Prevalence of anal fistula in the United Kingdom

Table 3 Prevalence of anal fistula with Crohn’s disease

		2014	2015	2016	2017
Prevalence of AF, n		252	212	174	142
Prevalence of AF, n/10000 patients		0.52	0.50	0.49	0.45
Gender	Female, n (%)	66 (43.3)	53 (42.4)	51 (46.8)	42 (43.8)
Age	0-19, n (%)	###	###	###	###
	20-39, n (%)	115 (45.6)	96 (45.3)	75 (43.4)	79 (55.6)
	40-59, n (%)	89 (35.3)	81 (38.2)	73 (42.2)	45 (31.7)
	60-79, n (%)	32 (12.7)	23 (10.8)	16 (9.2)	13 (9.2)
	80+, n (%)	###	###	###	###
Standardization to
	UK (95%CI)	0.51 (0.45-0.57)	0.50 (0.43-0.56)	0.48 (0.41-0.55)	0.44 (0.37-0.52)
	EU (95%CI)	0.52 (0.45-0.58)	0.50 (0.43-0.57)	0.48 (0.41-0.56)	0.44 (0.37-0.51)
Direct AF Read codes1
Prevalence of Direct AF, n		149	125	109	96
Prevalence of Direct AF, n/10000 patients		1.31	1.30	0.31	0.30
Standardization to
	UK (95%CI)	0.30 (0.25-0.35)	0.29 (0.24-0.34)	0.30 (0.24-0.36)	0.30 (0.24-0.36)
	EU (95%CI)	0.30 (0.26-0.35)	0.29 (0.24-0.35)	0.30 (0.25-0.36)	0.30 (0.24-0.36)
Indirect AF Read codes2
Prevalence of Indirect AF, n		147	125	102	70
Prevalence of Indirect AF, n/10000 patients		0.30	0.30	0.29	0.22
Standardization to
	UK (95%CI)	0.30 (0.25-0.34)	0.29 (0.24-0.34)	0.28 (0.23-0.34)	0.22 (0.17-0.27)
	EU (95% CI)	0.30 (0.25-0.35)	0.29 (0.24-0.35)	0.28 (0.23-0.34)	0.22 (0.17-0.27)

AF: Anal fistula; n: Number; CI: Confidence interval; UK: United Kingdom; EU: European Union;

¹Direct codes: Read codes directly identifying anal fistula (e.g., anal fissure and fistula, and fistula-in-ano);

²Indirect codes: Read codes identifying procedures or surgeries related specific to anal fistulas (e.g., excision of fistula in ano, and anal fistula operations); One patient can have multiple Direct and Indirect anal fistula codes; ### masking due to small patient numbers (n: 1-5).