28 - Patterns in Follow-Up Testing for Individuals Newly Positive for Celiac Disease Antibodies

Tuesday, October 24, 2023

8:30 AM – 8:40 AM PT

Location: Ballroom B

Presenting Author(s)

James King, MSc(Epi)

University of Calgary
Calgary, AB, Canada

PDF of Slides View Slides

James King, MSc(Epi), Jessalyn K. Holodinsky, PhD, Amy Metcalfe, PhD, Darren Brenner, PhD, Gilaad G. Kaplan, MD, MPH, Tyler Williamson, PhD
University of Calgary, Calgary, AB, Canada

Introduction: Rates of diagnosed celiac disease have increased over the last 25 years. Following diagnosis, North American guidelines recommend monitoring disease status through regular tissue transglutaminase antibodies (TTG) testing. However, adoption of these guidelines in a real-world, population-based setting has not been investigated.

Methods: Health administrative data in Alberta Canada were used to identify incident cases and subsequent follow-up testing between 2016 and 2020. Repeated time-to-event analyses employing Prentice, Williams and Peterson gap-time models were performed to estimate differences in follow-up testing by sex, age, geographic region, material deprivation, baseline TTG, and severity of comorbidities. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated overall and by event-specific tests (e.g., index to first test follow-up test, first follow-up to second).

Results: A total of 1,744 children and 5,114 adults were included, with a follow-up time of 3,871 and 12,463 person-years, respectively. Within five years of index tTG-IgA positivity, 76% of children had at least one follow-up tTG-IgA test compared to 56% of adults (Figure 1A). Those living in metropolitan areas had higher probability of subsequent testing in both children (HR=1.38, 95% CI:1.23-1.54) and adults (HR=1.43, 95% CI:1.31-1.56) (Table 1). Children from the least deprived areas showed slightly higher hazards of repeated testing compared to those most deprived (HR=1.18, 95% CI:1.03-1.36) (Table 1). In adults, females had a marginally higher probability of follow-up testing (HR=1.11, 95% CI:1.04-1.19) (Table 1). Index tTG-IgA results were associated with repeated testing, but in opposite directions for children and adults (Table 1). On average, children received 2.2 follow-up tests compared to 1.3 among adults within five years of index positivity (Figure 1B). Event-specific associations between patient subgroups became nullified beyond the first follow-up test.

Discussion: Approximately 1 in 4 children and 1 in 2 adults did not receive a follow-up TTG test within five years of initial positivity. While there were notable differences in subsequent testing by geographic location and socioeconomic deprivation, these disparities may not persist after the first follow-up TTG test. Quality assurance studies are necessary to explain poor adherence to guidelines of surveillance of TTG.

Figure: Figure 1A: Time from index TTG positivity to first follow-up test
Figure 1B: Estimated mean cumulative functions for repeated tTG-IgA tests

Category	Comparison	HR (95% CI)	p-value
Children
Sex	Female vs. male	0.96 (0.88, 1.05)	0.325
Age	Continuous	0.98 (0.96, 0.99)	< 0.001
Metropolitan	Metropolitan vs. non-metropolitan	1.38 (1.23, 1.54)	< 0.001
Material deprivation	(1) Least deprived vs. (5) most deprived	1.18 (1.03, 1.36)	0.021
	(2) vs. (5) most deprived	1.19 (1.03, 1.37)	0.016
	(3) vs. (5) most deprived	1.07 (0.93, 1.23)	0.318
	(4) vs. (5) most deprived	1.01 (0.87, 1.16)	0.939
Index result*	Continuous	1.05 (1.05, 1.06)	< 0.001
Comorbidity¹	Non-complex chronic vs. non-chronic	1.05 (0.98, 1.21)	0.119
Comorbidity¹	Complex chronic vs. non-chronic	1.10 (0.93, 1.29)	0.267
Adults
Sex	Female vs. male	1.11 (1.04, 1.19)	0.002
Age	Continuous	1.00 (1.00, 1.00)	0.107
Metropolitan	Metropolitan vs. non-metropolitan	1.43 (1.31, 1.56)	< 0.001
Material deprivation	(1) Least deprived vs. (5) most deprived	1.10 (0.99, 1.22)	0.072
	(2) vs. (5) most deprived	0.98 (0.88, 1.09)	0.736
	(3) vs. (5) most deprived	1.09 (0.98, 1.21)	0.125
	(4) vs. (5) most deprived	1.09 (0.98, 1.21)	0.127
Index result*	Continuous	0.99 (0.98, 0.99)	< 0.001
Comorbidity²	Charlson index: 1 vs. 0 (no comorbidities)	0.98 (0.91, 1.06)	0.678
	Charlson index: 2 vs. 0	1.02 (0.91, 1.15)	0.751
	Charlson index: ≥3 vs. 0	1.00 (0.88, 1.13)	0.987

*based on tTG-IgA value times the upper limit of normal ¹Pediatric Medical Complexity Algorithm (Simon et al. Pediatrics. 2014) ²Charlson comorbidity index (Quan et al. Med Care. 2005)

Table: Table 1: Overall repeated events analyses, by age category

Disclosures:

James King indicated no relevant financial relationships.

Jessalyn Holodinsky indicated no relevant financial relationships.

Amy Metcalfe indicated no relevant financial relationships.

Darren Brenner indicated no relevant financial relationships.

Gilaad Kaplan: AbbVie (received honoraria) – Consultant, Speaking. Amgen (received honoraria) – Consultant, Speaking. Ferring – Grants for research support. Janssen (received honoraria) – Consultant, Speaking. Pendophram (received honoraria) – Consultant, Speaking. Pfizer (received honoraria) – Consultant, Speaking. Sandoz (received honoraria) – Consultant, Speaking. Takeda (received honoraria) – Consultant, Speaking. TREATMENT OF INFLAMMATORY DISORDERS, AUTOIMMUNE DISEASE, AND PBC. UTI Limited Partnership, assignee. Patent WO2019046959A1. PCT/CA2018/051098. 7 Sept. – Intellectual Property/Patents.

Tyler Williamson indicated no relevant financial relationships.

James King, MSc(Epi), Jessalyn K. Holodinsky, PhD, Amy Metcalfe, PhD, Darren Brenner, PhD, Gilaad G. Kaplan, MD, MPH, Tyler Williamson, PhD, 28, Patterns in Follow-Up Testing for Individuals Newly Positive for Celiac Disease Antibodies, ACG 2023 Annual Scientific Meeting Abstracts. Vancouver, BC, Canada: American College of Gastroenterology.