Reliability of rapid diagnostic tests in diagnosing pregnancy-associated malaria in north-eastern Tanzania

Deep Machine Learning Model Trade-Offs for Malaria Elimination in Resource-Constrained Locations

The success of deep machine learning (DML) models in gaming and robotics has increased its trial in clinical and public healthcare solutions. In applying DML to healthcare problems, a special challenge of inadequate electrical energy and computing resources exists in regional and developing areas of the world. In this paper, we evaluate and report the computational and predictive performance design trade-offs for four candidate deep learning models that can be deployed for rapid malaria case finding. The goal is to maximise malaria detection accuracy while reducing computing resource and energy consumption. Based on our experimental results using a blood smear malaria test data set, the quantised versions of Basic Convolutional Neural Network (B-CNN) and MobileNetV2 have better malaria detection performance (up to 99% recall), lower memory usage (2MB 8-bit quantised model) and shorter inference time (33–95 microseconds on mobile phones) than VGG-19 fine-tuned and quantised models. Hence, we have implemented MobileNetV2 in our mobile application as it has even a lower memory requirement than B-CNN. This work will help to counter the negative effects of COVID-19 on the previous successes towards global malaria elimination.

Factors associated with sub-microscopic placental malaria and its association with adverse pregnancy outcomes among HIV-negative women in Dar es Salaam, Tanzania: a cohort study

BACKGROUND

Malaria infection during pregnancy has negative health consequences for both mothers and offspring. Sub-microscopic malaria infection during pregnancy is common in most African countries. We sought to identify factors associated with sub-microscopic placental malaria, and its association with adverse pregnancy outcomes among HIV-negative pregnant women in Dar es Salaam, Tanzania.

METHODS

We recruited a cohort of pregnant women during their first trimester and assessed for the occurrence of placental malaria and pregnancy outcomes. The follow-up was done monthly from recruitment until delivery. Histopathology placental malaria positive results were defined as the presence of malaria pigment or parasitized erythrocytes on the slide (histology-positive (HP)), and the sub-microscopic placental infection was defined as positive Plasmodium falciparum DNA by polymerase chain reaction (DNA PCR) amplification in a negative histopathology test. Adverse pregnancy outcomes investigated included low birth weight (birth weight below 2.5 kg), prematurity (live birth below 37 weeks), and small-for-gestational-age (SGA) (live born with a birth weight below 10th percentile for gestational age and sex). Weighted baseline category logit, log-binomial, and log-Poisson models were used to assess factors associated with placental malaria, and its association with adverse pregnancy outcomes.

RESULTS

Among 1115 women who had histopathology and DNA PCR performed, 93 (8%) had HP placental infection, and 136 (12%) had the sub-microscopic placental infection. The risk of sub-microscopic placental malaria was greater in women who did not use mosquito prevention methods such as bed nets, fumigation, or mosquito coils (odds ratio (OR) = 1.75; 95% confidence interval (CI): 1.05-2.92; P = 0.03) and in women who were anemic (OR = 1.59; 95% CI: 1.20-2.11; P = 0.001). Women who were underweight had reduced odds of sub-microscopic placental malaria infection (OR = 0.33; 95% CI: 0.17-0.62; P = 0.001). Women who were overweight/obese had 1.48 times higher the odds of HP placental malaria compared to normal weight (OR = 1.48; 95% CI: 1.03-2.11; P = 0.03). HP placental malaria infection was associated with an increased risk of SGA births (RR = 1.30, 95% CI: 0.98-1.72, P = 0.07). In contrast, the sub-microscopic infection was associated with a reduced risk of SGA births (RR = 0.61, 95% CI: 0.43-0.88, P = 0.01). Placental malaria was not associated with low birth weight or prematurity.

CONCLUSION

Malaria prevention methods and maternal nutrition status during early pregnancy were important predictors of sub-microscopic placental malaria. More research is needed to understand sub-microscopic placental malaria and the possible mechanisms mediating the association between placental malaria and SGA.

Malaria prevalence in symptomatic and asymptomatic pregnant women in a high malaria-burden state in India

Introduction

Malaria in pregnancy (‘MiP’) poses risks to mother, foetus and newborn. Studies from Africa and Asia have reported high prevalence of ‘MiP’ and recommended further research to address ‘MiP’. India has a significant burden of ‘MiP’ but most of the studies are a decade old. Hardly any studies exist in India that report on asymptomatic malaria in pregnant women. The current Indian policies for malaria control are silent on ‘MiP’. A campaign was carried out by community health workers (CHWs) in 2019 to screen pregnant women across rural Chhattisgarh.

Methods

This is a cross-sectional study. Malaria was tested in pregnant women by CHWs using bivalent rapid tests. Multi-stage sampling was used to cover 21,572 pregnant women screened across different geographical areas of rural Chhattisgarh. Cross-tabulation and multivariate regression were used to find out the relationship of ‘MiP’ with different symptoms and geographical areas. GIS maps were used to compare malaria in pregnant women against overall febrile population.

Results

In rural Chhattisgarh, malaria was present in 0.81% of the pregnant women at the time of testing. ‘MiP’ prevalence varied across geographies, reaching 4.48% in the geographical division with highest burden. Febrile pregnant women had three times greater malaria-positivity than overall febrile population and both showed a similar geographical pattern.

Discussion

Prevalence of ‘MiP’ was found to be less than earlier studies in the state. Though overall malaria in India has shown some decline, a policy response is needed for ‘MiP’ in high-burden areas. Fever, diarrhoea and jaundice remain relevant symptoms in ‘MiP’, but around one fourth of malaria-positive pregnant-women were afebrile, suggesting the need for strategies to address it.

Conclusion

The current study based on a large sample provides fresh evidence on ‘MiP’ in India. It used CHWs as skilled providers for large-scale screening for malaria. In high-burden areas, intermittent screening and treatment (IST) of all pregnant women can be a useful strategy in order to address ‘MiP’. Pregnant women can be considered as a pertinent sentinel population for malaria. The global and national policies need to evolve concrete strategies for addressing malaria in pregnancy.

Malaria preventive practices and delivery outcomes: A cross-sectional study of parturient women in a tertiary hospital in Eastern Uganda

BACKGROUND

Uganda ranks third in the number of deaths attributable to malaria and has some of the highest recorded malaria transmission rates in the general population. Malaria in Pregnancy is associated with detrimental effects for the mother and unborn baby and these effects seem to have long term effects and consequences on the life of the baby. Despite the preventive measures put in place by the World Health Organization in antenatal care, the burden of malaria in pregnancy is still high. We determined the use of malaria preventive strategies during pregnancy and the presence of plasmodium infection, anemia, and low birth weight babies at delivery among parturient women at Mbale regional referral hospital in eastern Uganda.

METHODS

A cross-sectional study was conducted among 210 women delivering at MRRH between July 2017 and January 2018. Information on demographics, antenatal care, and prevention practices was collected using an interviewer-administered questionnaire. Maternal venous blood and cord blood samples were screened for Plasmodium infection by both microscopy of Giemsa-stained blood films and Plasmodium falciparum rapid diagnostic test (pf. HPR2 mRDT). Polymerase Chain Reaction (PCR) was done on cord blood. The presence of anemia was determined by the use of an automated hemoglobin analyzer. Data were analyzed using descriptive and analytical statistics.

RESULTS

Of the 210 women, 3 (1.4%) and 19(9.1%) tested positive for malaria by using Giemsa stained blood smear microscopy and malaria rapid diagnosticMRDT tests respectively. PCR detected 4(%) of Plasmodium in cord blood. Twenty-nine percent of the women had anaemia and 11 (5.2%) had low birth weight babies. Only 23.3% of the women received at least three doses of IPTp-SP and 57.9% reported sleeping under an Insecticide Treated Net the night before the survey. The women who reported sleeping under a mosquito net the previous night (OR 0.67, 95% CI: 0.24-1.86) and those who reported taking fansidar as a directly observed therapy (OR 0.31, 95% CI: 0.04-2.39) appeared to have few chances of getting plasmodium infection though the findings were not statistically significant.

CONCLUSION

The effective use of malaria preventive strategies (IPT-SP and Insecticide Treated Nets) was generally low. Most of the women took less than three doses of SP and there was no strict adherence to the recommended directly observed therapy. The prevalence of Plasmodium infection during pregnancy was low though maternal anaemia and low birth weight were relatively high.

Malaria in Early Pregnancy and the Development of the Placental Vasculature

BACKGROUND

Pregnancy malaria has a negative impact on fetal outcome. It is uncertain whether infections in early pregnancy have a clinical impact by impeding the development of the placental vasculature.

METHODS

Tanzanian women (n = 138) were closely monitored during pregnancy. Placentas collected at birth were investigated using stereology to establish the characteristics of placental villi and vessels. Placental vasculature measures were compared between women infected with malaria and controls.

RESULTS

Compared with controls, placentas from women infected with malaria before a gestational age (GA) of 15 weeks had a decreased volume of transport villi (mean decrease [standard deviation], 12.45 [5.39] cm3; P = .02), an increased diffusion distance in diffusion vessels (mean increase, 3.33 [1.27] µm; P = .01), and a compensatory increase in diffusion vessel surface area (mean increase, 1.81 [0.74 m2]; P = .02). In women who had malaria before a GA of 15 weeks diffusion vessel surface area and transport vessel length distance were positive predictors for birth weight (multilinear regression: P = .007 and P = .055 for diffusion surface area and transport length, respectively) and GA at delivery (P = .005 and P = .04).

CONCLUSIONS

Malaria infection in early pregnancy impedes placental vascular development. The resulting phenotypic changes, which can be detected at delivery, are associated with birth weight and gestational length.

CLINICAL TRIALS REGISTRATION

NCT02191683.

Health workers' perception of malaria rapid diagnostic test and factors influencing compliance with test results in Ebonyi state, Nigeria

Background

The standard practice in treating uncomplicated malaria is to prescribe artemisinin-based combination therapy (ACT) for only patients with positive test results. However, health workers (HWs) sometimes prescribe ACTs for patients with negative malaria rapid diagnostic test (mRDT) results. Available evidence on HWs perception of mRDT and their level of compliance with test results in Nigeria lacks adequate stratification by state and context. We assessed HWs perception of mRDT and factors influencing ACTs prescription to patients with negative mRDT results in Ebonyi state, Nigeria.

Methods

A cross-sectional survey was conducted among 303 HWs who treat suspected malaria patients in 40 randomly selected public and private health facilities in Ebonyi state. Health workers’ perception of mRDT was assessed with 18 equally weighted five-point likert scale questions with maximum obtainable total score of 90. Scores ≥72 were graded as good and less, as poor perception. Data were analysed using descriptive statistics and logistic regression model at 5% significance level.

Results

Mean age of respondents was 34.6±9.4 years, 229 (75.6%) were females, 180 (59.4%) community health workers and 67 (22.1%) medical doctors. Overall, 114 (37.6%) respondents across healthcare facility strata had poor perception of mRDT. Respondents who prescribed ACTs to patients with negative mRDT results within six months preceding the survey were 154 (50.8%) [PHCs: 50 (42.4%), General hospitals: 18 (47.4%), tertiary facility: 51 (79.7%) and missionary hospitals: 35 (42.2%)]. Poor HWs’ perception of mRDT promoted prescription of ACT to patients with negative mRDT results (AOR = 5.6, 95% C.I = 3.2–9.9). The likelihood of prescribing ACTs to patients with negative mRDT results was higher among HWs in public health facilities (AOR = 2.8, 95% C.I = 1.4–5.5) than those in the private.

Conclusions

The poor perception of mRDT and especially common prescribing of ACTs to patients with negative mRDT results among HWs in Ebonyi state calls for context specific interventions to improve their perception and compliance with mRDT test results.

Anemia in late pregnancy induces an adaptive response in fetoplacental vascularization

INTRODUCTION

Anemia during pregnancy may compromise fetal and newborn's health, however, little is known about how and when the fetoplacental vascularization is most vulnerable to anemia.

METHODS

Using systematic and isotropic uniform random sampling, placental samples were collected from 189 placentas in a cohort study of Tanzanian women whose hemoglobin concentration was measured throughout pregnancy. Fetoplacental vessels and villi were defined as exerting either a transport or diffusion function. The vascularization patterns for transport and diffusion vessels and villi were assessed by stereology. Blood vessel length, surface area and diffusion distance as well as placental villi volume were calculated.

RESULTS

Anemia from a gestational age of 23 weeks was significantly associated with increased fetoplacental vascularization in vessels and villi compared to women who were non-anemic throughout pregnancy. Transport surface vessel area: 0.31 m² [95% CI: 0.18-0.55], P = 0.01; Transport villi volume 19.8 cm³ [95% CI: 6.37-33.2], P = 0.004, Transport vessel diameter 7.23 μm [95% CI: 1.23-13.3], P = 0.02. Diffusion vessel surface: 3.23 m² [95% CI: 1.55-4.91], P < 0.001 and diffusion villi volume: 29.8 cm³ [95% CI: 10.0-49.5], P = 0.003). Finally, all the measured transport vessel and villi significantly parameters and diffusion vessel surface, vessel diameter and diffusion distance were associated with birth weight.

DISCUSSION

Increased fetoplacental vascularization related to anemia from a gestational age of 23 weeks in pregnancy together with the association between fetoplacental vascularity and birth weight suggest that the timing of anemia determines the effect on fetoplacental vascularization and underlines the clinical relevance for proper development of fetoplacental vasculature.

Neutrophil alterations in pregnancy-associated malaria and induction of neutrophil chemotaxis by Plasmodium falciparum

Pregnancy-associated malaria (PAM) is a severe form of the disease caused by sequestration of Plasmodium falciparum-infected red blood cells (iRBCs) in the developing placenta. Pathogenesis of PAM is partially based on immunopathology, with frequent monocyte infiltration into the placenta. Neutrophils are abundant blood cells that are essential for immune defence but may also cause inflammatory pathology. Their role in PAM remains unclear. We analysed neutrophil alterations in the context of PAM to better understand their contribution to disease development. Pregnant women exposed to Plasmodium falciparum had decreased numbers of circulating neutrophils. Placental-like BeWo cells stimulated with malaria parasites produced the neutrophil chemoattractant IL-8 and recruited neutrophils in a trans-well assay. Finally, immunostaining of a PAM placenta confirmed neutrophil accumulation in the intervillous space. Our data indicate neutrophils may play a role in placental malaria and should be more closely examined as an etiological agent in the pathophysiology of disease.

The correlation between malaria RDT (Paracheck pf.®) faint test bands and microscopy in the diagnosis of malaria in Malawi

Background

Faint test bands of Paracheck Pf.® are interpreted as malaria positive according to world health organization (WHO) guideline. However if there are conspicuous number of faint test bands, a performance of Paracheck Pf.® could be influenced depending on whether interpreting faint test bands as malaria positive or negative. Finding out the frequency and accurate interpretation of faint test bands are important to prevent the overdiagnosis and drug resistance.

Methods

A cross-sectional, descriptive study was conducted to find out the frequency of faint test bands and evaluate the performance of Paracheck Pf.® by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of diagnosis of Paracheck Pf.® using microscopy as the gold standard. 388 suspected patients with malaria in Malawi were recruited in this study. Malaria rapid diagnostic tests (RDTs) and microscopy were used and patients’ information which includes age, sex, body temperature and signs or symptoms of malaria were recorded.

Results

Among all patients involved in the study, 29.1% (113/388) were found malaria positive by RDT. Overall 5.4% (21/388) of all Paracheck Pf.® tests resulted in a “faint test band” and 85.7% (18/21) corresponded with malaria negative by microscopy. Faint test bands which corresponded with malaria positive by microscopy were lower parasite density and there are no patients who showed definitive symptom of malaria, such as fever. When Paracheck Pf.® “faint test bands” were classified as positive, accuracy of diagnosis was 76.5% (95% CI 72%–80.7%) as compared to 80.4% (95% CI 76.1%–84.2%) when Paracheck Pf.® “faint test bands” were classified as negative.

Conclusions

This study shows that frequency of faint test bands is 5.4% in all malaria RDTs. The accuracy of diagnosis was improved when faint test bands were interpreted as malaria negative. However information and data obtained in this study may not be enough and more intensive research including a frequency and property of faint test bands is needed for significant interpretation of faint test bands.

Performance of pfHRP2 versus pLDH antigen rapid diagnostic tests for the detection of Plasmodium falciparum: a systematic review and meta-analysis

INTRODUCTION

There have been many inconsistent reports about the performance of histidine-rich protein 2 (HRP2) and lactate dehydrogenase (LDH) antigens as rapid diagnostic tests (RDTs) for the diagnosis of past Plasmodium falciparum infections. This meta-analysis was performed to determine the performance of pfHRP2 versus pLDH antigen RDTs in the detection of P. falciparum.

MATERIAL AND METHODS

After a systematic review of related studies, Meta-DiSc 1.4 software was used to calculate the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR). Forest plots and summary receiver operating characteristic curve (SROC) analysis were used to summarize the overall test performance.

RESULTS

Fourteen studies which met the inclusion criteria were included in the meta-analysis. The summary performances for pfHRP2- and pLDH-based tests in the diagnosis of P. falciparum infections were as follows: pooled sensitivity, 96.3% (95.8-96.7%) vs. 82.6% (81.7-83.5%); specificity, 86.1% (85.3-86.8%) vs. 95.9% (95.4-96.3%); diagnostic odds ratio (DOR), 243.31 (97.679-606.08) vs. 230.59 (114.98-462.42); and area under ROCs, 0.9822 versus 0.9849 (all p < 0.001).

CONCLUSIONS

The two RDTs performed satisfactorily for the diagnosis of P. falciparum, but the pLDH tests had higher specificity, whereas the pfHRP2 tests had better sensitivity. The pfHRP2 tests had slightly greater accuracy compared to the pLDH tests. A combination of both antigens might be a more reliable approach for the diagnosis of malaria.

Reliability of rapid diagnostic tests in diagnosing pregnancy and infant-associated malaria in Nigeria

BACKGROUND

The effective management of maternal and infant malaria requires rational and prompt diagnosis. This study aims to determine the diagnostic efficiency of malaria RDT in infants and pregnant women.

METHODS

The study was conducted on infants (n=200), pregnant women (n=80) and non-pregnant women (n=100) who were recruited from two hospitals in Lagos, Nigeria. Plasmodium falciparum infections were assessed in the febrile subjects by microscopic examinations of blood smears and by RDT.

RESULTS

The lowest (44.3%) and the highest (83.3%) sensitivity (SS) values were recorded in the infants and pregnant women, respectively. Other diagnostic parameters, including the specificity (SP, 97.5%), positive predictive value (PPV, 92.1%) and negative predictive value (NPV, 72.8%), in the infants were greater than the values recorded in non-pregnant (SP=77.5%, PPV=83.9%, NPV=70.5%) and pregnant women populations (SP=65.6%, PPV=78.4%, NPV=72.4%). The diagnostic efficiency of malaria RDT exhibited higher sensitivity in women in early gestational stages (1st trimester=78.6% and 2nd trimester=88.0%) compared with those in the 3rd trimester (71.4%). The sensitivity of malaria RDT (100.0%) was significantly higher in the multigravid women than in the primigravida (78.6%) and secundigravida women (77.8%, P<0.05). The sensitivity of the RDT significantly increased with the intensity of the malarial parasites (P<0.05).

CONCLUSION

Malaria is endemic in the study populations. Malaria RDT can serve as a first-line of diagnosis for pregnant women in early gestational stages and multigravid women and can aid the differential diagnoses of other diseases due to its high specificity in infants.

Performance of four HRP-2/pLDH combination rapid diagnostic tests and field microscopy as screening tests for malaria in pregnancy in Indonesia: a cross-sectional study

BACKGROUND

Malaria in pregnancy poses a major public health problem in Indonesia with an estimated six million pregnancies at risk of Plasmodium falciparum or Plasmodium vivax malaria annually. In 2010, Indonesia introduced a screen and treat policy for the control of malaria in pregnancy at first antenatal visit using microscopy or rapid diagnostic tests (RDTs). A diagnostic study was conducted in Sumba, Indonesia to compare the performance of four different RDTs in predominately asymptomatic pregnant women under field condition.

METHODS

Women were screened for malaria at antenatal visits using field microscopy and four HRP-2/pLDH combination RDTs (Carestart™, First-Response(®), Parascreen(®) and SD-Bioline(®)). The test results were compared with expert microscopy and nested PCR. End user experience of the RDTs in the field was assessed by questionnaire.

RESULTS

Overall 950 were recruited and 98.7 % were asymptomatic. The prevalence of malaria was 3.0-3.4 % by RDTs, and 3.6, 5.0 and 6.6 % by field microscopy, expert microscopy and PCR, respectively. The geometric-mean parasite density was low (P. falciparum = 418, P. vivax = 147 parasites/µL). Compared with PCR, the overall sensitivity of the RDTs and field microscopy to detect any species was 24.6-31.1 %; specificities were >98.4 %. Relative to PCR, First-Response(®) had the best diagnostic accuracy (any species): sensitivity = 31.1 %, specificity = 98.9 % and diagnostic odds ratio = 39.0 (DOR). The DOR values for Carestart™, Parascreen(®), SD-Bioline(®), and field microscopy were 23.4, 23.7, 23.5 and 29.2, respectively. The sensitivity of Pan-pLDH bands to detect PCR confirmed P. vivax mono-infection were 8.6-13.0 %. The sensitivity of the HRP-2 band alone to detect PCR confirmed P. falciparum was 10.3-17.9 %. Pan-pLDH detected P. falciparum cases undetected by the HRP-2 band resulting in a better test performance when both bands were combined. First Response(®) was preferred by end-users for the overall practicality.

CONCLUSION

The diagnostic accuracy to detect malaria among mostly asymptomatic pregnant women and perceived ease of use was slightly better with First-Response(®), but overall, differences between the four RDTs were small and performance comparable to field microscopy. Combination RDTs are a suitable alternative to field microscopy to screen for malaria in pregnancy in rural Indonesia. The clinical relevance of low density malaria infections detected by PCR, but undetected by RDTs or microscopy needs to be determined.

Rapid diagnostic tests for diagnosing uncomplicated non-falciparum or Plasmodium vivax malaria in endemic countries

BACKGROUND

In settings where both Plasmodium vivax and Plasmodium falciparum infection cause malaria, rapid diagnostic tests (RDTs) need to distinguish which species is causing the patients' symptoms, as different treatments are required. Older RDTs incorporated two test lines to distinguish malaria due to P. falciparum, from malaria due to any other Plasmodium species (non-falciparum). These RDTs can be classified according to which antibodies they use: Type 2 RDTs use HRP-2 (for P. falciparum) and aldolase (all species); Type 3 RDTs use HRP-2 (for P. falciparum) and pLDH (all species); Type 4 use pLDH (fromP. falciparum) and pLDH (all species).More recently, RDTs have been developed to distinguish P. vivax parasitaemia by utilizing a pLDH antibody specific to P. vivax.

OBJECTIVES

To assess the diagnostic accuracy of RDTs for detecting non-falciparum or P. vivax parasitaemia in people living in malaria-endemic areas who present to ambulatory healthcare facilities with symptoms suggestive of malaria, and to identify which types and brands of commercial test best detect non-falciparum and P. vivax malaria.

SEARCH METHODS

We undertook a comprehensive search of the following databases up to 31 December 2013: Cochrane Infectious Diseases Group Specialized Register; MEDLINE; EMBASE; MEDION; Science Citation Index; Web of Knowledge; African Index Medicus; LILACS; and IndMED.

SELECTION CRITERIA

Studies comparing RDTs with a reference standard (microscopy or polymerase chain reaction) in blood samples from a random or consecutive series of patients attending ambulatory health facilities with symptoms suggestive of malaria in non-falciparum endemic areas.

DATA COLLECTION AND ANALYSIS

For each study, two review authors independently extracted a standard set of data using a tailored data extraction form. We grouped comparisons by type of RDT (defined by the combinations of antibodies used), and combined in meta-analysis where appropriate. Average sensitivities and specificities are presented alongside 95% confidence intervals (95% CI).

MAIN RESULTS

We included 47 studies enrolling 22,862 participants. Patient characteristics, sampling methods and reference standard methods were poorly reported in most studies. RDTs detecting 'non-falciparum' parasitaemiaEleven studies evaluated Type 2 tests compared with microscopy, 25 evaluated Type 3 tests, and 11 evaluated Type 4 tests. In meta-analyses, average sensitivities and specificities were 78% (95% CI 73% to 82%) and 99% (95% CI 97% to 99%) for Type 2 tests, 78% (95% CI 69% to 84%) and 99% (95% CI 98% to 99%) for Type 3 tests, and 89% (95% CI 79% to 95%) and 98% (95% CI 97% to 99%) for Type 4 tests, respectively. Type 4 tests were more sensitive than both Type 2 (P = 0.01) and Type 3 tests (P = 0.03).Five studies compared Type 3 tests with PCR; in meta-analysis, the average sensitivity and specificity were 81% (95% CI 72% to 88%) and 99% (95% CI 97% to 99%) respectively. RDTs detecting P.vivax parasitaemiaEight studies compared pLDH tests to microscopy; the average sensitivity and specificity were 95% (95% CI 86% to 99%) and 99% (95% CI 99% to 100%), respectively.

AUTHORS' CONCLUSIONS

RDTs designed to detect P. vivax specifically, whether alone or as part of a mixed infection, appear to be more accurate than older tests designed to distinguish P. falciparum malaria from non-falciparum malaria. Compared to microscopy, these tests fail to detect around 5% ofP. vivax cases. This Cochrane Review, in combination with other published information about in vitro test performance and stability in the field, can assist policy-makers to choose between the available RDTs.

Asymptomatic Plasmodium falciparum infection is associated with anaemia in pregnancy and can be more cost-effectively detected by rapid diagnostic test than by microscopy in Kinshasa, Democratic Republic of the Congo

Background

In areas of high malaria transmission, Plasmodium falciparum infection during pregnancy is characterized by malaria-related anaemia, placental malaria and does not always result in clinical symptoms. This situation is associated with poor pregnancy outcomes. The aim of this study was to determine the extent of asymptomatic P. falciparum infection, its relation with anaemia as well as the most cost-effective technique for its diagnosis in healthy pregnant women living in Kinshasa, Democratic Republic of the Congo.

Methods

In a cross-sectional study design, information on socio-demographic characteristics and cost data were collected in healthy pregnant women attending antenatal care consultations. Plasmodium falciparum infection was diagnosed using rapid diagnostic test (RDT), microscopy and polymerase chain reaction (PCR). Haemoglobin concentration was also determined.

Results

In total, 332 pregnant women were enrolled. RDT and microscopy data were available for all the blood samples and 166 samples were analysed by PCR. The prevalence of asymptomatic P. falciparum infection using microscopy, RDTs and PCR, were respectively 21.6%, 27.4% and 29.5%. Taking PCR as a reference, RDTs had a sensitivity of 81.6% and a specificity of 94.9% to diagnose asymptomatic P. falciparum infection. The corresponding values for microscopy were 67.3% and 97.4%. The prevalence of anaemia was 61.1% and asymptomatic malaria increased five times the odds (p < 0.001) of having anaemia. RDTs were more cost-effective compared to microscopy. Incremental cost-effectiveness ratio was US$ 63.47 per microscopy adequately diagnosed case.

Conclusion

These alarming results emphasize the need to actively diagnose and treat asymptomatic malaria infection during all antenatal care visits. Moreover, in DRC, malaria and anaemia control efforts should be strengthened by promoting the use of insecticide-treated nets, intermittent preventive treatment with sulphadoxine-pyrimethamine and iron and folic acid supplements.

Plasmodium falciparum mutant haplotype infection during pregnancy associated with reduced birthweight, Tanzania

Intermittent preventive treatment during pregnancy with sulfadoxine–pyrimethamine (IPTp-SP) is a key strategy in the control of pregnancy-associated malaria. However, this strategy is compromised by widespread drug resistance from single-nucleotide polymorphisms in the Plasmodium falciparum dihydrofolate reductase and dihydropteroate synthetase genes. During September 2008–October 2010, we monitored a cohort of 924 pregnant women in an area of Tanzania with declining malaria transmission. P. falciparum parasites were genotyped, and the effect of infecting haplotypes on birthweight was assessed. Of the genotyped parasites, 9.3%, 46.3%, and 44.4% had quadruple or less, quintuple, and sextuple mutated haplotypes, respectively. Mutant haplotypes were unrelated to SP doses. Compared with infections with the less-mutated haplotypes, infections with the sextuple haplotype mutation were associated with lower (359 g) birthweights. Continued use of the suboptimal IPTp-SP regimen should be reevaluated, and alternative strategies (e.g., intermittent screening and treatment or intermittent treatment with safe and effective alternative drugs) should be evaluated.

Evaluation of Paracheck-Pf(TM) rapid malaria diagnostic test for the diagnosis of malaria among HIV-positive patients in Ibadan, south-western Nigeria

Febrile illnesses occur frequently among HIV positive patients and these are often treated presumptively as malaria in endemic areas. Parasite-based diagnosis of malaria will eliminate unnecessary treatment, reduce drug-drug interactions and the chances for the emergence of drug resistant Plasmodium. We evaluated finger prick blood samples from 387 people living with HIV (PLWHIV) and suspected of having malaria by expert microscopy and Paracheck-Pf(TM) - a histidine-rich protein-II based malaria rapid diagnostic test. The study was conducted at the PEPFAR supported AIDS Prevention Initiative in Nigeria (APIN) Clinic of the University College Hospital Ibadan, southwest Nigeria. Outcome parameters were prevalence of malaria parasitemia, sensitivity and specificity of Paracheck-Pf as well as the positive and negative predictive values for Paracheck-Pf using microscopy of Giemsa-stained blood film as gold standard. Malaria parasites were detected in 19·1% (74/387) of enrollees by microscopy and 19·3% (74/383) by Paracheck-Pf. Geometric mean parasite density was 501/μl (range 39-749 202/μl). Sensitivity and specificity of Paracheck-Pf at all parasite densities were 55·4% and 89·3% while corresponding figures at parasite densities ≥200/μl were 90·9% and 90·3%. Sensitivity and specificity at parasite densities ≥500/μl was 97·6% and 90·3%. Positive and negative predictive values for parasite density ≥200/μl were 55·4% and 98·7%, respectively. Paracheck-Pf was found to be a useful malaria diagnostic tool at parasite densities ≥200/μl facilitating appropriate clinical management.

Gestational age-related changes in the peripheral blood cell composition of sub-Saharan African women

Gestational age-related changes in the cellular composition of peripheral blood have not been described in sub-Saharan African settings. We conducted longitudinal cohort studies in Beninese and Tanzanian mothers with quantification of peripheral blood mononuclear cell-types ex vivo using flow cytometry. Between the second trimester and delivery the frequency of CD4(+) T cells declined significantly, contrasting with a non-significant increase in CD8(+) T cells, but no changes in T-regulatory, NK or NKT cell frequencies. Antigen-presenting cell profiles were also unaltered, although non-significant trends were evident. These changes resemble in some respects those reported during pregnancies in developed countries, but differ in others.

Reliability of rapid diagnostic test for diagnosing peripheral and placental malaria in an area of unstable malaria transmission in Eastern Sudan

BACKGROUND

Diagnosing Plasmodium falciparum malaria during pregnancy is a great challenge for clinicians because of the low density of parasites in the peripheral blood and parasite sequestration in the placenta. Nevertheless, few data on the use of malaria rapid diagnostic test (RDT) during pregnancy have been published.

METHODS

P. falciparum infections were assessed in 156 febrile pregnant women by microscopic examination of their blood smears and by RDT and polymerase chain reactions (PCR). In addition, 150 women were assessed at the time of delivery by microscopy, RDT, PCR and placental histology investigations. The study was conducted at the Gadarif Hospital, Eastern Sudan. The SD Bioline P. f / P. v (Bio Standard Diagnostics, Gurgaon, Korea) RDT kit was evaluated in this study.

RESULTS

Among the febrile pregnant women, 17 (11.0%), 26 (16.7%) and 18 (11.5%) positive cases of P. falciparum were detected by microscopy, RDT, and PCR, respectively. The sensitivity and specificity of the microscopy was 94.4% and 100%, respectively. The corresponding values for RDT evaluation were 83.3% and 92.0%, as compared with PCR as the gold standard.While there were no detected cases of malaria by microscopic examination of blood smears, 27 (18.0%), 21(14.0%) and 46 (30.7%) out of the 150 placentae investigated had P. falciparum as determined by RDT, PCR, and histology, respectively. The sensitivity and specificity for RDT was 17.4% and 81.7%, respectively. The corresponding values for PCR were 6.5% and 82.7%, where histology was used as the gold standard.

CONCLUSIONS

The RDT kit used in this study has poor performance for peripheral and placental P. falciparum malaria detection in this setting.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1092363465928479.

Malaria and fetal growth alterations in the 3(rd) trimester of pregnancy: a longitudinal ultrasound study

Background

Pregnancy associated malaria is associated with decreased birth weight, but in-utero evaluation of fetal growth alterations is rarely performed. The objective of this study was to investigate malaria induced changes in fetal growth during the 3^rd trimester using trans-abdominal ultrasound.

Methods

An observational study of 876 pregnant women (398 primi- and secundigravidae and 478 multigravidae) was conducted in Tanzania. Fetal growth was monitored with ultrasound and screening for malaria was performed regularly. Birth weight and fetal weight were converted to z-scores, and fetal growth evaluated as fetal weight gain from the 26th week of pregnancy.

Results

Malaria infection only affected birth weight and fetal growth among primi- and secundigravid women. Forty-eight of the 398 primi- and secundigravid women had malaria during pregnancy causing a reduction in the newborns z-score of −0.50 (95% CI: −0.86, −0.13, P = 0.008, multiple linear regression). Fifty-eight percent (28/48) of the primi- and secundigravidae had malaria in the first half of pregnancy, but an effect on fetal growth was observed in the 3^rd trimester with an OR of 4.89 for the fetal growth rate belonging to the lowest 25% in the population (95%CI: 2.03–11.79, P<0.001, multiple logistic regression). At an individual level, among the primi- and secundigravidae, 27% experienced alterations of fetal growth immediately after exposure but only for a short interval, 27% only late in pregnancy, 16.2% persistently from exposure until the end of pregnancy, and 29.7% had no alterations of fetal growth.

Conclusions

The effect of malaria infections was observed during the 3^rd trimester, despite infections occurring much earlier in pregnancy, and different mechanisms might operate leading to different patterns of growth alterations. This study highlights the need for protection against malaria throughout pregnancy and the recognition that observed changes in fetal growth might be a consequence of an infection much earlier in pregnancy.