Can you get a sample of blood for a newborn screen from a baby's arm instead of their foot?

Yes. You can, but small quantities of blood are more easily and less apinfully obtained from the foot.
Theoretically yes. Blood is blood, but logistically tougher skin larger target and relative simplicity of getting a leg to stay still for a second to get a specimen support the continued use of heel sticks.
YES, BUT. Young infants are stingy with their little veins and often need to be stuck several times for those tests that require a vein sample. The foot draw is scary and looks barbaric, but is technically easier on both baby and the technician.Since the test does not require a direct vein sample, the foot wins out for practicality.