Learning Objectives: In order to better understand the inner ear damage in chronic inflammatory ears, the diagnosis and treatment of cholesteatoma induced fistulae is very important. Here in this talk, new staging method of fistulae using a biomarker is introduced and discussed with the previous methods.

Introduction: Previously proposed staging methods of labyrinthine fistulae include; A) the depth or severity of labyrinthine structure involvement (Dornhoffer et al. Palva et al.) B) Diameter of the fistula (Gacek). In this presentation I will introduce a novel method of staging using a biochemical marker.

Methods: CTP (Cochlin tomo-protein, an isoform of Cochlin), perilymph specific protein, is a novel and unique biomarker. We reported a biochemical test for perilymph leakage detecting CTP in middle ear lavage (MEL, lavaging the middle ear cavity using 0.3 ml saline). Recently we could establish a highly reliable ELISA-kit to detect CTP. The Japanese PLF diagnosis criterion is now based on the visual identification of the fistula (not a leakage) and/or detecting CTP. With a help of private clinical test enterprise (SRL inc.) in Japan, CTP test is widely available nationwide, in 170 hospitals.

If there is 2ul of leaked perilymph in the MEL, the test is positive. The diagnostic performance of the test has a high reliability, and the AUC in ROC analysis was greater than 0.90.

Results: We have tested fistulae and suspected fistulae induced by cholesteatoma. If the diameter of the fistula is more than 2 mm, there is more chance to detect CTP.

Conclusions: CTP test is a objective biochemical test to detect PL leakage. The visual judgment of “the depth or severity” of the fistula propped previously is a subjective judgment. The detection of CTP correlated better with the diameter of the fistulae.