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Testing for IgA anti-tissue transglutaminase in routine clinical practice: Requesting behaviour in relation to
Maurits Damoiseaux1, William van Doorn1, Ellen van Lochem2
1Central Diagnostic Laboratory, Maastricht University Medical Center, Maastricht, the Netherlands.
Insights
Laboratory testing for coeliac disease shows a low positive rate (<2%) for IgA anti-TTG. Guidelines may need refinement to improve the pre-test probability for accurate diagnosis.
Area of Science:
- Clinical immunology
- Gastroenterology
- Laboratory medicine
Background:
- Increased awareness and improved serological tests for coeliac disease have led to a rise in laboratory test requests.
- Understanding requesting patterns across clinical disciplines is crucial for optimizing diagnostic strategies.
Purpose of the Study:
- To evaluate the requesting behavior of different clinical disciplines for coeliac disease serology.
- To analyze the prevalence of positive results in relation to existing guidelines.
- To assess the adherence to diagnostic confirmation protocols.
Main Methods:
- Retrospective analysis of laboratory data over 5 years from tertiary and secondary hospitals.
- Comparison of requesting patterns and positive result rates across clinical disciplines.
Main Results:
- Initial IgA anti-TTG testing yielded a low positive rate (<2%), with slightly higher rates in paediatric patients (2.4-4.0%).
- Confirmation of positive results via IgA anti-endomysium antibodies in an independent sample was infrequent, particularly in paediatric cases.
- Follow-up measurements were common for monitoring gluten-free diet compliance rather than initial diagnosis.
Conclusions:
- The low overall positive rate for IgA anti-TTG suggests a need to refine clinical indications for coeliac disease testing to enhance pre-test probability.
- Emphasis on confirming positive serology in an independent sample is critical, especially for paediatric coeliac disease diagnosis, to potentially avoid biopsy.
Objective:
Due to the high awareness of coeliac disease and improvement of serological tests, the number of requested laboratory tests has increased substantially over the years. In the current study we have evaluated the requesting behaviour of distinct clinical disciplines in relation to the prevalence of positive results and in the context of existing guidelines.
Methods:
Data were retrospectively extracted from the laboratory information system over a time-span of 5 years in a tertiary hospital and compared with the situation in a secondary hospital.
Results:
Data reveal that for initial testing (n=18,183) the percentage positive results for IgA anti-TTG is <2%. Paediatricians have a slightly higher percentage of seropositive results (2.4-4.0%). Early confirmation (<2 months) of positive results by IgA anti-endomysium antibodies in an independent sample is only performed in a minority of paediatric patients. The majority of positive patients, however, have follow-up measurements (<14 months) in order to examine compliance to a gluten-free diet. Interestingly, initial requests for paediatric patients reveal an equal distribution between boys and girls, while in adult patients there is a two times preponderance of requests in female patients, similar to the female/male ratio in patients with positive results, being either paediatric or adult patients.
Conclusion:
Although laboratory testing for coeliac disease may be primarily used to exclude the disease, it is evident that the percentage positive results for IgA anti-TTG is extremely low. This may indicate that the clinical manifestations that warrant testing, should be further specified in order to increase the pre-test probability. As the specific serology is important to bypass a biopsy in the diagnosis of coeliac disease according to the paediatric guideline, the confirmation in an independent sample needs to get more attention.
