A microfluidic sample analyzer comprising: a housing; an opening in the housing configured to receive a cassette having at least one channel with a fluid sample therein and at least one microfluidic channel having across-sectional dimension of less than 1 mm, wherein the housing includes a component configured to interface with a mating component on the cassette to detect the cassette withinthe housing; a pressure-control system positioned within the housing, the pressure-control system configured to pressurize the at least one channel in the cassette to move the sample through the at least one channel, wherein the pressure-control system includes a vacuum source, a manifold configured to couple the vacuum source to the at least one channel in the cassette, a pressure sensor configured to measure the pressure in the manifold, and a valve positioned between the vacuum source and the at least one channel; an optical system positioned within the housing, the optical system including a plurality of light sources and a plurality of detectors spaced apart from the plurality of light sources, wherein the light sources are configured to pass light through the cassette when the cassette is inserted into the sample analyzer and wherein the detectors are positioned opposite the light sources to detect the amount of light that passes through the cassette; wherein the plurality of light sources includes at least a first light source and a second light source adjacent the first light source, wherein the first light source is configured to pass light through a first measurement zone of the cassette and the second light source is configured to pass light through a second measurement zone of the cassette adjacent the first measurement zone a housing; an opening in the housing configured to receive a cassette having at least one channel with a fluid sample therein and at least one microfluidic channel having across-sectional dimension of less than 1 mm, wherein the housing includes a component configured to interface with a mating component on the cassette to detect the cassette withinthe housing; a pressure-control system positioned within the housing, the pressure-control system configured to pressurize the at least one channel in the cassette to move the sample through the at least one channel, wherein the pressure-control system includes a vacuum source, a manifold configured to couple the vacuum source to the at least one channel in the cassette, a pressure sensor configured to measure the pressure in the manifold, and a valve positioned between the vacuum source and the at least one channel; an optical system positioned within the housing, the optical system including a plurality of light sources and a plurality of detectors spaced apart from the plurality of light sources, wherein the light sources are configured to pass light through the cassette when the cassette is inserted into the sample analyzer and wherein the detectors are positioned opposite the light sources to detect the amount of light that passes through the cassette; wherein the plurality of light sources includes at least a first light source and a second light source adjacent the first light source, wherein the first light source is configured to pass light through a first measurement zone of the cassette and the second light source is configured to pass light through a second measurement zone of the cassette adjacent the first measurement zone