting activity of vectors during the night hours in different seasons is important for choosing personal protection measures. This study was carried out to find out the composition of mosquito fauna biting on humans and seasonal biting trends in Goa, India.Methods:Biting activities of all mosquitoes including vectors were studied from 1800 to 0600 h during 85 nights using human volunteers in 14 different localities of three distinct ecotypes in Goa. Seasonal biting trends of vector species were analysed and compared. Seasonal biting periodicity during different phases of night was also studied using William's mean.Results:A total of 4,191 mosquitoes of five genera and 23 species were collected. Ten species belonged to Anopheles, eight to Culex, three to Aedes and one each to Mansonia and Armigeres. Eleven vector species had human hosts, including malaria vectors Anopheles stephensi (1.3%), An. fluviatilis (1.8%), and An. culicifacies (0.76%); filariasis vectors Culex quinquefasciatus (40.8%) and Mansonia uniformis (1.8%); Japanese encephalitis vectors Cx. tritaeniorhynchus (17.4%), Cx. vishnui (7.7%), Cx. pseudovishnui (0.1%), and Cx. gelidus (2.4%); and dengue and chikungunya vectors Aedes albopictus (0.9%) and Ae. aegypti (0.6%). Two An. stephensi of the total 831 female anophelines, were found positive for P. falciparum sporozoites. The entomological inoculation rate (EIR) of P. falciparum was 18.1 and 2.35 for Panaji city and Goa, respectively.Interpretation & conclusions:Most of the mosquito vector species were collected in all seasons and throughout the scotophase. Biting rates of different vector species differed during different phases of night and seasons. Personal protection methods could be used to stop vector-host contact.

Microscopy Underestimates the Frequency of Plasmodium Falciparum Infection in Symptomatic Individuals in a Low Transmission Highland Area

In an area with unstable malaria transmission, detection of Plasmodium falciparum infection in 379 symptomatic individuals was assessed by microscopy and three polymerase chain reaction (PCR) methodologies. P. falciparum infection was detected in 25% of patients by microscopy, 37% by nested PCR, 41% by merozoite surface protein-2 (MSP-2) PCR, and 45% by a ligase detection reaction-fluorescent microsphere assay (LDR-FMA). Of the 64 individuals who were LDR-FMA positive, microscopy negative and did not receive treatment, 8 (12.5%) had persistent symptoms and returned for treatment. Malaria attributable fraction (MAF) in symptomatic individuals was 14.6% by microscopy (95% confidence interval [CI] = 6.6-21.8%) and 28.2% by nested PCR (95% CI = 17.9-37.2%). In this highland area, P. falciparum infection in symptomatic individuals is detected more frequently by PCR than microscopy, and most frequently by LDR-FMA. P. falciparum infection appears to resolve without treatment in most LDR-FMA-positive, microscopy-negative individuals, but is persistent in a subset of these individuals and requires treatment.

Comparison of PCR-based detection of Plasmodium falciparum infections based on single and multicopy genes

PCR-based assays are the most sensitive and specific methods to detect malaria parasites.This study compared the diagnostic accuracy of three PCR-based assays that do not only differ in their sequence target, but also in the number of copies of their target region, for the detection of Plasmodium falciparum in 401 individuals living in a malaria-endemic area in Nigeria. Compared to a composite reference generated from results of all the 3 PCR assays, the stevor gene amplification had a sensitivity of 100% (Kappa = 1; 95% CI = 1.000–1.000), 83% (Kappa = 0.718; 95% CI = 0.648–0.788) by SSUrRNA gene PCR and 71% (Kappa = 0.552; 95% CI = 0.478–0.627) by the msa-2 gene amplification.Results from this study indicate that the stevor gene amplification is the most sensitive technique for the detection of P. falciparum. This assay may be an important reference standard, especially when a confirmatory technique with high sensitivity and specificity is needed for ruling out P. falciparum infection.

Age-related differences in the detection ofPlasmodium falciparuminfection by PCR and microscopy, in an area of Kenya with holo-endemic malaria

(2005). Age-related differences in the detection of Plasmodium falciparum infection by PCR and microscopy, in an area of Kenya with holo-endemic malaria. Annals of Tropical Medicine & Parasitology: Vol. 99, No. 4, pp. 431-435.

Plasmodium falciparum: PCR detection and genotyping of isolates from peripheral, placenta), and cord blood of pregnant Malawian women and their infants

Polymerase chain reaction (PCR) is both a sensitive means of detecting malaria parasitaemia, and a simple tool for identifying genetic differences in parasites infecting human subjects. We compared PCR to microscopy in detection of Plasmodium falciparum infection in peripheral, placental and cord blood samples collected from 131 pregnant Malawian women and their infants in 1997–1999. Infections detected by species-specific PCR were genotyped at the merozoite surface protein 1 and 2 loci, and minimum numbers of infecting genotypes determined. PCR was of similar sensitivity to microscopy in detecting peripheral and placental infection, and placental blood PCR was 100% specific compared to placental histology. Cord blood parasitaemia was more frequently detected by PCR than microscopy, 20% versus 6%. Genotype numbers in peripheral blood (mean 2·36; range 1–5), placental blood (mean 2·41; range 1–6) and cord (mean 2·14; range 1–4) were similar. The frequency of detection of each allelic family did not differ between sites. Genotypes from different sites in each patient were compared. In 69% of women, genotypes were detected in peripheral blood and not placenta, or vice versa, suggesting possible differential sequestration of different parasite populations. Cord blood genotypes were usually a subset of those in peripheral and placental blood, but, in some cases, genotypes were found in cord blood that were absent from the mother. Transplacental infection before term, and clearance of maternal infection, is postulated.

The ParaSight ™-F rapid dipstick antigen capture assay for monitoring parasite clearance after drug treatment of Plasmodium falciparum malaria

Three methods for the detection of Plasmodium falciparum infection in peripheral blood were compared during antimalarial treatment and follow-up in 32 Burundian patients: dipstick antigen capture assay, standard (TBF) and prolonged thick blood film examination (PTBF) (3×5 min and 3×20 min examination respectively). Parasitaemia was determined daily by comparison with total white blood cell counts (determined by Coulter counter) until no parasite was detected on 2 consecutive days by PTBF. Cumulatively, 231 observations were made with each assay: 64 were negative and 167 positive by PTBF (59 had parasite counts ≤100/μL). Compared to PTBF, the sensitivities of TBF and the dipstick assay were 1 · 0 for parasite counts >100/μL and 0 · 458 and 0 · 966 respectively for counts ≤100/μL. Overall, the dipstick assay was significantly more sensitive (0 · 988 vs. 0 · 808; P < 0 · 001) but less specific ( P = 0 · 013) than TBF. The dipstick assay is of potential use for monitoring response to drug treatment and for detecting low parasitaemias.

Geographic differences in the sensitivity of a polymerase chain reaction for the detection of Plasmodium falciparum infection.

The amplification of target DNA by highly specific probes using the polymerase chain reaction (PCR) provides a highly sensitive and specific method for the detection of malaria infection. The use the of PCR in settings with varying endemicity within one survey area has not been investigated intensively. Therefore, a cross-sectional study was conducted in the districts of Kabarole and Bundibugyo in western Uganda using material from three villages with different epidemiologic situations regarding malaria and DNA primers for a PCR that had shown satisfactory sensitivity and specificity in previous trials. The sensitivity of the PCR varied significantly (P < 0.001) in the three survey villages (between 63.2% and 83.9% for the primer pair K1-14-1 and between 37.9% and 69.9% for the primer pair MSP-1) and was highly linked to geographic differences and social exchanges of the inhabitants with other areas of the district. According to the results of this investigation, it is advisable not to use a single primer pair in epidemiologic field studies for the detection of falciparum malaria. The use of combined primer pairs and the frequent confirmation of the results by microscopy are recommended.

Nested polymerase chain reaction for detection of Plasmodium falciparum infection in Malaysia

Nested polymerase chain reaction for detection of Plasmodium falciparum infection in Malaysia

Detection of Plasmodium Falciparum Infection in Human Patients: A Comparison of the DNA Probe Method to Microscopic Diagnosis

We have previously reported the isolation and testing of a DNA probe specific for the detection of Plasmodium falciparum. Field studies to compare the sensitivity and specificity of the DNA probe with that of light microscopy have been performed. In 2 studies in Thailand, 1,397 patients were tested. Microscope slides were prepared in a standard fashion and examined by clinical technicians and expert microscopists. The DNA probe method compares favorably in sensitivity with routine microscopy, detecting parasite densities as low as 40 parasites/microliters blood in the first study and, after modifications, 20-25 parasites/microliters blood in the second. Modifications included the elimination of salt from the lysis buffer, increasing the pH of the lysis buffer, and use of nylon based hybridization membranes instead of nitrocellulose. The DNA probe method offers the advantage of a standardized procedure that can be used in a batchwise fashion on a large number of samples.