Towards noninvasive white blood cell count.

Despite rapid advances in diagnostic and imaging technologies, no clinical device for noninvasive monitoring of the immune system is currently available. The standard white blood cell count (WBCC), a key clinical measure for assessing patients' health, requires drawing blood, which poses inherent risks for secondary infection and anemia in vulnerable patient populations. In addition, the specialized equipment, expertise, and infrastructure are not always available in resource-poor settings. We present a method for noninvasive and label-free WBCC by imaging human oral mucosa using a miniaturized oblique back-illumination microscope (mOBM), together with an analytical pipeline for cell detection and quantification. In a pilot study involving 34 healthy subjects, we validated the ability of our system to detect and quantify circulating leukocytes and compared our image-based WBCCs with standard laboratory measurements. The ability to perform noninvasive WBCC will enable real-time assessment of immune status during infection and inflammation or in response to therapeutic intervention without repetitive blood sampling.