An example system for detecting an analyte in a sample of a bodily fluid comprises a test chamber having at least one sidewall and configured to contain at least a portion of a bodily fluid sample, an excitation electromagnetic energy source configured to direct an energy source into the test chamber through the at least one sidewall and to induce a thermoelastic expansion in the one or more analytes, and a sensor configured to detect said thermoelastic expansion in the bodily fluid sample in the test chamber, the sensor configured to measure changes in optical reflectance that result from the thermoelastic expansion.