How is Pso diagnosed?

Your GP (General Practitioner) may refer you to a dermatologist, a specialist skin doctor, who will probably be able to diagnose your psoriasis (Pso) just by looking at it.1 However, if he or she thinks it is necessary, a biopsy (a small skin sample) may also be taken to confirm the diagnosis and rule out other diseases.1 If your Pso was triggered by a throat infection, a swab carried out on the throat can identify the presence of bacteria,2,3 and you may be prescribed an antibiotic.

Up to 30% of people with Pso also suffer from psoriatic arthritis, a form of arthritis that affects the joints.5 If you have Pso with joint pain, you may be referred to a rheumatologist for diagnosis (confirmation), monitoring and treatment.1,5,6 


If you notice joint pain that doesn’t go away, tell your doctor6


Your dermatologist may keep an eye on your skin symptoms using one or more of the following scales:


  • The Psoriasis Area and Severity Index rates how much of the body is affected and how severe the Pso. It combines the severity and surface area for six regions of the body, assigning scores ranging from 0 to 72. Usually, the higher your score, the lower your quality of life.7


  • The Body Surface Area scale measures how much of the body surface area is affected by the psoriasis, using the size of one hand to represent 1% of your body’s surface area.8


  • The Nail Psoriasis Severity Index divides the nail into quadrants and assesses the psoriasis in both the nail itself and in the nail bed just beneath it.9


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1.    NHS. Psoriasis overview. Available at: Accessed: June 2020.
2.    National Psoriasis Foundation. Guttate psoriasis. Available at: Accessed: June 2020.
3.    British Association of Dermatologists patient hub; Psoriasis: an overview. Available at: Accessed: June 2020.
4.    DermNet NZ. Guttate psoriasis. Available at: Accessed: June 2020.
5.    PAPAA. Psoriasis: a simple explanation. Available at: Accessed: June 2020.
6.    National Psoriasis Foundation. About psoriatic arthritis. Available at: Accessed: June 2020.
7.    WebMD. Skin problems and treatments: psoriasis. How severe is your psoriasis? Available at: Accessed: June 2020.
8.    Walsh JA, et al. Psoriasis (Auckl). 2018; 8:65–74.
9.    GP notebook. NAPSI. Available at: Accessed: June 2020.