Latent structure of irritable bowel syndrome symptom severity

Table 1 Latent correlations between validation criteria and the four factors of the Birmingham irritable bowel syndrome questionnaire according to a bifactor model

Validation criteria	Birmingham IBS questionnaire
	General factor	Constipitation	Diarrhea	Pain
Age (1 = female; 2 = male)	0.06	-0.13a	-0.21b	-0.27b
Gender	-0.20b	0.01	0.07	-0.39b
Fatigue severity scale	0.34b	0.07	0.01	0.13a
Pain sensitivity questionnaire	0.01	0.13b	0.09	0.23b
Somatoform dissociation questionnaire	0.36b	0.02	-0.01	-0.02

n = 875.

^aP < 0.05,

^bP < 0.01 vs control. WLSMV-estimation. Validation criteria are included into the model as manifest variables. Model fit is CFI = 0.99, RMSEA = 0.05. IBS: Irritable bowel syndrome.