A biological fluid sampling transfer device adapted to receive a multi-component blood sample is disclosed. After collecting the blood sample, the biological fluid sampling transfer device is able to separate a plasma portion from a cellular portion. After separation, the biological fluid sampling transfer device is able to transfer the plasma portion of the blood sample to a point-of-care testing device. The biological fluid sampling transfer device also provides a closed sampling and transfer system that reduces the exposure of a blood sample and provides fast mixing of a blood sample with a sample stabilizer. The biological fluid sampling transfer device is engageable with a blood testing device for closed transfer of a portion of the plasma portion from the biological fluid sampling transfer device to the blood testing device. The blood testing device is adapted to receive the plasma portion to analyze the blood sample and obtain test results.