Improvement of the Detection of Plasmodium vivax by Using iRBC QFlag Values from the Sysmex Hematology Analyzer XN-1000 Coupled with Platelet Count

Abstract

Plasmodium vivax malaria is the most prevalent in Thailand, and the prompt and accurate detection of the infection are crucial for controlling the disease pandemic. This study aimed to study the efficiency in the diagnosis of P. vivax malarial infection by using the “iRBC QFlag”, a novel parameter developed and obtained from the Sysmex XN-1000 automated analyzer coupled with the platelet count. This is an experimental comparative research was conducted between August 1^st, 2022 and October 31^st, 2023. From the total of 3,818 samples, there were 1,279 cases with request for CBC and thick film tests, while 2,539 cases with request for CBC, but not thick film test. The iRBC QFlag (≥ 10 AU) and platelet count (< 140 x 10⁹/L) were used to detect P. vivax in blood samples, and the area under the ROC curve was at 0.991 and 0.981, respectively. When using combination of iRBCQFlag (≥10 AU) and platelet count, the sensitivity, specificity, and positive and negative predictive values were 97, 100, 100 and 99.8, respectively. In conclusion, the sensitivity of P. vivax detection increased to 97% when the iRBC QFlag value for positive cutoff was decreased and applied with the platelet counts. This finding suggest that when the value of iRBC QFlag ≥ 10 AU and PLT < 140 x 10⁹/L or iRBC QFlag value of 20-300 AU and PLT ≥ 140 x 10⁹/L, there may be the infection of P. vivax malaria, which should be confirmed by the thick blood film method.