Comparación entre metodologías para el diagnóstico microscópico de malaria / Comparison of methodologies for microscopic malaria diagnosis

Resumen Introducción. Como parte del plan de eliminación de la malaria en Colombia, se propuso desarrollar actividades enmarcadas en la línea de trabajo: "Mejorar el acceso y la calidad del diagnóstico de malaria". Objetivo. Comparar la metodología recomendada por la Organización Panamericana de la Salus con la utilizada en Colombia para el diagnóstico de la malaria. Materiales y métodos. Se recolectaron muestras y se prepararon 88 láminas para el diagnóstico de malaria, bajo diferentes tratamientos según los parámetros evaluados. Después de la lectura microscópica por duplicado, se hicieron los respectivos cálculos de varianza para todas las posibles comparaciones de coloración con los dos métodos usados (gota gruesa y gota gruesa combinada), según la coloración (Romanowsky modificado o Giemsa) y el resultado del recuento parasitario (500, 1.000, 5.000 y 10.000 parásitos/µl de sangre). Resultados. Se obtuvo un coeficiente kappa de Cohen de concordancia entre observadores de 0,923 (IC95% 0,768-1,0). Ninguno de los factores (A: coloración, B: metodología) o interacciones (AB) tuvo un efecto estadísticamente significativo sobre los resultados, con un 95 % de nivel de confianza. Conclusión. Según los resultados obtenidos, la observación de dos gotas gruesas en una misma lámina y el uso de la tinción modificada de Romanowsky, continúa siendo una metodología adecuada para el diagnóstico de malaria en Colombia, por sus características técnicas, de almacenamiento, bajo costo y cuidados de uso.

Abstract Introduction: As part of the pre-elimination plan for malaria in Colombia, it has been proposed to develop activities within the line of work: "Improve access and quality of malaria diagnosis". Objective: To compare the methodology recommended by PAHO/WHO with that used in Colombia for the diagnosis of malaria. Materials and methods: Samples were collected and 88 slides were prepared for malaria diagnosis, under different scenarios according to the parameters to be evaluated. After duplicate mycroscopic reading, the respective variance calculations were performed for all possible staining comparisons with the two methods used (thick smear, combined thick smear), according to the staining (modified Romanowsky or Giemsa), with the result variable being the parasite density (500, 1,000, 5,000 and 10,000 parasites/µl of blood). Results: A Cohen kappa index of inter-rater agreement of 0.923 (95% CI: 0.768-1.078) was obtained. None of the factors (A: stain, B: methodology) or interactions (AB) had a statistically significant effect on the results with a 95% confidence level. Conclusion: Based on the results of the study, the preparation of two thick smears in the same slide stained with the modified Romanowsky stain is a suitable methodology for the diagnosis of malaria in Colombia, due to its technical characteristics, of storage, low cost, use and care.

Uso de paneles de láminas estandarizadas para la evaluación de competencias en el diagnóstico microscópico de malaria en la Amazonía Peruana / Use of standardized blood smear slide sets for competency assessment in the malaria microscopic diagnosis in the Peruvian Amazon

Objetivos. Evaluar la competencia de los microscopistas en el diagnóstico de la malaria mediante paneles de láminas estandarizados en la Amazonía peruana. Materiales y métodos. Estudio transversal, realizado entre los meses de julio y septiembre de 2007, en 122 establecimientos de salud de primer nivel de atención de la Amazonía peruana. En el marco del Proyecto PAMAFRO, se evaluó las competencias en el diagnóstico de malaria en 68 microscopistas sin experiencia (

Objectives. To assess the competency of microscopists for malaria diagnosis using standardized slide sets in the Peruvian Amazon. Material and methods. Cross-sectional study carried out in 122 first level health facilities of the Peruvian Amazon, between July and September 2007. Within the frame of the project "Control Malaria in the border areas of the Andean Region: A community approach" (PAMAFRO), we evaluated the malaria diagnosis performance in 68 microscopists without expertise (< 1 year of expertise) and 76 microscopists with expertise (> 1 year) using standardized sets of 20 blood smear slides according to the World Health Organization (WHO) recommendations. A correct diagnosis (correct species identification) was defined as "agreement", a microscopist was qualified as an "expert" if they have an agreement ≥90 percent (≥ 18 slides with correct diagnosis), as a "referent" with an agreement between 80 percent and <90 percent, "competent" if they are between 70 and <80 percent and "in training" if they have <70 percent. Results. Microscopists with expertise (68.6 percent) had more agreement than those without expertise (48.2 percent). The competency assessment was acceptable (competent, referent, or experts levels) in 11.8 percent of the microscopists without expertise and in 52.6 percent from those with expertise. The agreement was lower using blood smear slides with P. falciparum with low parasitaemia, with P. malariae and with mixed infections. Conclusions. Is the first assessment, we found only one of three microscopists from the Peruvian Amazon is competent fro malaria diagnosis according to the WHO standards. From this baseline data, we have to continue working in order to improve the competency assessment of the microscopists within the frame of a quality assurance system.