Using an inertial focusing approach, this technology detects rare leukemic blast cells from blood samples. A patient’s blood sample is first collected, and red blood cells are lysed. The sample is then loaded into the inlet reservoir of a microfluidic biochip. Here, a net force that is comprised of net internal lift force and dean drag force is exerted onto the blood sample in a closed-loop spiral microchannel. Non-target cells, such as white blood cells, encounter a different net force than blast cells, which have a higher nuclear-to-cytoplasmic ratio. The differential net force allows distinct cell types to form separate focused streams within the microchannel. Strategically placed bifurcation points within the microchannel enable the sorting of cells undergoing differential net forces into separate outlet reservoirs. The isolated blast cells can then be further evaluated by flow cytometry and histopathology.