Tests aren't usually needed. But one or more of the following tests may be done:
- BiopsyBiopsy. If it is hard to diagnose the condition by looking at your skin, your doctor may remove a small skin sample and send it to a lab for analysis.
- X-raysX-rays. If you have joint pain, X-rays may be taken to look for psoriatic arthritis.
- Blood test. It can help rule out other forms of arthritis.
- Throat cultureThroat culture. If your doctor thinks you may have guttate psoriasis, he or she may want to check for strep throat.
- KOH testKOH test. Sometimes this skin test is done to rule out a fungal infection.