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

OBJECTIVE: 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.
SETTING: Tertiary hospitals.
METHODS: 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.
RESULTS: 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.
CONCLUSION: 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.