In patients initially diagnosed with indeterminate colitis, what is the diagnostic accuracy of the DEFA5 bioassay versus standard histological methods (IHC) for differentiating Crohn's colitis from UC

What is known

- In 21 IC patients followed a mean ~8.7 years, DEFA5 IHC counts agreed with the final CC or UC diagnosis in every sample tested. ¹ - A logistic model with CC vs UC as outcome and DEFA5 as the discriminator gave a positive predictive value of 96%, with model R² and ROC AUC reported as 1. ¹ - Even among 6 patients who remained inconclusive by attending gastroenterologist and 3 blinded pathologists, DEFA5 counts (3 high/CC, 3 low/UC) matched the final diagnosis. ¹ - Standard histology left the mean diagnostic delay at about 7 years, and 28.5% of patients could still not be classified into authentic UC or CC. ¹

What is unknown / caveats

- Single retrospective cohort of only 21 IC patients from one center - No formal head-to-head diagnostic-accuracy comparison of DEFA5 versus standard IHC/histology reported - Perfect R² and AUC of 1 come from a fit logistic model, not an independent validation set - The evidence rests on a single small retrospective cohort, so the near-perfect accuracy figures may not generalize.

## References

1. Rana T, Korolkova OY, Rachakonda G, Williams AD, Hawkins AT, James SD, Sakwe AM, Hui N, Wang L, Yu C, Goodwin JS, Izban MG, Offodile RS, Washington MK, Ballard BR, Smoot DT, Shi XZ, Forbes DS, Shanker A, M'Koma AE. Linking bacterial enterotoxins and alpha defensin 5 expansion in the Crohn's colitis: A new insight into the etiopathogenetic and differentiation triggers driving colonic inflammatory bowel disease. PLoS One. 2021;16(3):e0246393. PMID: 33690604.

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