Commercial flow cytometers are sophisticated analytical instruments extensively used in research and clinical laboratories. However, they do not meet the challenging practical requirements for point-of-care (POC) testing. PARC has demonstrated a new optical detection technique termed spatially modulated emission that delivers high signal-to-noise discrimination without precision optics to enable a flow cytometer that can combine high performance, robustness, compactness, low cost, and ease of use. The detection technique has been extensive evaluated with measurements of absolute CD4+ and percentage CD4 counts in human blood. To benchmark our system we performed a direct one-to-one comparison of measurements on the same samples with a commercial instrument (BD FACSCount) and obtained excellent agreement for both absolute CD4 and percentage CD4. We have assembled the first generation of a compact (~5x3x2 inch), single-parameter, flow cytometer based on the spatial modulation technique which uses a pin photodiode for detection rather than a PMT or APD. The prototype was assembled with off-the-shelf components (total cost of all parts <$250). The whole unit is battery powered. Measurements of the sensitivity and dynamic range of the prototype were conducted with 3.8-um ultra-rainbow calibration beads (Spherotech) and yielded a detection limit ~10^3 MEPE, which meets the needs for a wide range of bio-particle-detection applications.
Kiesel, P.; Beck, M.; Johnson, N. M. Hand-held flow cytometer for point of care CD4 testing. Special Focus Session on BioChip Physics - Fundamental Detection Physics and Lab on a Chip, APS March Meeting; 2010 March 15-19; Portland, OR.