With regard to ethnic indicators, the cited article is not the best one, and the current description is misleading. Recent research suggests that Ashkenazi Jews are, in fact, carriers of FMF at the rate of approximately 20 percent. See "Mutation and Haplotype Studies of Familial Mediterranean Fever Reveal New Ancestral Relationships and Evidence for a High Carrier Frequency with Reduced Penetrance in the Ashkenazi Jewish Population", Am. J. Hum. Genet. 64:949–962, 1999, <http://www.journals.uchicago.edu/AJHG/journal/issues/v64n4/980834/980834.web.pdf>.
I have not found this recommended in any of the current literature. Ben-Chetrit et al have presented contradictory findings in 1990 in a letter to the editor (Lancet). There does not seem to have been much discussion on the subject since.