Factors influencing the efficiency of malaria rapid tests; Paracheck-Pf and OptiMAL-IT

Abstract

This study evaluated the influence of temperature and humidity to the efficiency of 2 malaria rapid diagnostic tests (MRDT); OptiMal - IT and Paracheck - Pf. Five exposure conditions were 35 °C, 40 °C, 45 °C, 28 - 37 % relative humidity, 80 - 90% relative humidity and control (4 - 7 °C). In each exposure, 3 standards; positive Plasmodium falciparum, positive P. vivax and negative were evaluated. The parasite densities of the positive controls were in the range of 500-1,000/µL which were confirmed by the previous studies as low density but with high accuracy for 2 types of the diagnostic tests. Semi-nested polymerase chain reaction (PCR) based on the detection of small subunit ribosomal ribonuclei acid (SSU rRNA) gene was exploited as gold standard for malaria species confirmation. Result revealed that humidity had no influence on the efficiency of 2 diagnostic test kits MRDTs. High temperature of more than 40 °C affected the diagnosing efficiency of OptiMAL - IT more than Paracheck - Pf. Storing the test kits at 40 C for 5 days resulted in declining of the efficiency of OptiMAL - IT from 100 to 83.33 compared to from 100 to 94.44% of Paracheck - Pf. The exposure of the test kits to 45 °C for 5 days reduced the efficiency of OptiMAL - IT from 96.66 to 77.78 and Paracheck - Pf from 100 to 88.89 with high frequency of false positive, false negative and cross reaction resulting the decline sensitivity and specificity. Storing MRDT at 4 – 7 °C for 5 days affected the average diagnostic test of more than 95%. Our results suggest that suitable storage temperature was at 4 – 7 °C. Transportation and storage temperature in fields/remote areas should be less than 35 °C. However this study was carried out with short period of time, continuation of the study to 1 year will give strong evidence for improving the logistic system.