The diagnostic performance of a novel ELISA for human CTP (Cochlin-tomoprotein) to detect perilymph leakage

Abstract

Perilymphatic fistula is defined as an abnormal communication between the perilymph-filled space and the middle ear, or cranial spaces. The manifestations include a broad spectrum of neuro-otological symptoms such as hearing loss, vertigo/dizziness, disequilibrium, aural fullness, tinnitus, and cognitive dysfunction. By sealing the fistula, perilymphatic fistula is a surgically correctable disease. Also, appropriate recognition and treatment of perilymphatic fistula can improve a patient’s condition and hence the quality of life. However, the difficulty in making a definitive diagnosis due to the lack of an appropriate biomarker to detect perilymph leakage has caused a long-standing debate regarding its management. We have reported a clinical test for the diagnosis of perilymphatic fistula by detecting a perilymph specific protein, Cochlin-tomoprotein, as a diagnostic marker using a western blot. The aim of this study is to establish an ELISA-based human Cochlin-tomoprotein detection test and to evaluate its diagnostic accuracy in clinical subjects. The results of ELISA showed good dilution reproducibility. The mean concentration was 49.7±9.4 of 10 perilymph samples. The ROC curve in differentiating the perilymph leakage condition from the normal middle ear was significant (P < 0.001) with an area under the curve (AUC) of 0.918 (95% CI 0.824–0.100). We defined the diagnostic criteria as follows: CTP<0.4 negative; 0.4≦CTP<0.8 intermediate; 0.8≦CTP(ng/ml) positive in the clinical usage of the hCTP ELISA, and sensitivity and specificity were 86.4% and 100%, respectively. We further tested the expression specificity of the Cochlin-tomoprotein by testing blood and CSF samples. The concentration was below the detection limit (0.2 ng/ml) in 38 of the 40 blood, and 14 of the 19 CSF samples. We report the accuracy of this test for the diagnosis of perilymphatic fistula. Using ELISA, we can improve the throughput of the test. Furthermore, it is useful for a large-scale study to characterize the clinical picture and delineate the management of this medical condition.

Perilymphatic Fistula: A Review of Classification, Etiology, Diagnosis, and Treatment

“…Beta-2 transferrin and cochlin tomoprotein (CTP) have been targets of research as a potential way to confirm the leakage of perilymph within the middle ear. This test shows great promise and is continuously available as an investigator-initiated trial throughout Japan since first introduced by Ikezono et al in 2009 ( 40 ). Recently in June 2020, the Japan Ministry of Health, Labor, and Welfare approved the CPT ELISA test which has qualities for medical diagnosis (personal communication).…”

“…Unlike beta-2 transferrin, CTP is a protein found in perilymph but not in appreciable amounts in CSF ( 45 ). Western blot and ELISA testing of fluid and lavages from the middle ear for CTP shows promise as a reliable diagnostic tool for PLFs ( 23 , 40 , 46 , 47 ). Currently, the test is limited by the presence of CTP in blood, which may represent a route for sample contamination; however, lavage techniques and centrifugation should dilute or remove any blood in the sample enough so as not to affect the final result of the CTP analysis ( 40 ).…”

Congenital Membranous Stapes Footplate Producing Episodic Pressure-Induced Perilymphatic Fistula Symptoms

“…We have developed an ELISA for human CTP and defined the cutoff criteria as CTP ≧ 0.8 positive, 0.8 > CTP ≧ 0.4 intermediate, and 0.4 > CTP negative (ng/ml). The sensitivity and the specificity of the test to detect perilymph leakage was 86.4 and 100%, respectively (5). The detection of CTP in the middle ear indicates the presence of a fistula and perilymph leakage.…”

“…The vestibular symptoms and nystagmus disappeared immediately after the operation, and at her 1-month follow-up assessment, her hearing improved (Figure 4). Postoperatively, a CTP detection test revealed a concentration of 0.84 ng/ml, which is positive, with the cutoff criteria being CTP ≧ 0.8 positive, 0.8 > CTP > 0.4 intermediate, and 0.4 > CTP negative (ng/ml) (5).…”

“…Using this novel test, the Japanese diagnostic criteria were established ( Table 1). This test is continuously available as an investigator-initiated trial throughout Japan by Ikezono et al (5) and funded by Saitama Medical University. In June 2020, the Japanese Ministry of Health Labor Standards approved the CTP ELISA Test, which has qualities for medical diagnosis.…”