Diagnostic Yield of Next-generation Sequencing in Very Early-onset Inflammatory Bowel Diseases: A Multicentre Study

BACKGROUND AND AIMS

An expanding number of monogenic defects have been identified as causative of severe forms of very early-onset inflammatory bowel diseases [VEO-IBD]. The present study aimed at defining how next-generation sequencing [NGS] methods can be used to improve identification of known molecular diagnosis and to adapt treatment.

METHODS

A total of 207 children were recruited in 45 paediatric centres through an international collaborative network [ESPGHAN GENIUS working group] with a clinical presentation of severe VEO-IBD [n = 185] or an anamnesis suggestive of a monogenic disorder [n = 22]. Patients were divided at inclusion into three phenotypic subsets: predominantly small bowel inflammation, colitis with perianal lesions, and colitis only. Methods to obtain molecular diagnosis included functional tests followed by specific Sanger sequencing, custom-made targeted NGS, and in selected cases whole exome sequencing [WES] of parents-child trios. Genetic findings were validated clinically and/or functionally.

RESULTS

Molecular diagnosis was achieved in 66/207 children [32%]: 61% with small bowel inflammation, 39% with colitis and perianal lesions, and 18% with colitis only. Targeted NGS pinpointed gene mutations causative of atypical presentations, and identified large exonic copy number variations previously missed by WES.

CONCLUSIONS

Our results lead us to propose an optimised diagnostic strategy to identify known monogenic causes of severe IBD.

Interferon-gamma assays for the diagnosis of tuberculosis infection before using tumour necrosis factor-alpha blockers

OBJECTIVES

Patients who receive tumour necrosis factor-alpha (TNF-alpha) blockers are mostly immunosuppressed. A study was performed to investigate whether an interferon-gamma (IFN-gamma) assay could represent an alternative approach to the tuberculin skin test (TST) for the diagnosis of latent tuberculosis infection (LTBI) in these patients.

DESIGN

We prospectively enrolled 106 individuals into the study in two groups. Group 1 consisted of 38 healthy individuals and Group 2 included 68 patients with chronic inflammatory diseases evaluated for LTBI before the use of TNF-alpha blockers.

RESULTS

Of all participants, nine had indeterminate IFN-gamma test results. Agreement between the two tests was poor in both groups (kappa values respectively -0.54 and 0.18). In a total of 97 subjects, 10 (10.3%) were positive by the IFN-gamma test and 49 (50.5%) by TST.

CONCLUSION

We found poor agreement between TST and the IFN-gamma test in our study. Our limited preliminary data should be accepted as a basis for designing future studies that will be helpful for physicians to decide whether the IFN-gamma test is more sensitive than the TST test in detecting LTBI before the use of TNF-alpha blockers.