Re-evaluation of the pathergy test in Behçet's disease.

A positive pathergy test in patients with Behçet's disease has been accepted as a diagnostic criterion by many authors, but in recent years it has been claimed that the test has a decreased positivity. We have examined the test in 92 proven cases of Behçet's disease, using 20G and 26G disposable needles and evaluated them after 48 h. Maximum positivity was found to be 65% when we used needles of size 0.9 mm (20G), but the reactivity was considerably less when 0.3 mm diameter (26G) needles were used. The disposable needles used nowadays are less traumatic to initiate the reaction than were the non-disposable ones used in the pre-AIDS era.