Evaluación de campo de la precisión de la prueba de diagnóstico rápido SD Bioline Malaria Antigen Pf/Pv® en Colombia / Field evaluation for diagnostic accuracy of the rapid test SD Bioline Malaria Antigen Pf/Pv® in Colombia

Introducción. Las pruebas de diagnóstico rápido han sido postuladas como una forma de garantizar el diagnóstico de malaria, o paludismo, en zonas de difícil acceso. A pesar de su uso difundido, no hay estudios de campo que evalúen la precisión de la prueba de diagnóstico rápido SD Bioline Malaria Antigen Pf/Pv® en Colombia. Objetivo. Evaluar la precisión diagnóstica de la prueba de diagnóstico rápido SD Bioline Malaria Antigen Pf/Pv ®, en dos departamentos endémicos para malaria, comparando el diagnóstico con la gota gruesa corregida por reacción en cadena de la polimerasa (PCR). Materiales y métodos. Se trata de un estudio retrospectivo para evaluar sensibilidad, especificidad, valor diagnóstico positivo (VPP) y negativo (VPN), concordancia y límites de sensibilidad por rangos de parasitemia, de la prueba SD Bioline Malaria Antigen ® Pf/Pv, en Córdoba y Chocó. Los resultados fueron comparados con la gota gruesa corregida por PCR. Resultados. De 383 muestras procesadas, 121 fueron positivas (75 para Plasmodium vivax, 42 para P. falciparum y 4 para infección mixta) y 262 muestras negativas; los resultados obtenidos fueron los siguientes: P. vivax: sensibilidad, 92,0 % (IC 95% 83,6-96,3); especificidad, 98,7 % (IC 95% 96,7-99,5); VPP, 94,5 % (IC 95% 86,7-97,9); VPN, 98,1 % (IC 95% 95,8-99,1); IK, 0,90 (0,80-1,00). P. falciparum: sensibilidad, 88,1 % (IC 95% 75,0-94,8); especificidad, 97,9 % (IC 95% 95,8-99,0); VPP, 84,1% % (IC 95% 70,6-92,1); VPN, 98,5 % (IC 95% 96,6-99,4); IK, 0,80 (0,70-0,90). Conclusiones. La prueba tuvo un buen desempeño, siendo mejor para P. vivax en comparación con que para P. falciparum. Persisten dificultades en la detección de bajas parasitemias. La falta de amplificación de los genes Pfhrp2 y Pfhrp3 en dos muestras con diagnóstico de como infección mixta, sugiere una posible deleción conjunta de estos genes.

Introduction: Rapid diagnostic tests (RDT) have been postulated as a way to ensure access to malaria diagnosis in remote areas. Despite its widespread use, there are no field studies to evaluate the accuracy of the SD Bioline Malaria Antigen Pf/Pv in Colombia RDT. Objective: To evaluate the diagnostic accuracy of the SD Bioline Malaria Antigen Pf/Pv® RDT in two departments endemic for malaria, comparing diagnosis with thick film corrected with PCR. Materials and methods: A retrospective study was carried out to evaluate sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), concordance and sensitivity limits according to parasitemia ranges for the SD Bioline Malaria Antigen Pf/Pv ® test in Cordoba and Choco. The results were compared with microscopy corrected by PCR. Results: A total of 383 samples processed, 121 were positive (75 for P. vivax , 42 for P. falciparum and 4 for mixed infection) and 262 negative samples. P. vivax: sensitivity 92.0% (95% CI: 83.6-96.3), specificity 98.7% ( 95% CI: 96.7-99.5), PPV 94.5% (95% CI: 86.7-97.9), NPV 98.1% (95% CI: 95.8-99.1), Cohen´s kappa coefficient was 0.90 (0.80-1.00). P. falciparum: sensitivity 88.1% (95% CI: 75.0-94.8), specificity 97.9% (95% CI: 95.8-99.0), PPV 84.1% (95% CI: 70.6-92.1), NPV 98.5% (95% IC: 96.6-99.4), Cohen´s kappa coefficient 0.80 (95% CI: 0.70-0.90). Conclusions: The test performed well, being better for P. vivax as compared to P. falciparum. There are still difficulties of RDT to detect low parasitemias. The non amplification of Pfhrp2 and Pfhrp3 genes in two samples diagnosed as mixed infection, suggest a possible deletion of these two genes together.

Sentinel network for monitoring in vitro susceptibility of Plasmodium falciparum to antimalarial drugs in Colombia: a proof of concept

Drug resistance is one of the principal obstacles blocking worldwide malaria control. In Colombia, malaria remains a major public health concern and drug-resistant parasites have been reported. In vitro drug susceptibility assays are a useful tool for monitoring the emergence and spread of drug-resistant Plasmodium falciparum. The present study was conducted as a proof of concept for an antimalarial drug resistance surveillance network based on in vitro susceptibility testing in Colombia. Sentinel laboratories were set up in three malaria endemic areas. The enzyme linked immunosorbent assay-histidine rich protein 2 and schizont maturation methods were used to assess the susceptibility of fresh P. falciparum isolates to six antimalarial drugs. This study demonstrates that an antimalarial drug resistance surveillance network based on in vitro methods is feasible in the field with the participation of a research institute, local health institutions and universities. It could also serve as a model for a regional surveillance network. Preliminary susceptibility results showed widespread chloroquine resistance, which was consistent with previous reports for the Pacific region. However, high susceptibility to dihydroartemisinin and lumefantrine compounds, currently used for treatment in the country, was also reported. The implementation process identified critical points and opportunities for the improvement of network sustainability strategies.