Probabilities of ossicular discontinuity in chronic suppurative otitis media using pure-tone audiometry

To analyze the likelihood ratios (LRs) and predictive values of preoperative air-bone gap (ABG) levels on the presence of gross ossicular discontinuity (OD) among chronic suppurative otitis media (CSOM) patients.

Tertiary hospitals.

Records of 276 patients with CSOM 7 to 75 years old undergoing their first tympanomastoidectomy were reviewed. Association of preoperative audiogram on the presence of OD was analyzed using logistic regression analysis and chi 2 tests. Frequency-specific ABG values were compared with the presence of OD.

In CSOM without cholesteatoma, the ABG of 20 dB or less at 500 Hz (LR [-], 0.119; 95% confidence interval [CI], 0.016-0.867) and 30 dB or less at 1 kHz (LR [-], 0.276; 95% CI, 0.087-0.876) decreased probability of OD from 33 to 5.6% and 15.5%, respectively. Air-bone gap levels of greater than 30 dB at 2 kHz (LR [+], 2.8; 95% CI, 1.4-5.9) and greater than 40 dB at 4 kHz (LR [+], 2.2; 95% CI, 1.2-3.9) increased the probability of OD from 33 to 51 to 89%. In the presence of cholesteatoma, the chance of OD was 88%. The ability of ABG to alter probability of OD was not significant in the presence of cholesteatoma.

Narrow ABG at lower frequencies suggested absence of OD. Wide ABG at higher frequencies suggested presence of OD. Simple tympanoplasty can be done to patients with a small chance of OD as assessed by pure-tone audiometry, whereas a mandatory exploration of the ossicular chain with possible reconstruction was suggested on subjects with a high chance of OD. The presence of cholesteatoma warrants ossicular chain exploration.