Final answer:
The flash in the syringe method of blood specimen collection refers to the appearance of blood in the barrel of the syringe.
Step-by-step explanation:
In the context of obtaining a blood specimen using the syringe method, the flash refers to the appearance of blood in the barrel of the syringe.
When the needle penetrates a vein, blood enters the barrel of the syringe, which indicates that the vessel has been successfully accessed.
It is important for healthcare professionals to observe the flash to ensure accurate collection of the blood specimen.
Learn more about blood specimen collection using the syringe method