Psoriasis Tests & Diagnosis

May 7th 2016

Visual Examination

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. A primary care physician may be able to diagnose psoriasis. Your doctor may choose to refer you to a dermatologist or other specialist for a more precise diagnosis.

In some situations, a conclusive diagnosis is impossible based on visual examinations, alone. Additional tests might be necessary to diagnose psoriasis or any other possible skin conditions.

Skin Biopsy

The doctor might choose to perform a skin biopsy in order to rule out other possible skin conditions, sexually transmitted diseases, or infections. With a skin biopsy, the doctor may order a series of lab tests to determine whether certain bacteria, viruses, or fungi are present.

A doctor might also choose to perform an allergy test to determine whether your rash is the result of an allergic reaction to a food, plant, animal, or any other environmental conditions.

With a biopsy, the doctor will process a sample of your skin before viewing it under a microscope. The sampling technique and amount of skin removed will vary based the type of abnormality suspected. The skin sample may need to be placed in a sterile solution such as formaldehyde or in a sterile container, especially if there is a possibility of a bacterial or fungal infection.

Skin biopsies are common procedures that are used to diagnose conditions such as skin cancer, bacteria, or fungal infections.

General anesthesia is not required for skin biopsies. Most patients just need a local anesthetic. If you are about to have a skin biopsy, be sure that you tell your doctor whether you are taking any medications, especially steroids such as prednisone. Certain anti-inflammatory medications can change the way that your skin will look under a microscope.

Also let your doctor know if you are allergic to any medications or if you have problems relating to bleeding or clotting. You should also let your doctor know whether you are taking blood thinners that could cause a problem with clothing. You should also inform your doctor if there is a possibility that you might be pregnant.

White Flake of Skin

When the doctor conducts a test with or without a microscope, he or she will pull a white flake of skin. If blood appears, the skin is likely affected with psoriasis.

Process of Elimination

Psoriasis might also be diagnosed through process of elimination. If other similar-looking conditions have been ruled out, your doctor might explore psoriasis as a possibility. If you suspect psoriasis, you will need to be assertive and request that you receive the appropriate tests. Keep going back to the doctor, and seek second opinions so that you can get conclusive answers. Keep track of your symptoms so that you have additional information to pinpoint what's causing your condition.

Psoriatic Arthritis

If you have psoriatic arthritis, you'll experience joint swelling and pain. Problems will begin in the finger around the nail after a skin eruption. A doctor may choose to conduct a blood test in order to test for rheumatoid factor (RF), which detects rheumatoid arthritis. This type of test can help doctors understand whether other conditions are causing symptoms of arthritis.


If you are showing symptoms of arthritis, with or without psoriasis, the doctor may choose to conduct an X-ray in order to assess whether the bones have experienced any long-term damage. The X-ray cannot distinguish psoriatic arthritis from other types of arthritis: a doctor will need to assess all of your symptoms in order to form a complete picture.


Psoriasis is commonly misdiagnosed since it can resemble so many conditions like acne, arthritis, and sexually transmitted diseases. The condition can go undetected until symptoms become present. Symptoms vary from person to person and can range from mild to severe, so it's impossible to develop a "check list" of what causes psoriasis. The best way to receive an accurate diagnosis is to see a skin specialist.

Lab Tests

There are no blood tests or urine tests available to test for psoriasis. A doctor might order a blood test or urine test to rule out other possible skin conditions, rashes, or sexually transmitted diseases.

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