An Evaluation of Sensory Neural Hearing Loss in Thalassaemic Patients Treated with Desferrioxamine and Its Risk Factors
Abstract
Back ground: In major thalassaemia patients who need blood transfusion, iron overload is a major therapeutic disadvantage that leads to heart failure which is the major cause of death in such patients. Desferrioxamine (DFO) is the most efficient factor for iron chelation, but it carries adverse effects such sensory-neural hearing loss.
Methods: The study began in March 2002 and continued untill March 2003, on 160 cases of thalassaemia to determine the incidence of sensory – neural hearing loss and its risk factors in patients who received Desferrioxamine (DFO). All cases underwent audiometric tests. Retrospectively, other needed information were either obtained through interview or extracted from the medical files. Results were analyzed with ANOVA, t-test and Chi-square tests.
Results: Seventy-six patients of the total 156 patients showed impairment in PTA (48.7%) with 24 of them suffering significant involvement (15.4%). These abnormalities generally affected high frequencies including, 4000 and 8000 Hz. Male gender, increased serum billirubin level and fasting blood sugar were statistically correlated with hearing loss (p.v = 0.038, p.v = 0.38, p.v = 0.002 respectively). There was no significant correlation between hearing loss and other factors. Mean DFO administration in patients, was 29.69 mg/kg/day and mean therapeutic index of DFO was 0.01 mg/kg/day/mg/lit. Both of them were below the critical level (<40mg/kg/day and <0.025mg/kg/day/mg/lit respectively), however hearing loss had developed.
Conclusion: Controlling DFO dosage per se does not seem to be enough for decreasing ototoxicity rate. Periodic audiometric tests are highly recommended to detect hearing loss as soon as possible. There are some other factors such as male gender, increased billirubin and FBS, which contribute to DFO ototoxicity. Looking for these risk factors and controlling them, would help identifying susceptible patients and preventing this complication.
Key words: Desferrioxamine (DFO), Sensory-neural hearing loss (SNHL), Thalassaemia therapeutic index (TI)
Methods: The study began in March 2002 and continued untill March 2003, on 160 cases of thalassaemia to determine the incidence of sensory – neural hearing loss and its risk factors in patients who received Desferrioxamine (DFO). All cases underwent audiometric tests. Retrospectively, other needed information were either obtained through interview or extracted from the medical files. Results were analyzed with ANOVA, t-test and Chi-square tests.
Results: Seventy-six patients of the total 156 patients showed impairment in PTA (48.7%) with 24 of them suffering significant involvement (15.4%). These abnormalities generally affected high frequencies including, 4000 and 8000 Hz. Male gender, increased serum billirubin level and fasting blood sugar were statistically correlated with hearing loss (p.v = 0.038, p.v = 0.38, p.v = 0.002 respectively). There was no significant correlation between hearing loss and other factors. Mean DFO administration in patients, was 29.69 mg/kg/day and mean therapeutic index of DFO was 0.01 mg/kg/day/mg/lit. Both of them were below the critical level (<40mg/kg/day and <0.025mg/kg/day/mg/lit respectively), however hearing loss had developed.
Conclusion: Controlling DFO dosage per se does not seem to be enough for decreasing ototoxicity rate. Periodic audiometric tests are highly recommended to detect hearing loss as soon as possible. There are some other factors such as male gender, increased billirubin and FBS, which contribute to DFO ototoxicity. Looking for these risk factors and controlling them, would help identifying susceptible patients and preventing this complication.
Key words: Desferrioxamine (DFO), Sensory-neural hearing loss (SNHL), Thalassaemia therapeutic index (TI)