Objective: To test whether detection of serum antibody to a 68-kd inner ear protein distinguishes among different causes of sensorineural hearing loss, and identifies patients with active disease and those likely to respond to corticosteroid therapy.
Design: Serum samples were tested by Western blot using bovine inner ear extract as antigen, and results were correlated with patient information obtained by chart review.
Setting: Referral center.
Subjects of study: Serum samples were obtained from patients with idiopathic, progressive, bilateral sensorineural hearing loss (IPBSNHL) (n = 72) otosclerosis (n = 11), Cogan's syndrome (n = 8), patients with positive tests for antinuclear antibodies (n = 10), and normal controls (n = 53).
Main outcome measure: Detection of serum antibody to a 68-kd inner ear protein.
Results: Serum from 42 to 72 patients with IPBSNHL reacted with a 68-kd protein constituent of inner ear extract. This reactivity was not detected in serum from 11 of 11 patients with otosclerosis, or in eight of eight with Cogan's syndrome. It was found in serum from one of 10 patients with a positive test for antinuclear antibody and in one of 53 normal controls. Antibody to the 68-kd protein was detected in serum from 89% of patients with actively progressing IPBSNHL and none of the 25 patients with inactive disease (P < .001). Patients who were antibody-positive responded to steroid treatment more frequently than did those who were antibody-negative (P < .001).
Conclusions: These results indicate that the presence of circulating antibody to a 68-kd constituent of bovine inner ear extract serves as a marker for IPBSNHL and that its presence correlates with disease activity and responsiveness to corticosteroid treatment.