Psoriasis is a chronic condition that causes scaly, inflamed patches of skin. It may cause a person’s nails to become thick, ridged, or pitted.

To learn whether psoriasis or another condition is causing someone’s symptoms, a doctor will examine their skin and nails and ask them about their symptoms and medical history. Sometimes, they may also order one or more diagnostic tests.

After diagnosing psoriasis, a doctor may order tests to learn whether certain treatments are safe and check for signs of treatment side effects. They may also order tests to learn whether someone has developed psoriatic arthritis, a joint condition that affects an estimated 30% of people with psoriasis.

The infographic below describes several tests that someone with psoriasis might receive.