Anti-68 kDa antibodies in autoimmune sensorineural hearing loss: are these autoantibodies really a diagnostic tool?

OBJECTIVES: Autoimmune sensorineural hearing loss (ASNHL) is a relatively rare disorder which can lead to total deafness. At present, no specific laboratory test with adequate sensitivity and specificity is available to confirm the clinical suspicion of ASNHL. The aim of this study was to identify if evaluation of anti-hsp70 antibodies is an accurate diagnostic tool in patients affected by ASNHL. STUDY DESIGN: Prospective study. METHODS: During 4-year (2001-2005), all patients with SNHL who were referred to the Eye, Ear, Nose and Throat Department of Parma University, Italy, underwent specific tests to determine the autoimmune origin of the disease. Patients with a consistent suspicion of ASNHL underwent the routine serologic tests and a test for determination of anti-hsp70 antibodies. The same patients were divided into three groups: (1) idiopathic ASNHL; (2) ASNHL associated with ocular inflammation, i.e. Cogan's Syndrome; (3) ASNHL associated with a systemic autoimmune disease (SAD). The control group included: (1) healthy subjects; and (2) patients affected by SAD, without any ocular or audiovestibular disease. RESULTS: 88 subjects (67 patients, defined as "study group", and 21 controls) were evaluated. Anti-hsp70 antibodies were isolated in 52% of the study group patients, and in 4% of the control group (chi2 = 13.009, p < 0.01). In the idiopathic ASNHL patients, 59.5% were found positive for anti-hsp70 antibodies. About 50% of patients affected by CS and 37.5% of patients affected by SAD with SNHL were found positive. In the control group, anti-hsp70 antibodies were found in 8.3% of healthy subjects and in none of the patients with SAD and no hearing loss. CONCLUSIONS: The present study confirms the value of the anti-hsp70 test in the serological diagnosis of autoimmune hearing loss. It is still the only available diagnostic marker that identifies an autoimmune origin of hearing loss.