Clinical utility of quantitative multi-antibody Polycheck immunoassays in the diagnosis of coeliac disease

Table 1 Characteristics of the patients

	Coeliac disease	Non-coeliac disease
No. of patients	50	50
Females	28 (56%)	29 (58%)
Males	22 (44%)	21 (42%)
Mean age in years	8.7 ± 4.7 (2.5-17.5)2	11.6 ± 4.8 (3-17.5)
Histopathological results1
Marsh 0	0	50 (100%)
Marsh II	6 (12%)	0
Marsh III (a-c)	44 (88%)	0

¹Biopsy results were classified according to the Marsh-Oberhüber classification[11];

²In the coeliac disease patients study group were 3 children ≥ 2 years old.

Table 2 Statistical sensitivity and specificity of Polycheck Celiac IgA and IgG tests for single antibody and for selected multi-antibody combinations

Specific coeliac antibody	Sensitivity %	Specificity %	PPV %	NPV %	AU ROC	LR+2	LR-
Single antibody positivity
Anti-tTG-IgA1	97.7%	100.0%	100.0%	98.0%	98.9%	-	0.023
Anti-tTG-IgG	48.0%	98.0%	96.0%	65.3%	73.0%	24.000	0.531
Anti-DPG-IgA1	34.1%	98.0%	93.8%	62.8%	68.1%	17.045	0.673
Anti-DPG-IgG	100.0%	96.0%	96.2%	100.0%	98.0%	25.000	0.000
Combination of two or more positive antibodies
Anti-tTG-IgA/-IgG + anti-DGP-IgG/-IgA	98.0%	100.0%	100.0%	98.0%	99.0%	-	0.020

¹Calculations after excluding patients with selective IgA deficiency;

²For strategies, where specificity of a test/combination was 100%, the likehood ratio for a positive result could not be calculated. PPV: Positive predictive value; NPV: Negative predictive value; AU ROC: Area under a receiving operator characteristic curve; LR+: Likehood ratio for a positive result; LR-: Likehood ratio for a negative result.

Table 3 Antibody profile in celiac disease patients and non-celiac disease controls

Anti-tTG-IgA	Anti-tTG-IgG	Anti-DGP-IgA	Anti-DGP-IgG	CD patientsn = 50	Non-CD controlsn = 50	Totaln = 100	Classification in combination (anti-tTG-IgA/IgG + anti-DGP-IgG/IgA)
+	+	+	+	7 (14%)	0	7	49 positives
+	+	-	+	11 (22%)	0	11
+	-	+	+	8 (16%)	0	8
+	-	-	+	17 (34%)	0	17
-	+	-	+	61 (12%)	0	6
-	-	-	+	1 (2%)	2 (4%)	3	5 not classified
-	-	+	-	0	1 (2%)	1
-	+	-	-	0	1 (2%)	1
-	-	-	-	0	46 (92%)	46	46 negatives

¹Patients with confirmed selective IgA deficiency. +: Antibody present; -: Antibody absent; Using the combination of four antibodies (anti-tTG-IgA/IgG + anti-DGP-IgG/IgA) classified 49 children as CD positive, 46 as CD negative, and 5 were neither classified as CD positive nor negative with further verification needed. CD: Celiac disease; DGP: Deamidated gliadin peptides; tTG: Tissue transglutaminase.