Development and validation of a registry-based definition of eosinophilic esophagitis in Denmark

Table 1 Characteristics of the case definition development set (2006-2007) and validation set (2008-2009) n (%)

	Development set (2006-2007)				Validation set (2007-2008)
	Overall (n = 51)	EoE cases (n = 21)	Sensitive definition (n = 31)	Specific definition (n = 9)	Overall (n = 49)	EoE cases (n = 24)	Sensitive definition (n = 26)	Specific definition (n = 6)
Age, yr (mean ± SD)	42 ± 19	35 ± 16	40 ± 18	38 ± 19	48 ± 21	42 ± 15	49 ± 19	49 ± 19
Male	38 (75)	16 (76)	22 (71)	7 (78)	36 (73)	20 (83)	21 (81)	4 (67)
Dysphagia	24 (47)	18 (86)	28 (90)	8 (89)	19 (39)	16 (67)	18 (69)	3 (50)
Esophageal foreign body	15 (29)	11 (52)	14 (45)	3 (33)	8 (16)	2 (8)	4 (15)	1 (17)
Rhinitis/sinusitis	5 (10)	2 (10)	2 (6)	1 (11)	0 (0)	0 (0)	0 (0)	0 (0)
Asthma	3 (6)	1 (5)	1 (3)	0 (0)	2 (4)	2 (8)	2 (8)	1 (17)
PPI use	38 (75)	17 (81)	21 (68)	9 (100)	33 (67)	12 (50)	21 (81)	6 (100)
Maximum eosinophil count, eos/hpf (mean ± SD)	71 ± 53	103 ± 54	84 ± 58	93 ± 83	68 ± 71	77 ± 62	60 ± 35	43 ± 31

EoE: Eosinophilic esophagitis; PPI: Proton-pump inhibitor; eos/hpf: Eosinophils per high-power field.

Table 2 Case definition algorithm

For both the sensitive and the specific case definitions:

(1) Include all patients with systematized nomenclature of medicine M47150 (finding of tissue eosinophil) and T62xxx (esophageal biopsy)

(2) Exclude patients if they have one of the following International Classification of Diseases-10 codes occurring at any time:

B20.x - human immunodeficiency virus

C15.x - malignant neoplasm of esophagus

C16.0 - malignant neoplasm of cardia

C92.x - myeloid leukemia

C94.x - other leukemias of specialized cell type

C96.x - other and unspecified lymph/heme malignancies

K22.0 - achalasia

K50.x - Crohn’s disease

K52.8 - eosinophilic gastritis/duodenitis

T28.1 - burn of esophagus

T28.6 - corrosion of esophagus

(3) Include patients if one of the following International Classification of Diseases-10 codes is present at or before the date of the procedure:

K22.2 - esophageal obstruction

K30.9 - dyspepsia

P92.x - feeding problems of the newborn

R07.x - pain in throat and chest

R10.x - abdominal pain

R11.x - nausea/vomiting

R12.x - heartburn

R13.x - dysphagia

T18.0 - foreign body in mouth

T18.1 - foreign body in esophagus

T18.2 - foreign body in stomach

T18.9 - foreign body in genitourinary tract unspecified

T98.0 - sequelae of foreign body entering through a natural orifice

Additional requirement for the specific case definition:

(4) Include patients if there is a proton-pump inhibitor prescription (A02BCxx) or H2RA prescription (A02BAxx) within 2 mo of esophageal biopsy date, up to and including 2 d prior to the esophagogastroduodenoscopy

Table 3 Sensitivity and specificity of the case definitions¹n (%)

	Development set		Validation set
	Sensitive definition	Specific definition	Sensitive definition	Specific definition
Sensitivity	90 (90)	38 (38)	88 (88)	21 (21)
Specificity	60 (60)	97 (97)	80 (80)	96 (96)

¹Sensitivity: Number of true positive eosinophilic esophagitis (EoE) cases identified by the case definition divided by the total number of reference standard EoE cases; Specificity: Number of true negative subjects identified by the case definition divided by the total number of subjects without EoE.