Evaluation of the LH780 hematology analyzer for detection and therapeutic monitoring of malaria: Cross-reactivity with nucleated RBCs

Abstract

We evaluated the diagnostic usefulness of the LH780 Coulter blood cell counter for detection and therapeutic monitoring of malaria including cross-reactivity with nucleated RBC (NRBC) samples. A total of 405 patients (43 patients with Plasmodium vivax malaria and the control group of 120 healthy subjects, 111 patients with fever, and 131 patients with NRBCs) were analyzed with routine CBC using the LH780. We analyzed the CBC results according to three selected parameters: an abnormal peak in the WBC histogram before 35fL, the presence of red dots in the nonwhite cell zone of 2D WBC Diff Dataplot, and platelet-related flags suggesting platelet clumps or giant platelets. Of the 43 malaria samples collected at diagnosis, an abnormal peak (≥2.2mm) was present in 93.0% (95% confidential interval (CI), 80.9–98.5%). Of all samples, 97.7% (95% CI, 87.7–99.9%) exhibited red dots, and platelet-related flags were observed in 81.4% (95% CI, 66.6–91.6%). The specificity of these three selected parameters was 83.1% (95% CI, 78.9–86.9%), 77.3% (95% CI, 72.7–81.6%), and 90.1% (95% CI, 86.5–92.9%), respectively. The abnormal peak (≥2.2mm) showed moderate correlation with parasite level (r=0.79). The three selected LH780 parameters were useful for identifying malaria in healthy subjects and febrile patients, but unsatisfactory for discriminating malaria in NRBC samples. The parameters showed a substantial proportion of false positives in the NRBC group, ranging from 26.7% to 49.6%. Therefore, microscopic confirmation will be necessary for application of these parameters for malaria screening and treatment monitoring.