Towards malaria microscopy at the point-of-contact: an assessment of the diagnostic performance of the Newton Nm1 microscope in Uganda

Parasitology ◽  
2014 ◽  
Vol 141 (14) ◽  
pp. 1819-1825 ◽  
Author(s):  
J. RUSSELL STOTHARD ◽  
BETTY NABATTE ◽  
JOSE C. SOUSA-FIGUEIREDO ◽  
NARCIS B. KABATEREINE
Keyword(s):  
Confidence Interval ◽  
Positive Predictive Value ◽  
Predictive Value ◽  
Blood Cells ◽  
Diagnostic Performance ◽  
White Blood Cells ◽  
Sub Saharan Africa ◽  
Resource Poor ◽  
Sub Saharan ◽  
Malaria Microscopy

SUMMARYMalaria microscopy in sub-Saharan Africa is often restricted by access to light microscopes. To address this gap, a novel portable inverted monocular microscope, the Newton Nm1, was designed and is now commercially available. Its diagnostic performance was assessed in a blinded-slide trial at ×1000 (oil) of Giemsa-stained thick blood films against a conventional microscope as undertaken by four Ugandan Ministry of Health technicians. With the Newton Nm1, diagnostic performance was: sensitivity 93·5% (95% confidence interval (CI) 78·6–99·2%), specificity 100·0% (95% CI 82·4–100·0%), positive predictive value 100·0% (95% CI 88·1–100·0%) and negative predictive value 90·5% (95% CI 69·6–98·8%). Discordance was due to a systematic error underestimating parasitaemia by ~45%; when counting Plasmodium parasites against 200 white blood cells, blood films with low parasitaemia (i.e. <100 μL−1 of blood) could be overlooked and misclassified. By contrast, specificity was excellent with no false positives encountered. Whilst proven useful, especially in resource-poor environments, it is still unclear how we can ensure the uptake of the Newton Nm1 within sub-Saharan Africa.

A multi-state spatio-temporal Markov model for categorized incidence of meningitis in sub-Saharan Africa

2012 ◽  
Vol 141 (8) ◽  
pp. 1764-1771 ◽  
Author(s):  
L. AGIER ◽  
M. STANTON ◽  
G. SOGA ◽  
P. J. DIGGLE
Keyword(s):  
Positive Predictive Value ◽  
Predictive Value ◽  
Public Health Problem ◽  
Incidence Rates ◽  
Sub Saharan Africa ◽  
Major Public Health Problem ◽  
Temporal Dependence ◽  
Spatio Temporal ◽  
Sub Saharan ◽  
Annual Scale

SUMMARYMeningococcal meningitis is a major public health problem in the African Belt. Despite the obvious seasonality of epidemics, the factors driving them are still poorly understood. Here, we provide a first attempt to predict epidemics at the spatio-temporal scale required for in-year response, using a purely empirical approach. District-level weekly incidence rates for Niger (1986–2007) were discretized into latent, alert and epidemic states according to pre-specified epidemiological thresholds. We modelled the probabilities of transition between states, accounting for seasonality and spatio-temporal dependence. One-week-ahead predictions for entering the epidemic state were generated with specificity and negative predictive value >99%, sensitivity and positive predictive value >72%. On the annual scale, we predict the first entry of a district into the epidemic state with sensitivity 65·0%, positive predictive value 49·0%, and an average time gained of 4·6 weeks. These results could inform decisions on preparatory actions.

scholarly journals Evaluation of the Dynamiker Cryptococcal Antigen Lateral Flow Assay for the Diagnosis of HIV-Associated Cryptococcosis

2020 ◽  
Author(s):  
Richard Kwizera ◽  
Denis Omali ◽  
Kiiza Tadeo ◽  
John Kasibante ◽  
Morris K. Rutakingirwa ◽  
...  
Keyword(s):  
Predictive Value ◽  
Diagnostic Performance ◽  
Point Of Care ◽  
Lateral Flow ◽  
Lateral Flow Assay ◽  
Sub Saharan Africa ◽  
Serum Samples ◽  
Cryptococcal Antigen ◽  
Asymptomatic Patients ◽  
Sub Saharan

Background: Cryptococcal meningitis is a leading cause of meningitis in sub-Saharan Africa. Given the need for rapid point of care testing, we evaluated the diagnostic performance of the Dynamiker cryptococcal antigen (CrAg) lateral flow assay (LFA). Methods: We assessed the diagnostic performance of the Dynamiker CrAg-LFA compared to the IMMY CrAg-LFA as the reference standard. We tested 150 serum, 115 plasma, 100 cerebrospinal fluid (CSF) samples from HIV patients with symptomatic meningitis and 113 serum samples from patients with suspected asymptomatic cryptococcal antigenemia. Results: Compared to the IMMY CrAg-LFA, sensitivity of Dynamiker CrAg-LFA was 98% in serum, 100% in plasma, 100% in CSF from symptomatic patients and 96% in serum from asymptomatic patients. Specificity was 66% in serum, 61% in plasma, 91% in CSF from symptomatic patients, and 86% in serum from asymptomatic patients. The positive predictive value was 85% in serum, 82% in plasma, 96% in CSF from symptomatic patients, and 69% in serum from asymptomatic patients. The negative predictive value was 94% in serum, 100% in plasma, 100% in CSF from symptomatic patients, and 99% in serum from asymptomatic patients. The inter-assay reproducibility was 100% across the four sample types with no observed discordant results when Dynamiker CrAg-LFA was tested in duplicate. However, a high number of false positives were observed on serum of symptomatic patients (11%), serum of asymptomatic patients (11%) and plasma of symptomatic patients (14%). Conclusion: The Dynamiker CrAg-LFA had excellent sensitivity but poor specificity, particularly when tested on serum and plasma.

scholarly journals Impact of rural versus urban setting on kidney markers: a cross-sectional study in South-Kivu, DRCongo

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Mannix Imani Masimango ◽  
Michel P. Hermans ◽  
Espoir Bwenge Malembaka ◽  
Pierre Wallemacq ◽  
Ernest Kiswaya Sumaili ◽  
...  
Keyword(s):  
Positive Predictive Value ◽  
Negative Predictive Value ◽  
Predictive Value ◽  
Democratic Republic Of Congo ◽  
Urban Setting ◽  
Sub Saharan Africa ◽  
Rural Site ◽  
Urban Site ◽  
Cross Sectional ◽  
South Kivu

Abstract Background Most studies of chronic kidney disease (CKD) in Sub-Saharan Africa (SSA) have been conducted in urban settings. They relied on GFR estimated from serum creatinine alone and on the inexpensive, convenient urinary dipstick to assess proteinuria. The dipstick for proteinuria has not been directly compared with the gold standard albumin-to-creatinine ratio (ACR) in a large-sized study in SSA. We hereby assessed the influence of rural versus urban location on the level, interpretation, and diagnostic performance of proteinuria dipstick versus ACR. Methods In a cross-sectional population-based study of CKD in both urban (n = 587) and rural (n = 730) settings in South-Kivu, Democratic Republic of Congo (DRC), we assessed the prevalence, performance (sensitivity, specificity, positive predictive value and negative predictive value) and determinants of a positive dipstick proteinuria as compared with albuminuria (ACR). Albuminuria was subdivided into: A1 (< 30 mg/g creatinine), A2 (30 to 299 mg/g creatinine) and A3 (≥ 300 mg/g creatinine). Results The overall prevalence of positive dipstick proteinuria (≥ 1+) was 9.6 % (95 % CI, 7.9–11.3) and was higher in rural than in urban residents (13.1 % vs. 4.8 %, p < 0.001), whereas the prevalence of albuminuria (A2 or A3) was similar in both sites (6 % rural vs. 7.6 % urban, p = 0.31). In both sites, dipstick proteinuria ≥ 1 + had a poor sensitivity (< 50 %) and positive predictive value (< 11 %) for the detection of A2 or A3. The negative predictive value was 95 %. Diabetes [aOR 6.12 (1.52–24.53)] was a significant predictor of A3 whereas alkaline [aOR 7.45 (3.28–16.93)] and diluted urine [aOR 2.19 (1.35–3.57)] were the main predictors of positive dipstick proteinuria. Conclusions ACR and dipstick proteinuria have similar positivity rates in the urban site whereas, in the rural site, dipstick was 2-fold more often positive than ACR. The poor sensitivity and positive predictive value of the dipstick as compared with ACR makes it unattractive as a screening tool in community studies of CKD in SSA.

scholarly journals The Scope and Appetite for Technology-Assisted Sensitivity Reviewing of Born-Digital Records in a Resource Poor Environment

2018 ◽  
pp. 175-182 ◽  
Author(s):  
Alistair G. Tough
Keyword(s):  
Effective Means ◽  
Sub Saharan Africa ◽  
Public Records ◽  
Digital Repositories ◽  
Resource Poor ◽  
Preliminary Research ◽  
Sub Saharan ◽  
The University ◽  
Limited Demand ◽  
Assessing Sensitivity

Concerns about sensitive content in born-digital records seem to be a major factor in inhibiting the deposit of public records in dedicated digital repositories in Western countries. These concerns are much exacerbated by the changed nature of the process of reviewing records. The University of Glasgow, working in collaboration with the Foreign and Commonwealth Office, received funding to investigate the technology-assisted sensitivity reviewing of born-digital records. As part of this research, some preliminary research in a commonwealth country in Sub-Saharan Africa was carried out. The research, reported in this chapter, was carried out in Malawi by the late Dr. Mathews J. Phiri. He found that already there is a real, albeit limited, demand for technology-assisted sensitivity reviewing of born-digital records in Malawi. The available evidence suggests that within the next decade there is likely to be an increase in the need for effective means of assessing sensitivity in born-digital records.

E-Service Innovation in Rural Africa Through Value Co-Creation

2017 ◽  
pp. 355-373
Author(s):  
Anna Bon ◽  
Jaap Gordijn ◽  
Hans Akkermans
Keyword(s):  
Business Model ◽  
Service Innovation ◽  
End Users ◽  
Sub Saharan Africa ◽  
Resource Poor ◽  
Local Stakeholders ◽  
Rural Africa ◽  
Sub Saharan ◽  
Electricity Infrastructure

E-Services have great potential, even in resource-poor environments such as in sub-Saharan Africa. However, contextual factors pose significant challenges for development, feasibility, deployment and sustainability of e-services. This chapter presents a case of e-service value co-creation in a rural context, with targeted end users in regions characterized by limited electricity infrastructure and poor or absent internet, strong diversity in languages spoken, high illiteracy rates and limited purchasing power. It offers a methodology to upfront analyze business model sustainability for e-service innovation in severely resource-constrained contexts. This is illustrated by an extensive case study in which a voice-based microblogging e-service was developed and deployed with local stakeholders in rural Mali.

Malaria

2019 ◽  
Author(s):  
Angelina Jayakumar ◽  
Zahir Osman Eltahir Babiker
Keyword(s):  
Southeast Asia ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Parasitic Infection ◽  
Sub Saharan Africa ◽  
Anopheline Mosquito ◽  
Sub Saharan ◽  
The Uk ◽  
Almost All ◽  
Human Infections

Malaria is a tropical parasitic infection of the red blood cells caused by the protozoal species Plasmodium falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi. It is transmitted through the bite of the female Anopheles mosquito. The average incubation period is twelve to fourteen days. Congenital and blood-borne transmissions can also occur. P. falciparum and P. vivax account for most human infections but almost all deaths are caused by P. falciparum, with children under five years of age bearing the brunt of morbidity and mortality in endemic countries. P. falciparum is dominant in sub-Saharan Africa whereas P. vivax predominates in Southeast Asia and the Western Pacific. P. ovalae and P. malaria are less common and are mainly found in sub-Saharan Africa. P. knowlesi primarily causes malaria in macaques and is geographically restricted to southeast Asia. While taking a blood meal, the female anopheline mosquito injects motile sporozoites into the bloodstream. Within half an hour, the sporozoites invade the hepatocytes and start dividing to form tissue schizonts. In P. vivax and P. ovale, some of the sporozoites that reach the liver develop into hypnozoites and stay dormant within the hepatocytes for months to years after the original infection. The schizonts eventually rupture releasing daughter merozoites into the bloodstream. The merozoites develop within the red blood cells into ring forms, trophozoites, and eventually mature schizont. This part of the life cycle takes twenty-four hours for P. knowlesi; forty-eight hours for P. falciparum, P. vivax, P. ovale; and seventy-two hours for P. malariae. In P. vivax and P. ovale, some of the sporozoites that reach the liver develop into hypnozoites and stay dormant within the hepatocytes for months to years after the original infection. The hallmark of malaria pathogenesis is parasite sequestration in major organs leading to cytoadherence, endothelial injury, coagulopathy, vascular leakage, pro-inflammatory cytokine production, and tissue inflammation. Malaria is the most frequently imported tropical disease in the UK with an annual case load of around 2000. P. falciparum is the predominant imported species, and failure to take chemoprophylaxis is the commonest risk factor.

scholarly journals Validity of four clinical prediction scores for pulmonary embolism in a sub-Saharan African setting: a protocol for a Cameroonian multicentre cross-sectional study

BMJ Open ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. e031322
Author(s):  
Agnès Esiéné ◽  
Paul Owono Etoundi ◽  
Joel Noutakdie Tochie ◽  
Junette Arlette Mbengono Metogo ◽  
Jacqueline Ze Minkande
Keyword(s):  
Pulmonary Embolism ◽  
Emergency Departments ◽  
Diagnostic Performance ◽  
Cross Sectional Study ◽  
Sub Saharan Africa ◽  
Receiver Operating Curve ◽  
Clinical Prediction ◽  
Sectional Study ◽  
Cross Sectional ◽  
Sub Saharan

IntroductionPulmonary embolism poses one of the most challenging diagnoses in medicine. Resolving these diagnostic difficulties is more crucial in emergency departments where fast and accurate decisions are needed for a life-saving purpose. Here, clinical pretest evaluation is an important step in the diagnostic algorithm of pulmonary embolism. Although clinical probability scores are widely used in emergency departments of sub-Saharan Africa, no study has cited their diagnostic performance in this resource-constrained environment. This study will seek to assess the performance of four routinely used clinical prediction models in Cameroonians presenting with suspicion of pulmonary embolism at the emergency department.Methods and analysisIt will be a cross-sectional study comparing the sensitivity, specificity, positive and negative predictive values and accuracy of the Wells, Simplified Wells, Revised Geneva and the Simplified Revised Geneva Scores to CT pulmonary angiography as gold standard in all consecutive consenting patients aged above 15 years admitted for clinical suspicion of pulmonary embolism to the emergency departments of seven major referral hospitals of Cameroon between 1 July 2019 and 31 December 2020. The area under the receiver operating curve, calibration plots, Hosmer and Lemeshow statistics, observed/expected event rates, net benefit and decision curve will be measured of each the clinical prediction test to ascertain the clinical score with the best diagnostic performance.Ethics and disseminationClearance has been obtained from the Institutional Review Board of the Faculty of medicine and biomedical sciences of the University of Yaounde I, Cameroon and the directorates of all participating hospitals to conduct this study. Also, informed consent will be sought from each patient or their legal next of kin and parents for minors, before enrolment into this study. The final study will be published in a peer-review journal and the findings presented to health authorities and healthcare providers.

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