Dados do Trabalho

Título

Hemozoin-based device for vivax malaria diagnosis

Objetivo (s)

The aim of this study was to evaluate the diagnostic performance of Gazelle™ compared to optical microscopy, RDT and PCR in detecting vivax malaria in the western Brazilian amazon.

Material e Métodos

Ethics statement
The study was approved by the Ethics Review Board of Fundação de Medicina Tropical Dr Heitor Vieira Dourado (FMT-HVD) (3.374.472/2019).

Selection of patients
A cross-sectional study was carried out between June and October 2019 at FMT-HVD.
The study included patients of either sex who were infected with P. vivax or non-infected, ≥18 years of age. Exclusion criteria were severe malaria, pregnant woman and use of antimalarials in the previous 30 days.

Malaria diagnosis
Evaluated by Microscopy (thick blood smears, stained by Giemsa), RDT (Malaria Ag Pf/Pan RDT – SD Bioline), PCR (QMAL Taqman qPCR in the 7500 Fast Real-Time PCR System), and Gazelle™ device (Hemex Health Inc.).

Statistical analysis
Gazelle™ malaria diagnostic performance measures that were assessed included: sensitivity, specificity, likelihood ratios (LR), positive predictive value (PPV), negative predictive value (NPV) and quantitation accuracy. Diagnosis was compared using optical microscopy, RDT or PCR as reference. Analysis was performed on STATA (v13.1, StataCorp, College Station, TX, USA).

Resultados e Conclusão

RESULTS
A total of 300 patients were recruited into the study. 24 samples were later excluded from analysis. Out of the 276 patients analyzed in this study, 161 (58.3%) were male with a mean age of 40 (18-79) years.
Malaria-positive samples were 109/276 (39.5%) by RDT, 130/276 (47.1%) by microscopy, 172/276 (62.3%) by PCR, and 125/276 (45.3%) by Gazelle™.
Sensitivity compared with microscopy was 96.1%, compared with RDT was 100%, and 72.1% compared to qPCR. Specificity compared with microscopy was 100%, in comparison to RDT was 90.4% and compared to PCR was 99.0%.
PPV of 100% compared to microscopy; of 87.2% compared to RDT and of 99.2% compared to PCR. NPV of 96.7% compared to microscopy; of 100% compared to RDT and of 68.21% compared to PCR.
Given Gazelle™ against parasite density of parasites/µl (microscopy) the cutoff was 100 parasites/µl. Against PCR copies/µl (PCR), the curves crossed at 1000 PCR copies/µl.

CONCLUSION
Gazelle™ has shown good sensitivity, specificity and accuracy when compared to the microscopy and other methods for vivax malaria diagnosis.

Palavras-chave

Malaria, Plasmodium vivax, diagnostic test, hemozoin, magnetic-optical detection.

Agradecimentos

Hemex Health Inc., manufacturer of Gazelle device, financed the study.