Question
A baseline audiogram was done in 1994. The patient had no STS (standard threshold shift) until this year, 2004. When do you change the baseline audio to the new audiogram?
Answer
According to the Occupational Safety & Health Administration (OSHA), if a standard threshold shift (STS) -- defined as an average of 10 dBA or more at 2000, 3000, and 4000 Hz -- occurs in either ear, the employer must follow certain procedures (outlined in the Occupational Noise Standard, 29 CFR 1910.95) including notifying the affected employee in writing. Hearing loss cases that meet specific criteria must be recorded on the OSHA 300 log according to the recordkeeping requirements of Standard 29 CFR 1904.10.
OSHA allows employers to revise the baseline by substituting the annual audiogram for the baseline audiogram when the reviewing professional (audiologist or physician) determines that an STS is persistent. Such a revision would serve to prevent the same STS from being identified repeatedly for an employee whose hearing has stabilized. As a corollary, an annual audiogram may be substituted for the baseline audiogram when thresholds have significantly improved.
When the professional evaluating the audiogram determines that a baseline revision is appropriate, whether due to a persistent STS or improved thresholds, the baseline must be revised for each ear separately. For example, although an employee's annual audiogram shows hearing thresholds deteriorating in both ears simultaneously, occasionally an audiogram will show that an employee is suffering an STS in only one ear. This can sometimes be attributed to working near a loud noise source that is close to the affected ear. If such a shift is shown to be persistent in the judgment of the professional evaluating the audiogram, then the baseline audiogram may be revised due to the persistent STS. A baseline audiogram that shows a persistent shift for only one ear may be revised for only that ear. The baseline may not be revised for the other unaffected ear. This procedure is required because it provides a clear indication of how each ear is affected by noise.
If you have additional questions, call the OSHA Office of Health Enforcement at (202) 693-2190.
References
Occupational Safety & Health Administration, U.S. Department of Labor. Standard Interpretations: Baseline audiogram revision due to persistent STS or improved thresholds; revision must be made for each ear separately. May 8, 2003.
www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=24565
National Hearing Conservation Association. Position Statement: Guidelines for Audiometric Baseline Revision. February 24, 1996.
www.hearingconservation.org/nhca/pos_audiometric.html
Robert Folmer earned B.A. and M.A. degrees in biology from San Francisco State University. He received his Ph.D. in Speech and Hearing Science from the University of California, San Francisco. In 1997 he joined the staff of the Oregon Health & Science University Tinnitus Clinic where he currently serves as Clinical Neurophysiologist and Assistant Professor of Otolaryngology. In addition to his duties evaluating and treating patients in the Tinnitus Clinic, Dr. Folmer also develops and presents hearing conservation curricula for school-age children.