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Purpose: Perilymphatic fistula (PLF), defined as an abnormal communication between the inner and middle ear, presents with a symptomatology of hearing loss and vestibular disorder that is indistinguishable from a number of other inner ear diseases. Methods of diagnosis remain controversial. We previously showed that CTP (Cochlin-tomoprotein) was selectively detected in the perilymph. We also established a definite diagnostic test for PLF using CTP as a biochemical marker. Here, we examined the diagnostic performance of the CTP detection test to determine the usefulness of this test in a clinical setting.
Methods: The CTP detection test was performed using a western blot analysis with recombinant human (rh)CTP as a spiked standard. We evaluated the specificity of the CTP detection test by also testing non-PLF cases. To describe the limitations of the test, we tested samples from patients with middle ear infection. Serially diluted perilymph was tested to determine the detection limit of the CTP test. We then applied the CTP detection test in cases of spontaneous, traumatic and iatrogenic (surgical) PLF.
Findings: We established a standardized CTP detection test using high (0.27 ng) and low (0.13 ng) spiked standards of rhCTP and a western blot analysis. MEL (middle ear lavage) samples from 54 of the 55 non-PLF cases tested negative for CTP, i.e., the specificity of the test was 98.2%. MEL samples from 43 out of 46 cases with chronic suppurative otitis media or middle ear cholesteatoma tested negative for CTP. The detection limit in perilymph was 0.161 uL/lane for an average of 5 samples. We elucidated the clinical characteristics of the PLF cases in each category.
Interpretation: CTP is a stable perilymph specific protein, and this CTP detection may be the first clinically established diagnostic tool for the detection of PLF with a high specificity. PLF is surgically correctable by sealing the fistula. The appropriate recognition and treatment of PLF can improve hearing and balance in afflicted patients.