Study of the diagnostic accuracy of microbiological techniques in the diagnosis of malaria in the immigrant population in Madrid

Nine years of imported malaria in a teaching hospital in Belgium: Demographics, clinical characteristics, and outcomes

BACKGROUND

Imported malaria is often misdiagnosed due to the aspecific symptoms and lack of familiarity among clinicians. This study aims to evaluate a decade-long trend of imported malaria cases in a Belgian teaching hospital by analyzing demographics, clinical characteristics, and outcomes.

METHODS

Medical records of 223 patients with confirmed malaria diagnoses between 2010 and 2019 were analyzed.

RESULTS

Most patients were male (63.2%), aged 18-65 years (77.1%), and visiting friends or relatives (40.8%). Central Africa was the most common travel destination (54.3%), and 63.7% did not take prophylaxis. Symptoms were flu-like, with fever (91.9%) being most prevalent. P. falciparum was identified in 88.3% of cases. A high proportion of severe cases (41.7%) and a low mortality rate (0.9%) were recorded. A severe form of the disease is associated with a more extended hospital stay than uncomplicated form (median of 5 vs. 4 days, p < 0.001). Thirty-five-point five percent [33/93] of patients with severe malaria have had a previous malaria infection compared to 50.8% [66/130] of uncomplicated patients (p= 0.013) wich was statistically significant.

CONCLUSION

Malaria disproportionately affects VFRs traveling to Central Africa, and flu-like symptoms should raise suspicion. Prophylaxis is essential to prevent the disease, and early diagnosis is critical for effective management. A severe form of the disease is associated with a more extended hospital stay than uncomplicated form and people with a previous history of malaria have a less severe disease.

Malaria parasite prevalence among migrants: a systematic review and meta-analysis

BACKGROUND

Asymptomatic malaria infections are highly prevalent in endemic areas.

OBJECTIVES

This systematic review aimed to estimate the pooled prevalence of malaria parasites in migrants screened in non-endemic areas.

DATA SOURCES

MEDLINE-Ovid, EMBASE, Web of Science, Global Health, Lilacs, Cochrane, and MedRxiv.

STUDY ELIGIBILITY CRITERIA

Cross-sectional studies and observational prospective or retrospective cohort studies conducted in Europe, USA, Canada, Australia, or New Zealand regardless of language or publication status. Studies should include prevalence data on malaria in migrants that were recruited through a systematic screening approach. We excluded studies where people were tested because of malaria symptoms.

PARTICIPANTS

Migrant individuals exposed to malaria infection ASSESSMENT OF RISK OF BIAS: A standardized and validated appraisal instrument was used for studies reporting prevalence data (Joanna Briggs Institute Manual for Evidence Synthesis).

METHODS OF DATA SYNTHESIS

Pooled estimates of the parasite prevalence by PCR, microscopy, and rapid diagnostic test (RDT) were calculated with a random-effects model. Heterogeneity was explored by stratification by age, region of origin, period of study, and quality of studies.

RESULTS

Of 1819 studies retrieved, 23 studies were included with in total 4203 participant PCR data, 3186 microscopy and 4698 RDT data, respectively. Migrants from sub-Saharan Africa had a malaria parasite prevalence of 8.3% (95% CI 5.1-12.2) by PCR, 4.3% (1.5-8.2) by RDT, and 3.1% (0.7-6.8) by microscopy. For migrants from Asia and Latin America, the prevalence with PCR was 0% (0.0-0.08) and 0.4% (0.0-1.8), respectively. Migrants from the Central African Region had the highest PCR prevalence (9.3% [6.0-13.0]), followed by West African migrants (2.0% [0.0-7.7]). Restricting the analysis to sub-Saharan Africa migrants arriving to the host country within the previous year, the PCR-based prevalence was 11.6% (6.9-17.4).

CONCLUSION

We provide estimates on the malaria parasite prevalence in migrants in non-endemic setting. Despite heterogeneity between settings, these findings can contribute to inform screening strategies and guidelines targeting malaria in migrants.

Malaria Diagnosis in Non-Endemic Settings: The European Experience in the Last 22 Years

Accurate, prompt, and reliable tools for the diagnosis of malaria are crucial for tracking the successes or drawbacks of control and elimination efforts, and for future programs aimed at global malaria eradication. Although microscopy remains the gold standard method, the number of imported malaria cases and the risk of reappearance of autochthonous cases stimulated several laboratories located in European countries to evaluate methods and algorithms suited to non-endemic settings, where skilled microscopists are not always available. In this review, an overview of the field evaluation and a comparison of the methods used for the diagnosis of malaria by European laboratories is reported, showing that the development of numerous innovations is continuous. In particular, the combination of rapid diagnostic tests and molecular assays with microscopy represents a reliable system for the early diagnosis of malaria in non-endemic settings.

Bayesian evaluation of the performance of three diagnostic tests for Plasmodium falciparum infection in a low-transmission setting in Kilifi County, Kenya

Background: Central to the successful elimination of Plasmodium falciparum malaria, are tests with superior capability of diagnosing low-density parasitaemias. Empirical evidence on the performance of the commonly available diagnostics (light microscopy (LM), rapid diagnostic tests (RDT) and polymerase chain reaction (PCR)) is needed to better inform case management and surveillance activities within primary health care settings where elimination of falciparum malaria is targeted. The objective of this study was to estimate the sensitivity (Se) and specificity (Sp) and predictive values of LM, RDT and PCR tests for P. falciparum infection in children, while evaluating the effect of specific covariates on the accuracy of the tests. Methods: The study enrolled 1,563 children presenting with fever (axillary temperature ≥ 37.5 0C) to the Ngerenya dispensary, Kilifi County between March and December 2014. A Bayesian latent class model (BLCM) was fitted to the participants' diagnostic data obtained from blood samples that were screened for the presence of P. falciparum using the three tests. Results: The PCR assay registered a higher Se (97.6% [92.0; 99.7]) than LM (84.0% [74.8; 91.0]) but similar to RDT (92.2% [84.4; 97.0]). However, the assay showed a similar Sp (98.9% [98.2; 99.4]) to both RDT (99.4% [98.9; 99.7]) and LM (99.5% [99.0; 99.8]). Regarding predictive values, the tests yielded statistically similar estimates of positive and negative predictive values (PPV and NPV). A serial interpretation of the results of RDT and LM raised the PPVs and NPVs to >98%. Conclusions: LM and RDT afford high Se and Sp in symptomatic care-seeking children in this low P. falciparum prevalence setting. A serial combination of the tests assures high PPV and NPV estimates. These elements, coupled with the wide deployment and affordability of the tests, lend the tests useful for guiding clinical care and surveillance activities for P. falciparum within elimination settings.

Diagnosis of malaria in a traveler 9 months after returning from West Africa by illumigene® LAMP assay: A case report

Loop-mediated isothermal amplification (LAMP) is a rapid molecular technique that has been introduced into malaria diagnosis. The test is easy to perform and offers high sensitivity. We report a 53-year-old male patient who was hospitalized with fever attacks, chills, and headache caused 9 months after returning from Africa. During his stay in Africa, he used malaria chemoprophylaxis. Microscopy of thin and thick blood films and rapid diagnostic antigen testing remained negative for three times. The EDTA blood samples were tested using the Meridian illumigene® malaria LAMP assay that gave a positive result for Plasmodium spp. Diagnosis of malaria was subsequently specified as P. ovale infection by real-time PCR. Ovale malaria often manifests with delay and low parasitemia. The patient was treated with atovaquone-proguanil, followed by primaquine for prophylaxis of relapse. This case illustrates the usefulness of the illumigene® malaria LAMP assay for initial screening of malaria parasites.

Bayesian evaluation of the performance of three diagnostic tests for Plasmodium falciparum infection in a low-transmission setting in Kilifi County, Kenya

Background: Central to the successful elimination of Plasmodium falciparum malaria, are tests with superior capability of diagnosing low-density parasitaemias. Empirical evidence on the performance of the commonly available diagnostics (light microscopy (LM), rapid diagnostic tests (RDT) and polymerase chain reaction (PCR)) is needed to better inform case management and surveillance activities within primary health care settings where elimination of falciparum malaria is targeted. The objective of this study was to estimate the sensitivity (Se) and specificity (Sp) and predictive values of LM, RDT and PCR tests for P. falciparum infection in children, while evaluating the effect of specific covariates on the accuracy of the tests. Methods: The study enrolled 1,563 children presenting with fever (axillary temperature ≥ 37.50C) to the Ngerenya dispensary, Kilifi County between March and December 2014. A Bayesian latent class model (BLCM) was fitted to the participants' diagnostic data obtained from blood samples that were screened for the presence of P. falciparum using the three tests. Results: The PCR assay registered a higher Se (97.6% [92.0; 99.7]) than LM (84.0% [74.8; 91.0]) but similar to RDT (92.2% [84.4; 97.0]). However, the assay showed a similar Sp (98.9% [98.2; 99.4]) to both RDT (99.4% [98.9; 99.7]) and LM (99.5% [99.0; 99.8]). Regarding predictive values, the tests yielded statistically similar estimates of positive and negative predictive values (PPV and NPV). A serial interpretation of the results of RDT and LM raised the PPVs and NPVs to >98%. Conclusions: LM and RDT afford high Se and Sp in a low P. falciparum prevalence setting. A serial combination of the tests assures high PPV and NPV estimates. These elements, coupled with the wide deployment and affordability of the tests, lend the tests useful for guiding clinical care and surveillance activities for P. falciparum within elimination settings.

Prevalence of submicroscopic malaria infection in immigrants living in Spain

BACKGROUND

The importance of submicroscopic malaria infections in high-transmission areas could contribute to maintain the parasite cycle. Regarding non-endemic areas, its importance remains barely understood because parasitaemia in these afebrile patients is usually below the detection limits for microscopy, hence molecular techniques are often needed for its diagnosis. In addition to this, the lack of standardized protocols for the screening of submicroscopic malaria in immigrants from endemic areas may underestimate the infection with Plasmodium spp. The aim of this study was to assess the prevalence of submicroscopic malaria in afebrile immigrants living in a non-endemic area.

METHODS

A prospective, observational, multicentre study was conducted. Afebrile immigrants were included, microscopic observation of Giemsa-stained thin and thick blood smears, and two different molecular techniques detecting Plasmodium spp. were performed. Patients with submicroscopic malaria were defined as patients with negative blood smears and detection of DNA of Plasmodium spp. with one or both molecular techniques. Demographic, clinical, analytical and microbiological features were recorded and univariate analysis by subgroups was carried out with STATA v15.

RESULTS

A total of 244 afebrile immigrants were included in the study. Of them, 14 had a submicroscopic malaria infection, yielding a prevalence of 5.7% (95% confidence interval 3.45-9.40). In 71.4% of the positive PCR/negative microscopy cases, Plasmodium falciparum alone was the main detected species (10 out of the 14 patients) and in 4 cases (28.6%) Plasmodium vivax or Plasmodium ovale were detected. One patient had a mixed infection including three different species.

CONCLUSIONS

The prevalence of submicroscopic malaria in afebrile immigrants was similar to that previously described in Spain. Plasmodium vivax and P. ovale were detected in almost a third of the submicroscopic infections. Screening protocols for afebrile immigrants with molecular techniques could be useful for a proper management of these patients.