Your physician can mostly identify Psoriasis based on the presenting signs and symptoms and examination of the lesions. Special tests are usually not required for this.

However, if it is difficult to confirm the diagnosis, he may take a small sample of your skin (biopsy) to be examined under the microscope at a laboratory. This helps to confirm the diagnosis as well as to rule out other similar-looking conditions.

In case of involvement of joints, X-ray of the affected joint may be taken to assess the degree of damage occurred to the joint as well as to monitor the progress of the illness. Certain blood tests may also be required to rule out other forms of joint diseases.

Throat culture may be required to look for streptococcal infection in cases of guttate psoriasis.

Certain conditions that may have an appearance similar to psoriasis include:

Eczema

Seborrheic dermatitis

Lichen planus

Pityriasis rosea

Ringworm (fungal infection / tinea corporis)

The prognosis of psoriasis is largely based on the severity of the illness. The National Psoriasis Foundation defines guidelines for diagnosing the severity of cases:

The palm of hand equals 1% of total skin area of the body

Mild Psoriasis is that which affects less than 3% of the body

Psoriasis is of moderate intensity if it affects 3 to 10% of the body

More than 10% of the body affection is considered severe

As per International Medical Protocols, the disease is said to be cured if the patient has no symptoms for five consecutive years.