1. A system for determining a presence of an analyte in blood, the system comprising: at least one memory storage medium configured to store a plurality of images of a sample slide, the plurality of images including, a plurality of fields-of-view, each including a unique x and y coordinate of the sample slide; and a plurality of focal planes, each having a unique z coordinate of the sample slide; at least one processor operably coupled to the at least one memory storage medium, the at least one processor being configured to, determine and apply a white balance transform to each of the plurality of images effective to produce a plurality of color-corrected images; determine and apply an adaptive grayscale transform to each of the plurality of images to provide an adaptive grayscale intensity image for each of the plurality of images; detect and identify one or more candidate objects in the color-corrected images and the adaptive grayscale intensity images, and the at least one processor is further configured to, perform an adaptive thresholding operation on the adaptive grayscale intensity images and output one or more candidate objects based thereon; cluster the one or more detected candidate objects into clusters including one or more adjacent candidate objects per cluster and associate clusters of detected candidate objects indicating that a cluster of one or more adjacent candidate objects are a single candidate object and output locations of the clusters of one or more adjacent candidate objects, the locations including one or more image patches containing the one or more adjacent candidate objects; locate the focal plane having a best focus for each single candidate object; determine attributes of each single candidate object in the focal plane having the best focus for each single candidate object; filter each single candidate object based at least in part on one or more determined attributes; and extract and output one or more image patches each containing at least one filtered single candidate object of the one or more candidate objects.