Diagnostic and clinical significance of antigen-specific pancreatic antibodies in inflammatory bowel diseases: A meta-analysis

Table 1 Search strategy for PubMed and Cochrane-CENTRAL

Database	Key words
PubMed
No. 1	Anti-glycoprotein 2 antibody
No. 2	"Anti-glycoprotein 2 antibody"
No. 3	Anti-glycoprotein 2 antibody [Text Words]
No. 4	Autoantibodies to glycoprotein 2
No. 5	"Autoantibodies to glycoprotein 2"
No. 6	Autoantibodies to glycoprotein 2 [Text Words]
No. 7	"Glycoprotein 2 autoantibodies"
No. 8	Glycoprotein 2 autoantibodies [Text Words]
No. 9	Autoantibodies (as a MeSH term)
No. 10	OR (Νο. 1 - No. 9)
No. 11	Crohn’s disease
No. 12	Crohn's disease (as a MeSH term)
No. 13	OR (No. 11, No. 12)
No. 14	AND (No. 10, No. 13)
Cochrane-CENTRAL
No. 1	Anti-glycoprotein 2 antibody
No. 2	Autoantibodies to glycoprotein 2
No. 3	Autoantibodies (as a MeSH term)
No. 4	OR (No. 1 - No. 3)
No. 5	Crohn’s disease
No. 6	Crohn's disease (as a MeSH term)
No. 7	OR (No. 5, No. 6)
No. 8	AND (No. 4, No. 7)

No. means order of the keywords entered on PubMed and CENTRAL. OR and AND are Boolean operators used between keywords.

Table 2 Characteristics of the included studies evaluating the diagnostic accuracy of glycoprotein 2 antibodies in Crohn’s disease

Ref.	Country	Multicenter	Recruitment			CD diagnosis and classification		Assays characteristics					Sample characteristics					Funding
			Year	Site	Consecutive	CD diagnosis	Montreal[81]	Assay	Kit	anti-GP2 form	Blind assay	Positivity cut-off U/dL	N9	Unrelated sample	Children included	Sex (% female)	Age (yr)5
Bogdanos et al[41]	Germany; United Kingdom	√	NR	Otto-von-Guericke University; UCL Hospital; and Children’s hospital Technical University Dresden	NR	Standard clinical, radiological, endoscopical and histological criteria[8,9]	√	ELISA	GA (Dahlewitz/Berlin Germany)	Total	No	IgA 20; IgG 20	CD n = 169; UC n = 102; HC n = 225	NR	√	CD 60.3%; UC 55.9%	CD 36 (8-87)1; UC 47 (17-92)1	Higher Education Funding Council of England; Biomedical Research Centre, United Kingdom NIHR; and Brandenburg Ministry of Economics; and EU
Bonaci-Nikolic et al[42]	Serbia	NR	NR	Clinical Center of Serbia	NR	Clinical, endoscopic, histologic, lab findings[21]	-	ELISA	GA (Dahlewitz/Berlin Germany)	Total	No	IgA 20; IgG 24	CD n = 33; UC n = 23; GSE n = 21; HC n = 13	NR	-	CD 42.4%; UC 56.5%; GSE 76.2%; HC 46.1%	CD 35 (19-63)4; UC 34 (24-57)4; GSE 31 (19-57)4; HC 41 (22-55)	None declared
Caneparo et al[43]	Italy	-	2008-2014	Policlinico San Donato	NR	Clinical, endoscopic and histologi-cal criteria	-	ELISA	GA (Dahlewitz/Berlin Germany)	Total	√	IgA 10; IgG 15	CD n=48 UC n=26 HC n=182	NR	√	CD 47.9%; UC 19.2%	CD 41 (16-65)4; UC 39 (17-62)4	Regione Piemonte and Letizia Castelli Schubert Foundation
Cummings et al[44]	United Kingdom	-	2009 -2010	Cleveland Clinic	√	Clinical, endoscopic, radiographic, histopathological criteria[22]	-	ELISA	GA (Dahlewitz/Berlin Germany)	Isoforms GP21 and GP24	√	IgA GP21 14; IgA GP24 3.7; IgG GP21 18; IgG GP24 15	UC n = 117	√	-	UC 44.4%	UC 44.3 ± 13.7	Obtained but not disclosed
Degenhardt et al[45]	Germany	-	2000-2006	University Medical Center Regensburg	NR	European Crohn and Colitis Organization criteria[23]	√	ELISA	GA (Dahlewitz/Berlin Germany)	Isoform alpha and betta	√		CD n =303; UC n =108; OGD n = 72; OPC n = 206	NR	√	CD 52.8%; UC 39.8%; ODG 36.1%	CD 36.1 ± 12.5; UC 40.2 ± 12.8; OGD 60.3 ± 13.8	Bundesministerium für Bildung & Forschung and Kompetenznetz chronisch entzündliche Darmerkrankungen
Gross et al[46]	Netherlands	NR	NR	VU University Medical Center Amsterdam	-	Lennard-Jones criteria[24]	-	ELISA	GA (Dahlewitz/Berlin Germany)	Total	No	IgA 20; IgG 20	CD n = 38; UC n = 40; CeD n = 45; GFD n = 34; RCD n = 15	NR	-	CD 71.1%; UC 52.5%	CD 36.4 ± 11.8; UC 36.5 ± 9.6	CD consortium
Michaels et al[47]	Germany	-	2005-2013	University Hospital Schleswig-Holstein	-	Typical clinical, endoscopical, histological and/or radiological findings of CD/UC	√	IIF	Euroimmun Germany	Total	NR		CD n = 224; UC n = 136	NR	NR	CD 64.3%; UC 54.4%	CD 392; UC 422	Else-Kröner-Fresenius-Stiftung
Op De Beéck et al[48]	Belgium	-	NR	University Hospital Gasthuisberg, Leuven	NR	Lennard-Jones criteria[24]	-	ELISA	GA (Dahlewitz/Berlin Germany)	Total	NR	IgA 15; IgG 15	CD n = 164; UC n = 118; OGD n = 75	NR	√	CD 58.6%6; UC 41.7%6[59]; ODG NR	CD 42 (17-80)16; UC 43 (19-78)1,6[59]; ODG NR	Fund for Scientific Research Flanders and GA GmbH
Papp et al[49]	Hungary	-	2005-2010	Institute of Internal Medicine, University of Debrecen	√	Lennard-Jones criteria[24]	√	ELISA	GA (Dahlewitz/Berlin Germany)	Total	√	IgA 20; IgG 20	CD n = 271; UC n = 187; HC n = 100	NR	-	CD 61.5%; UC 54%	CD 25 (19-33); UC 33 (23-43)	Janos Bolyai Research Scholarship; Debrecen University; and IOIBD Research
Pavlidis et al[50]	United Kingdom	-	NR	UCL Hospital	NR	Lennard-Jones criteria[24]	√	ELISA	GA (Dahlewitz/Berlin Germany)	Total	NR	IgG 20	CD n = 225; UC n = 225	NR	-	CD 56.4%; UC 49.7%	CD 36 ± 14.3; UC 51 ± 15.7	NIHR; Higher Education Funding Council for England; EASL; and INOVA Diagnostics
Pavlidis et al[51]	United Kingdom	-	NR	UCL Hospital	√	Lennard-Jones criteria[24]	√	ELISA	Inova Diagnostics (Research use only)	Total	√	IgA 20; IgG 25	CD n = 323; UC n = 294; OPC n = 112; HC n = 103	NR	-	CD 54%; UC 47.9%	CD 40 ± 14.3; UC 48.7 ± 15.7	INOVA Diagnostics
Pavlidis et al[52]	United Kingdom	-	NR	UCL Hospital	NR	Lennard-Jones criteria[24]	√	IIF	N/A8	Total	NR		CD n = 212; UC n = 249	NR	-	CD 42.4%; UC 51.4%	CD 42.4 (30-49); UC 51.4 (37-61)	Euroimmun
Röber et al[53]	Germany	√	1994-2014	Three children’ s University hospitals (Dresden, Leipzig, Giessen)	NR	Porto criteria[25]	Paris [82]	ELISA	GP21, GP23: (AMS Biotechnology, Abingdon, United Kingdom); GP22: (CCS GmbH, Hamburg, Germany); GP24: (Thermo Sci, Braunschweig, Germany)	Isoforms 1, 2, 3, 4	NR	IgA GP21 7.02; IgA GP22 7.33; IgA GP23 4.37; IgA GP24 9.01; IgG GP21 33.38; IgG GP22 71.75; IgG GP23 15.89; IgG GP24 23.22	CD n = 164; UC n = 114; GE n = 27; ENDO n =56; HC n =218	NR	√	CD 39.6%; UC 54.3%; GE 52%; ENDO 50%	CD 13 (10-15); UC 14 (11-15); GE 2 (1-5); ENDO 13 (7-16)	None declared
Roggenbuck et al[56]	Germany; Greece; Belgium	√	NR	Attikon Hospital, UoA; Otto-von-Guericke University; and University Hospital Leuven	NR	NR. Communication with an author, confirmed the Lennard-Jones criteria[24]	-	ELISA	GA (Dahlewitz/Berlin Germany)	Total	NR		CD n = 73; CeD n = 79; HC n = 90	NR	√7	CD 52%; CeD 69.6%	CD 36.5 (30-43)3; CeD 24 (12-42)3	None declared
Roggenbuck et al[55]	Germany	-	NR	Charité Berlin	NR	Lennard-Jones criteria[24]	-	ELISA	GA (Dahlewitz/Berlin Germany)	Total	NR	IgA 20; IgG 20	CD n = 73; UC n = 49; HC n = 63	NR	-	CD 57.5%; UC 59.1%	CD 41 (20-72)1; UC 40 (21-71)1	Brandenburg Ministry of Economics and EU
Roggenbuck et al[54]	Germany	NR	NR	NR	√	Lennard-Jones criteria[24]	NR	ELISA	GA (Dahlewitz/Berlin Germany)	Total	NR	IgA 20; IgG 20	CD n = 178; UC n = 100; HC n = 162	NR	-	CD 60.7%; UC 54%	CD 39 (18-87)1; UC 42 (18-71)1	Brandenburg Ministry of Economics and EU
Zhang et al[57]	China	-	NR	Peking Union Medical College Hospital	NR	Lennard-Jones criteria[24]	√	ELISA	GA (Dahlewitz/Berlin Germany)	Total	NR	IgA 20; IgG 20	CD n = 35; UC n = 35; OGD n = 13; HC n = 8	NR	√	CD 17%; UC 38%; ODG NR	CD: 17 (13-69)1; UC: 38 (18-75)1; ODG NR	NNSFC
Zhang et al[58]	China	-	NR	Peking Union Medical College Hospital	√	Lennard-Jones criteria[24]	√	ELISA	GA (Dahlewitz/Berlin Germany)	Total	NR	IgA 10; IgG 15	CD n = 171; UC n = 208; BD n = 71; ITB n = 57; HC n = 70	NR	√	CD 33%; UC 43%; BD 38%; ITB 43%	CD 33 (10-85)1; UC 43 (12-77)1; BD 38 (10-73)1; ITB 43 (14-76)1	NNSFC; Chinese Academy of Medical Sciences; and Chinese Key Research & Development Program

¹Median (minimum-maximum).

²median.

³Mean (IQR1-IQR3).

⁴Mean (minimum-maximum).

⁵mean ± standard deviation, or median, IQR.

⁶Not all participants from the Joossens[59] study were included.

⁷Not among participants with Crohn’s disease.

⁸Using as substrates IIF chip slides containing sections of unfixed pancreas, recombinantly transformed HEK293 cells-overexpressing GP2[83].

⁹Healthy controls were not included in the sensitivity and specificity analyses herein. Anti-GP2: Glycoprotein 2 antibodies; BD: Behçet's disease; CD: Crohn’s disease; CeD: Celiac Disease; EASL: European association for the study of liver; ENDO: Nonspecific gastrointestinal symptoms; ELISA: Enzyme-linked immunosorbent assay; EU: European Union; GA: Generic assays; GE: Acute gastroenteritis; GFD: CeD on gluten-free diet; GP2: Glycoprotein 2; GSE: Gluten-sensitive enteropathy; HC: Healthy controls; IBD: Inflammatory bowel diseases; IIF: Indirect immune-fluorescence; ITB: Intestinal tuberculosis; N/A: Not applicable; NIHR: National Institute for Health Research; NNSFC: National Natural Science Foundation of China; NR: Not reported; OGD: Other gastrointestinal disease; OPC: Other pathological conditions; RCD: Refractory Crohn’s disease; UC: Ulcerative Colitis; UCL: University College London; UoA: University of Athens.

Table 3 Investigation of heterogeneity (meta-regression)

Covariate		Population	Ig Type	Number of studies	Relative diagnostic odds ratio (95%CI)
Funding type	State vs Other	CD vs All	IgG	6 vs 9	1.91 (0.87-4.21)
			IgA	5 vs 9	1.08 (0.38-3.06)
		CD vs UC	IgG	5 vs 8	1.21 (0.81-1.80)
COI	Industry-related COI vs no apparent industry-related COI	CD vs All	IgG	7 vs 8	0.73 (0.32-1.66)
			IgA	6 vs 8	0.53 (0.21-1.30)
		CD vs UC	IgG	9 vs 4	0.48 (0.19-1.20)
Method	ELISA vs IFF	CD vs All	IgG	13 vs 2	0.84 (0.38-1.85)
			IgA	12 vs 2	4.25 (1.26-14.37)
		CD vs UC	IgG	11 vs 2	1.60 (0.40-6.54)
Blind assay	No/not stated vs Yes	CD vs All	IgG	12 vs 3	3.28 (1.33-8.09)
			IgA	11 vs 3	1.77 (0.63-5.00)
		CD vs UC	IgG	10 vs 3	1.15 (0.32-4.15)
Consecutive sampling	No/not stated vs Yes	CD vs All	IgG	11 vs 4	1.47 (0.65-3.32)
			IgA	10 vs 4	1.31 (0.53-3.21)
		CD vs UC	IgG	9 vs 4	1.88 (0.65-5.38)
Kit manufacturer	GA vs All other	CD vs All	IgG	12 vs 3	1.04 (0.51-2.11)
			IgA	11 vs 3	1.28 (0.80-2.03)
		CD vs UC	IgG	10 vs 3	1.47 (0.48-4.48)
Female participants	≥ 50% vs < 50%	CD vs All	IgG	11 vs 4	1.24 (0.79-1.94)
			IgA	10 vs 4	0.75 (0.30-1.93)
		CD vs UC	IgG	10 vs 3	1.15 (0.54-2.45)

CD: Crohn’s disease; CI: Confidence interval; COI: Conflict of interest; GA: Generic assays; ELISA: Enzyme-linked immunosorbent assay; IFF: Indirect immune-fluorescence; Ig: Immunoglobulin; UC: Ulcerative Colitis.

Table 4 Summary of finding table based on a hypothetical scenario[38] of applying glycoprotein 2 antibodies tests on a cohort of 10000 patients

Analysis	Diagnostic cut-off (U/dL)	TP	(Range)	FP	(Range)	TN	(Range)	FN	(Range)
CD vs All symptomatic patients (IgG)	Mixed	9	(6-21)	698		9270		23	(21-26)
	20	7	(5-10)	698	(498-897)	9270	(9071-9470)	25	(22-27)
	15	9	(5-14)	797	(399-1,595)	9171	(8373-9569)	23	(18-27)
CD vs UC (IgG)	Mixed	10	(8-12)	698		9270		22	(20-24)
	20	8	(5-11)	698	(399-997)	9270	(8971-9569)	24	(21-27)
	15	9	(5-14)	997	(598-1595)	8971	(8373-9370)	23	(18-27)
CD vs All symptomatic patients (IgA)	Mixed	5	(4-6)	299		9669		27	(26-28)
	20	5	(3-8)	399	(100-1396)	9569	(8572-9868)	27	(24-29)
CD vs UC (IgA)	Mixed	4	(1-6)	199		9769		28	(26-31)
	20	5	(3-7)	199	(100-399)	9769	(9569-9868)	27	(25-27)
CD vs All symptomatic patients (IgA and/or IgG)	Mixed	6	(3-9)	299		9669		26	(20-23)
	20	7	(4-12)	698	(199-1994)	9270	(7974-9769)	25	(20-28)
CD vs UC (IgA and/or IgG)	Mixed	6	(1-11)	299		9669		26	(21-31)

Mixed diagnostic cut-off includes all cut-offs used as well as studies with unreported cut-offs. A prevalence of 322 per 100000 results in 32 patients with Crohn’s disease in this cohort. FN: False negatives; FP: False positives; TN: True negatives; TP: True positives; UC: Ulcerative colitis; Ig: Immunoglobulin.