Evaluation of haematological and volume, conductivity and scatter parameters of leucocytes for aetiological diagnosis of undifferentiated fevers.

Abstract

In this follow-up study, we aimed to establish the cut-off values of the volume, conductivity and scatter (VCS) parameters of leucocytes that significantly differ in dengue fever, malaria, scrub typhus and enteric fever, as described in our pilot study. A prospective observational case-control study was undertaken on patients with an established diagnosis of acute malaria (n=476), dengue fever (n=927), scrub typhus (n=425), bacterial sepsis (n=1598) or enteric fever (n=885) and the haematological and VCS data obtained by the Coulter LH 750 analyser were compared with controls. Malaria significantly altered the platelet count and plateletcrit. The cut-offs for the monocyte volume, lymphocyte volume, neutrophil volume, neutrophil volume distribution width, lymphocyte volume distribution width, monocyte volume distribution width and neutrophil conductivity distribution width had 90% negative predictive values (NPVs) for malaria. Except for the proportion of monocytes, lymphocyte scatter distribution width and platelet distribution width, a >70% positive (PPV) and negative predictive value (NPV) for dengue was noted in all the haematological and VCS parameters analysed. While the cut-offs determined in scrub typhus had a good (>80%) PPV and NPV, a significant difference was seen in neutrophil, monocyte and lymphocyte conductivities, but with low sensitivity, specificity, PPV and NPV in enteric fever. Aetiology-specific changes occur both in numbers as well as in VCS properties in acute fevers. Formulae and/or algorithms need to be utilized to realize the full potential of the VCS technology.