title: Overall versus individual changes for otoacoustic emissions and audiometry in a noise-exposed cohort.
abstract: OBJECTIVE
  For a noise-exposed group of workers, group-averaged and individual changes were compared for pure-tone audiometry, transient-evoked otoacoustic emissions (TEOAEs), and distortion product otoacoustic emissions (DPOAEs) in order to see if they exhibit the same pattern in time.
  
  
  METHODS
  Baseline and 17-months follow-up hearing status was examined with pure-tone audiometry, TEOAEs, and DPOAEs.
  
  
  METHODS
  A total of 233 noise-exposed employees were measured, while 60 subjects from this group contributed to test-retest reliability measures.
  
  
  RESULTS
  Group-averaged changes and individual shifts followed similar patterns: decreases for audiometry at 6-8 kHz and DPOAE at 1.5 kHz, and enhancements for DPOAE at 3 kHz. TEOAEs showed an overall deterioration while both individual deteriorations and enhancements were larger than chance. DPOAE at 6 kHz showed the largest group-averaged change, while the number of individual shifts was not significant. There were no clear relations between changes in audiometry and changes in OAE.
  
  
  CONCLUSIONS
  Significant individual OAE changes do not necessarily follow the same pattern as the group-averaged results. This limits the applicability of OAE testing for the monitoring of individual subjects. Furthermore, hearing deterioration might manifest itself in a local enhancement of otoacoustic emissions and not only in the form of decreases in amplitude.
authors.affiliation: Clinical and Experimental Audiology, ENT Department, Academic Medical Centre, Amsterdam, The Netherlands. h.w.helleman@amc.nl
authors.forename: Hiske W
authors.initials: HW
authors.lastname: Helleman
authors.forename: Wouter A
authors.initials: WA
authors.lastname: Dreschler
mesh_terms: D000328:Adult; D001299:Audiometry / Q000592:standards*; D006317:Hearing Loss, Noise-Induced / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure; D055815:Young Adult