Tympanometry EDWARD ONUSKO, M.D., Clinton Memorial Hospital, Wilmington, Ohio Tympanometry provides useful quantitative information about the presence of fluid in the middle ear, mobility of the middle ear system, and ear canal volume. Its use has been recommended in conjunction with more qualitative information (e.g., history, appearance, and mobility of the tympanic membrane) in the evaluation of otitis media with effusion and to a lesser extent in acute otitis media. It also can provide useful information about the patency of tympanostomy tubes. Tympanometry is not reliable in infants younger than seven months because of the highly compliant ear canals of infants. Tympanogram tracings are classified as type A (normal), type B (flat, clearly abnormal), and type C (indicating a significantly negative pressure in the middle ear, possibly indicative of pathology). According to the Agency for Healthcare Research and Quality guidelines on otitis media with effusion, the positive predictive value of an abnormal (flat, type B) tympanogram is between 49 and 99 percent. A type C curve may be useful when correlated with other findings, but by itself it is an imprecise estimate of middle ear pressure and does not have high sensitivity or specificity for middle ear disorders. (Am Fam Physician 2004;70:1713-20. Copy- right© 2004 American Academy of Family Physicians.) titis media with effusion (OME) tympanic membrane should be performed is defined as fluid in the middle before tympanometry.6 Using pneumatic ear without signs or symptoms otoscopy with tympanometry improves of ear infection.1 Acute otitis the accuracy of diagnosis because many O media (AOM) is defined as the presence of abnormalities of the eardrum and ear canal middle ear effusion in conjunction with the that might cause an abnormal tracing can recent, abrupt onset of one or more signs be visualized. Determining the presence or symptoms of inflammation of the mid- of obstructing cerumen in the canal, per- dle ear.2 AOM is the most frequently diag- foration or ventilation tubes in the tym- nosed disease in children, and its treatment panic membrane, and characteristics of the results in more than 20 million antibiotic tympanic membrane (e.g., color, mobility, prescriptions annually in the United States.3,4 position, translucency) are helpful in corre- Frequently, AOM is overdiagnosed,5,6 and lating tympanometry findings with clinical failure to differentiate AOM from OME may disease.8,11,12 When comparing either test be the most common cause of unnecessary alone, pneumatic otoscopy has a better sen- antibiotic prescriptions.3 Numerous studies sitivity and specificity than tympanometry have shown that some physi- for the diagnosis of OME.1 The two tests cal findings commonly used to can be complementary, because pneumatic Using pneumatic otoscopy predict AOM, such as redness or otoscopy provides a qualitative measure of with tympanometry retraction of the tympanic mem- tympanic membrane mobility (i.e., does the improves the accuracy brane, have poor sensitivity and tympanic membrane move with insuffla- of diagnosis. specificity.7-9 The definitions for tion?) and tympanometry produces more AOM and OME require detect- quantitative information (e.g., numeric and ing the presence of middle ear effusion.1,2,10 graphic data about generated positive and The handheld tympanometer is a device negative pressures, absorption of acoustic that provides quantitative information on energy by the middle ear system, ear canal the function of structures and the pres- volume).11,13 ence of fluid in the middle ear. The graphic The American Academy of Pediat- display of this data is the tympanogram. rics (AAP)/American Academy of Family A pneumatic otoscopic examination of the Physicians (AAFP)/Agency for Healthcare November 1, 2004 ◆ Volume 70, Number 9 www.aafp.org/afp American Family Physician 1713 Downloaded from the American Family Physician Web site at www.aafp.org/afp. Copyright© 2004 American Academy of Family Physicians. For the private, noncommercial use of one individual user of the Web site. All other rights reserved. Contact [email protected] for copyright questions and/or permission requests. Research and Quality (AHRQ) guideline use of pneumatic otoscopy and tympanom- on OME recommends that performance of etry for diagnosing OME is poor.19 tympanometry be optional for confirming suspected OME.1,13 The guideline states that Efficacy “the accuracy of pneumatic otoscopy in rou- Family physicians can use and interpret tine clinical practice may be less than that tympanograms for more accurate clinical shown in published results because clini- decision making.8,20,21 The success rate for cians have varying training and experience. performing tympanometry (i.e., the ability When the diagnosis of OME is uncertain, to obtain a clinically useful tympanogram tympanometry or acoustic reflectometry tracing) is between 74 and 94 percent (com- should be considered as an adjunct to pneu- pared with a success rate of 85 to 91 percent matic otoscopy.” The Institute for Clinical for otoscopy).22 System Improvement concluded that tym- In a small Turkish study using confirmation panometry may be useful in establishing of middle ear effusion by myringotomy as the the diagnosis of OME, but that it usually gold standard, tympanometry had a posi- was not necessary for diagnos- tive predictive value and specificity of 96 and ing (or documenting resolution 92 percent, respectively; a negative predictive Tympanometry is not reli- of) AOM.14 The AAP/AAFP/ value and sensitivity of 96 percent each; and able in infants younger AHRQ guidelines for AOM a false-positive rate of 8 percent in detecting than seven months because require the documentation the presence or absence of middle ear fluid in the ear canals of infants of middle ear effusion for the normal appearing ears.23 The predictive ability are highly compliant. diagnosis of AOM by tympa- of tympanometry was lower, however, if the nometry, pneumatic otoscopy, otoscopic examination showed retraction or acoustic reflectometry, tympa- other signs of effusion, but myringotomy dem- nocentesis, or the visualization of fluid in onstrated the absence of middle ear fluid. the external ear canal with tympanic mem- In the 1994 AHRQ guidelines on OME, brane perforation.2 However, for OME and which were reaffirmed in 1997, the positive pre- AOM, pneumatic otoscopy is recommended dictive value of an abnormal (defined as a flat, as the primary tool for diagnosis of middle type B tracing) tympanogram was between ear effusion. 49 and 99 percent.13 The AHRQ reexamined Other guidelines advise using tympanom- the evidence regarding the diagnosis and etry to evaluate middle ear function in natural history of OME and published their infants suspected of having hearing disor- findings in May 2002.24 Of the eight diag- ders15 but not as a screening tool for periodic nostic studies reviewed (including portable pediatric health examinations.1,16,17 Tympa- tympanometry), the summary statement nometry is not reliable in infants younger recommends pneumatic otoscopy as the than seven months because the ear canals of preferred test (pooled sensitivity of 94 per- infants are highly compliant.17,18 In clinical cent and specificity of 80 percent). Another practice, adherence to practice guidelines for analysis was performed of five studies using portable tympanometry, and 31 studies using professional tympanometry. Among The Author the eight diagnostic methods, professional tympanometry (using a B or C2 curve as EDWARD ONUSKO, M.D., is associate director of the Clinton Memorial Hospital/ abnormal) tied with pneumatic otoscopy University of Cincinnati family practice residency program in Wilmington, Ohio. He is associate professor of clinical family medicine at the University of Cincinnati for the highest sensitivity at 93.8 percent College of Medicine. Dr. Onusko graduated from Case Western Reserve (95 percent confidence interval [CI]: 91.1 to University School of Medicine, Cleveland, and completed a residency in family 96.4 percent), compared with myringotomy medicine at University Hospitals of Cleveland. (Table 1).25 The diagnostic test with the Address correspondence to Edward Onusko, M.D., Clinton Memorial Hospital, highest specificity was professional tympa- Family Practice Residency Program, 825 W. Locust St., Wilmington, OH 45177 nometry (using static compensated acoustic (e-mail: [email protected]). Reprints are not available from the author. admittance at 0.1) at 94.1 percent (95 percent 1714 American Family Physician www.aafp.org/afp Volume 70, Number 9 ◆ November 1, 2004 Tympanometry TABLE 1 Summary of Meta-analysis for Diagnostic Comparisons The rightsholder did not grant rights to reproduce this item in electronic media. For the missing item, see the original print version of this publication. CI: 83.9 to 100 percent). The Canadian Task tive pressures into the ear canal. A microphone Force on Preventive Health Care reported in the instrument detects returning sound that tympanometry has sensitivity and spec- energy. Four useful pieces of objective data are ificity greater than 80 percent in predicting obtained by the tympanometer (Table 2).26-28 fluid found in the middle ear at surgery.16 Studies combining tympanometry with Interpreting Results clinical signs and symptoms have shown a Figures 1 and 2 depict various tympanogram sensitivity of 90 percent and a specificity of tracings based on variations of the original 75 percent in diagnosing OME.8 Liden and Jerger classifications.29 The middle curve in Figure 1 is from a normal ear. The Using the Tympanometer tympanogram curve has a normal maximum Portable tympanometers (resembling stan- height that occurs at a pressure close to zero dard otoscopes) and desktop instruments are and the width of the curve is normal. This available. The probe is placed snugly in the is referred to as a type A tracing. In this fig- external ear canal. A sound stimulus generator ure, the ear canal volume is normal. Figure transmits acoustic energy into the canal while 1 also has a curve that demonstrates a high a vacuum pump introduces positive and nega- peak height, labeled as type AD.