1. A method of classifying white blood cells (WBCs) in a biological sample on a substrate, the method comprising: acquiring, by an image acquisition device, a plurality of images of a first location on the substrate; identifying one or more non-WBC objects in the plurality of images, the non-WBC objects including one of more of platelets, clumps, giant platelets, and micromegakaryocytes; determining, by one or more processing devices using a first classification process, that a given object in the plurality of images is associated with a first classification group selected from a set of multiple WBC classification groups, wherein the first classification process is based on a first set of features, and wherein the one or more non-WBC objects are excluded from the first classification process; determining, by the one or more processing devices using a second classification process, that the given object is associated with a second classification group, wherein the second classification process is based on a second set of features different from the first set of features; in response to determining that the given object is associated with the second classification group, changing a classification of the given object; and presenting, on a user interface, a representation of the given object and the corresponding classification, wherein the first classification process and the second classification process are performed by a multi-stage classifier, wherein at least one stage of the multi-stage classifier includes a linear discriminant analysis (LDA) based classifier, and at least another stage of the multi-stage classifier includes a Bayesian classifier.