More than a drop of blood: the paradigm shift of a large-volume capillary sample for point-of-care clinical diagnostics.

The validation of a large-volume fingerstick sample for the newly Food and Drug Administration-authorized Xpert HCV test has created an important precedent for the use of a large-volume capillary blood sample for point-of-care (POC) testing. This advance opens the door to the development and deployment of a wide range of POC tests utilizing large-volume capillary samples, including tests that require larger sample volumes for detection of low-concentration analytes. Multiple tools for production and collection of large-volume capillary samples now exist, including many tools designed for yielding blood from capillaries in the upper arm. Most of these tools yield blood that demonstrates excellent concordance with venous blood on testing across a range of analytes, though analytes like potassium and platelets remain challenging for the arm-based tools, and data for molecular analytes are limited overall. Tools capable of separating liquid plasma from large-volume capillary whole blood samples for POC testing remain an elusive but critical goal. Understanding the regulatory expectations for pairing large-volume sample production tools and collection containers with POC testing devices will facilitate both uptake of large-volume collection strategies and POC blood test development, particularly because allowing multiple POC tests to be performed from one large-volume capillary sample would substantially improve the patient experience. Large-volume capillary blood collection is a new frontier key to the future of POC diagnostics.