Negative for ra- dr suspects pa due to occasional rash on elbows. Rash hasn't appeared for several mths. Is there any other was to diagnose psoriasis?

Skin biobsy ,Flake. There are no lab tests or blood tests available to confirm or deny the presence of psoriasis. Instead, a doctor must examine the skin and nails closely, sometimes analyzing dry skin under a microscope.Your doctor may take a small sample of skin (biopsy) that's examined under a microscope to determine the exact type of psoriasis and to rule out other disorders.