Distortion-product otoacoustic emission: early detection in deferoxamine induced ototoxicity.
OBJECTIVE
Deferoxamine therapy in lifelong transfusion-dependent anaemias, as beta-thalassemia major, is associated with an increased risk of ototoxic changes. With increasing survival rates, prevention and/or early detection of ototoxicity are important for providing management options. The predictive value of pure-tone audiometry in early detection of ototoxicity has been questioned, particularly in the higher frequencies. Otoacoustic emissions appear to be more sensitive to cochlear insult than the conventional pure-tone audiometry. The aim of our study was to compare the efficacy of otoacoustic emissions (distortion-product otoacoustic emissions) with that of pure-tone audiometry as method of audiological monitoring.


METHODS
Baseline audiometric (0.25-8kHz) and otoacoustic emission testing (distortion-product otoacoustic emissions) was conducted in a group of patients with beta-thalassemia major, 60 of whom met the criteria for inclusion in the study. Comparisons were performed between baseline measurements and those recorded after 20 months. Distortion-product otoacoustic emissions were obtained as DP-grams. The DP-gram amplitude was determined for each child.


RESULTS
Threshold changes from baseline were found to be statistically significant from 4 to 8kHz in 68.4% of the subjects (P<0.01). Distortion-product otoacoustic emissions demonstrated a significant threshold shift and a decreased amplitude in the frequencies >3kHz (P<0.05). Furthermore, DP-gram amplitude also reduced significantly at 3kHz (P<0.05) without any similar change in pure-tone audiometry.


CONCLUSIONS
As ototoxicity screening tool DP-gram was extremely sensitive and superior to pure-tone audiometry. Their use is recommended for regular monitoring of cochlear function, aiming in prevention of permanent damage.
Delehaye
Emilio
E
University Department of Otolaryngology Head and Neck Surgery, viale San Pietro 43, 07100 Sassari, Italy. delemy@tiscali.it
Capobianco
Saverio
S
Bertetto
Ivano Bruno
IB
Meloni
Francesco
F
D000293:Adolescent; D000328:Adult; D020237:Alexia, Pure; D002648:Child; D003676:Deferoxamine / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous / Q000187:drug effects*; D017086:beta-Thalassemia / Q000188:drug therapy
D003676:Deferoxamine