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Spectral gradient acoustic reflectometry only an adjunct for specific otoscopic diagnoses
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Pneumatic otoscopy is a superior tool for diagnosis, but spectral gradient acoustic reflectometry can be a useful adjunct, according to results of a recently published study.
Miia K. Laine, MD, of the department of pediatrics at Turku University Hospital in Finland, and colleagues examined 514 children aged 6 to 35 months in a primary care setting to determine whether spectral gradient acoustic reflectometry (SG-AR) could be used to hone in on specific otoscopic diagnoses. The researchers compared SG-AR with pneumatic otoscopy alone and evaluated the proportions of five manufacturer-recommended SG-AR levels compared with specific otoscopic diagnoses in 2,802 symptomatic examinations and 1,240 asymptomatic clinician visits.
Laine and colleagues said for symptomatic visits, when the angle value was more than 95° (Level 1), 76% of otoscopic diagnoses were healthy middle ear and 5% were acute otitis media. Angle values between 70° and 95° (Level 2), and angle values between 60° and 69° (Level 3) were unrelated to any otoscopic diagnosis. However, Level 4 was related to AOM in 50% of examinations and in otitis media with effusion (OME) in 33%; Level 5 was associated with AOM in 64% and OME in 32% of examinations.
The researchers concluded that SG-AR use alone was not an effective means of making specific otoscopic diagnoses. Although SG-AR’s levels can differentiate between effusion and no effusion, similar to tympanometry, it cannot differentiate between AOM and OME.
Disclosure: Dr. Laine reports no relevant financial disclosures.
Perspective
Back to TopMichael E. Pichichero, MD
We use acoustic reflectometry in our practice often. Because you do not need to achieve a seal of the tip inside the external auditory canal as is necessary for tympanometry, we find it much easier to use and to get readings than tympanometry. However, each device is giving different information. The acoustic reflectometer is using a sonar wave and relies on the thickness of the eardrum and middle-ear fluid to provide a readout that is abnormal. But if the eardrum is thickened from past infections, then the readout is abnormal. Also, if the fluid behind the eardrum is thickened (and not air), then the readout is abnormal. So we fully agree with the interpretation of Dr. Ruohola's group.
To diagnose an ear infection or absence of an ear infection, the clinician must visualize the eardrum and often also needs to apply pneumatic otoscopy to be most accurate. Acoustic reflectometry and tympanometry are adjunctive tools that may assist the clinician in uncertain cases and encourage an immediate re-examination if the readout contradicts the first examination impressions.
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