The clinical value of immittance testing in the identification of middle ear pathology in South African mineworkers

Abstract

This study was conducted to determine the clinical value of immittance testing in the identification of middle ear pathology among South African mineworkers. Case histories, pure tone audiometric screening, otoscopy, tympanometry and acoustic reflex testing were administered to 177 workers at Harmony gold mine in Randfontein, South Africa, within the context of the mine’s programme of medical surveillance for noise exposure. Middle ear pathology was identified on the basis of a proposed middle ear screening protocol, which included medical history-taking, otoscopic examination, pure tone audiometry and immittance testing. A high prevalence of abnormal middle ear results was identified by immittance testing in the population of mineworkers. More than half of the population was positively identified with potential middle ear pathology. The present study found that mineworkers who smoke or are subjected to second-hand smoke have higher incidence of abnormal outer and middle ear results. Otoscopic findings indicated that retracted tympanic membranes were the most common type of middle ear pathology among those identified, followed by scar tissue the tympanic membrane or an inflamed tympanic membrane, and dull tympanic membranes, all of which correlated with the findings of immittance testing. A review of medical history should include information on any pathology indicating previous barotrauma. Screening for hearing disorders forms an essential part of medical surveillance in the deep mining industry. Mine medical staff was often found to be unfamiliar with middle ear barotrauma, which may influence decisions on referral and further assessment of barotrauma-susceptible individuals. The risk of barotrauma during vertical conveyance increases greatly where middle ear pathology is present, but it was found that mineworkers are not excluded from underground work where middle ear pathology is present, thereby exposing them to the risk of barotrauma. Mineworkers should be counseled regarding the consequences of middle ear pathology, and be encouraged to report problems, e.g. pain, suspected ear infection or tympanic membrane perforation, which they presently fail to do. A greater prevalence of middle ear pathology was identified among subjects screened with the proposed immittance testing protocol than was found by conventional screening methods. The existing and proposed screening protocols used during the study are detailed and discussed, to evaluate findings and identify possible reasons for the differing prevalence of middle ear pathology determined by the two different screening methods.