TABLE 6.

Criteria used for the identification of the triggering bacterium as a probable or possible cause of ReA^a

Bacterium	Criterion
Chlamydia	1. Probable ReA
	Chlamydia positive in urogenital smear plus symptomatic urethritis
	IgG ≥ 1/64 plus positive IgA or IgM plus Chlamydia positive in urogenital smear or symptomatic urethritis
	Antibody titers of 2 standard deviations (SD) above normal for IgG plus IgA or IgM plus symptomatic enteritis or Widal agglutination ≥ 1/320 (normal <1/60)
	2. Possible ReA
	Chlamydia positive in urogenital smear or IgG ≥ 1/64 plus positive IgA or IgM
Yersinia	1. Probable ReA
	Yersinia-positive stool culture
	Antibody titers of 3 SD above normal for IgG plus IgA or IgM
	Antibody titers of 2 SD above normal for IgG plus IgA or IgM plus symptomatic enteritis
	2. Possible ReA
	Antibody titers of 2 SD above normal for IgG plus IgA or IgM or Widal agglutination > 1/320 (normal, <1/160)
Salmonella	1. Probable ReA
	Salmonella-positive stool culture
	Antibody titers of 3 SD above normal for IgG plus IgA or IgM
	Antibody titers of 2 SD above normal for IgG plus IgA or IgM plus symptomatic enteritis
	2. Possible ReA
	Antibody titers of 2 SD above normal for IgG plus IgA or IgM
Campylobacter	1. Probable ReA
	Campylobacter-positive stool culture
	Antibody titers of 3 SD above normal for IgG plus IgA or IgM
	2. Possible ReA
	Antibody titers of 2 SD above normal for IgG plus IgA or IgM

^aAlways in the presence of an arthritis either asymmetrically or predominantly of the legs. For probable ReA, only one of the criteria has to be fulfilled. Data are from references 50, 71, 107, and 113.