How to diagnose psoriasis?

Michael Rosenberg
Michael Rosenberg

Specializes in translating complex information into readable, engaging content.

Autoimmune diseases, like psoriasis, can cause severe discomfort and may develop into life-threatening complications if not treated immediately. To avoid such complications, the patients of such autoimmune diseases must be aware of their diagnosis methods. So, the same applies to people who have psoriasis. So,nowadays, there are multiple ways to diagnose psoriasis. Each technique involved in the diagnosis of psoriasis has its benefits and drawbacks. Here, the current article will discuss the diagnosis methods in detail, focusing on:

  • Medical Review
  • Self Checks
  • Physical Examinations
  • Formal Lab Tests
  • PASI Classifications
  • Differential Diagnosis.

how to diagnose psoriasis

Medical Review

Usually, the essential tool in determining the development of any autoimmune disease is the patient’s medical history. If the medical records suggest sudden, rapid, and unexplained changes, the medical practitioner may determine that the patient suffers from an autoimmune disease. However, the case of psoriasis is different as the doctor won’t suggest blood tests or imaging studies help in the diagnosis of psoriasis. Instead, other methods dedicated to skin treatment are used to diagnose the condition. However, for a patient with no instability in their medical records, those methods below are the standard route for diagnosis.


Try to notice any unusual changes in your skin. If any changes suggest signs or symptoms of psoriasis, contact your doctor or dermatologist immediately for a formal skin diagnosis. Thus. the most common symptoms for all types of psoriasis include red patches on the skin that may be shiny, the development of thick and inflamed scales on the skin patches, and pus-filled blisters. Usually, these signs appear on the fold areas of your skin, including your armpits, groin, and the area around your genitals. Also, it may appear on your chest and scalp as well.

Physical Examination

A trained and experienced dermatologist can diagnose psoriasis based on the appearance of your skin. If so, a simple physical examination with a dermatoscopy is the preferred method to diagnose psoriasis. Different types of psoriasis may also lead to non-dermatological symptoms, including uveitis, blepharitis and psoriatic arthritis, etc. 

In addition to the physical exam, the doctor will consider the patient’s medical history to locate any signs of:

  • Familial history of psoriasis or skin disorders
  • Strep throat infection
  • Any recent vaccines
  • Immunosuppressive diseases
  • Any other autoimmune disorder.

Formal Lab Tests

In some cases, the rash itself may not help in diagnosing psoriasis sufficiently. Therefore, the doctor may recommend a microscopic, histological evaluation of the skin tissue. If so, the patient would require skin biopsy, including minimally invasive punch biopsy. The doctor may perform the test in his office using a local anesthetic. Once obtained, hematoxylin-eosin is used to stain the tissue sample, differentiating the skin cells under the microscope. So, if the person has psoriasis, the skin cells will appear acanthotic.

PASI Classification

Diagnosing psoriasis is not the only aspect required to provide an effective treatment. Instead, the severity of the condition has to be determined using an accepted scale called Psoriasis Area and Severity Index (PASI). The severity of the symptoms in each body area is determined and ranked. The scale includes:

  • Redness or Erythema scaling between 0 and 4.
  • Induration or thickness scaling between 0 and 4.
  • Desquamation scaling between 0 and 4
  • Percentage of skin involved scaling between 0% and 100%

Differential Diagnoses

In some cases, it is possible to mistaken psoriasis for some other skin condition. If so, other tests may be performed to distinguish the condition. Moreover, the diagnosis may involve tests to determine atopic dermatitis, keratoderma blennorrhagicum, contact dermatitis, lichen simplex chronicus, lupus, and onychomycosis.


To conclude, diagnosing psoriasis is important to treat the condition effectively. So, consult your dermatologist today if you see any symptoms of the condition. Let us know in the comments section if the article was helpful.

Read more about psoriasis:

What are psoriasis types and symptoms?

What are the early signs of psoriasis?


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