DERMATOLOGY

Definition

The pathergy test used in the diagnosis of Behçet's disease is defined as applying a 45-degree (oblique) picture to the superficial area of ​​the forearm that does not contain veins and hair, with a thick-tipped needle, and evaluation of a papule, pustule or papulopustular lesion that may develop in this area after 24-48 hours.

Application

The inner surfaces of the forearms are wiped with alcohol cotton. Disposable syringe tips (20 G) are inserted into the skin at a 45-degree angle (obliquely) after being dipped several times into their plastic caps and slightly blunted. Since it is necessary to reach the dermis, it is appropriate to insert the needle about 5 mm into the skin. The process is applied bilaterally. Three picures are made on each arm, approximately 3 cm apart. A ring with a diameter of 1-2 cm is drawn around the picures with a pencil and their location is determined.

Comments

The formation of erythematous papules or pustules within 24-48 hours is considered positive.

Notes

The information and consent form should be read and signed by each patient.

A negative pathergy test does not eliminate the diagnosis of Behçet's disease. Although its positivity is helpful in diagnosis, its sensitivity is low. The pathergy test is positive in approximately half of those with Behçet's disease. Its specificity is higher (pathergy test is negative in a significant proportion of patients without Behçet's disease).

It is appropriate to discontinue anti-inflammatory or immunosuppressive drugs prior to testing.

There is no international standard for the number of picures to be made in the pathergy test. However, there are opinions that test positivity may increase with an increase in the number. Because of the possibility that disposable needles may not be sufficiently traumatized, it may be appropriate to blunt the needles using the method described above.