Acute Otitis Media: Part I. Improving Diagnostic Accuracy
Am Fam Physician. 2000 Apr 1;61(7):2051-2056.
This is part I of a two-part article on acute otitis media. Part II, “Treatment in an Era of Increasing Antibiotic Resistance,“ will appear in the next issue.
Acute otitis media is overdiagnosed. Symptoms are neither sensitive nor specific for the diagnosis of otitis media; fever and ear pain are present in only one half of patients. Undue reliance on one feature—redness of the tympanic membrane—and failure to assess tympanic membrane mobility with pneumatic otoscopy contribute to inaccurate diagnoses. Adequate visualization of the tympanic membrane is often impaired by low light output from old otoscope bulbs and blockage of the ear canal by cerumen. Distinguishing acute otitis media from otitis media with effusion is clinically important because antibiotics are seldom indicated for the latter condition. A key differentiating feature is the position of the tympanic membrane: it is usually bulging in acute otitis media and in a neutral position or a retracted position in otitis media with effusion. Tympanometry and acoustic reflectometry can be useful adjunctive tools to confirm the presence of fluid in the middle ear. Selective use of tympanocentesis in cases of refractory or recurrent middle ear disease can help guide appropriate therapy and avoid unnecessary medical or surgical interventions.
Every family physician is well aware of the diagnostic dilemma posed by an ill child who may or may not have acute otitis media. The signs and symptoms classically associated with acute otitis media have unimpressive sensitivity and specificity when subjected to rigorous analysis (Tables 11and 22). Moreover, in even the most experienced hands, an adequate physical examination of the ears can be difficult to perform because of common problems such as cerumen blockage of the auditory canal, an uncooperative toddler or an exasperated parent.
TABLE 1 Symptoms of Acute Otitis Media in 363 Children
Symptoms of Acute Otitis Media in 363 Children
|Symptom||Percentage of children|
Cough or rhinitis
Reprinted with permission from Ruuskanen O, Heikkinen T. Otitis media: etiology and diagnosis. Pediatr Infect Dis J 1994;13(suppl):S23–6.
TABLE 2 Tympanic Membrane Signs of Acute Otitis Media
Tympanic Membrane Signs of Acute Otitis Media
|Tympanic membrane appearance||Percentage of ears (n = 528 ears)|
Bulging or full
Adapted with permission from Arola M, Ruuskanen O, Ziegler T, Mertsola J, Nanto-Salonen K, Putto-Laurila A, et al. Clinical role of respiratory virus infection in acute otitis media. Pediatrics 1990;86:851.
Compounding the dilemma is the less than robust effect of antibiotics on acute otitis media. Extensive research during the past two decades has led to doubts about the use of antibiotics for treatment of otitis media. Some physicians' organizations no longer recommend the routine use of antibiotics in uncomplicated acute otitis media.3 The busy clinician enters the examination room with all of these difficulties in mind and is often sorely tempted to overdiagnose acute otitis media.
Consequences of Overdiagnosis
The consequences of overdiagnosis, however, must be considered. A prescription for antibiotics almost always follows the diagnosis. A patient who does not actually have acute otitis media is unnecessarily placed at risk for the occasional adverse consequences of antibiotic therapy. More importantly, if the patient is declared not to have responded satisfactorily to the medication, use of broader spectrum antibiotics is advocated at a follow-up examination. Repeated episodes of acute otitis media, particularly episodes that appear not to have responded to antibiotics, often lead to referral for tympanostomy tube surgery, sometimes with adenoidectomy.
Overdiagnosis of acute otitis media can have an impact in clinical research trials because it results in an overestimation of efficacy for all treatments and a blurring of any actual differences in efficacy between treatments. Standardized and stringent criteria for the clinical diagnosis of acute otitis media and a characterization of improvement or cure are lacking. A literature review of 26 clinical trials revealed 19 sets of criteria for making the diagnosis of acute otitis media.4 Some of the children in these studies did not actually have acute otitis media but had otitis media with effusion or no disease at all. After enrollment in an antibiotic study, “ear infection” in such children probably would be classified as cured or improved following a course of antibiotic treatment, even though they did not have acute otitis media in the first place.
The classic findings of acute otitis media, such as fever and earache, are sometimes absent even in cases confirmed by tympanocentesis. A bulging, red, immobile tympanic membrane is highly associated with acute otitis media. However, many physicians rely on redness of the eardrum as the main diagnostic clue. Crying (and most young children cry when their ears are examined), removal of cerumen with associated irritation of the auditory canal and fever can all cause redness of the eardrum in the absence of middle ear infection. Most of all, when a parent brings a child to the physician because of irritability, rhinorrhea and fever, the temptation is great to see at least a little bit of redness or fluid behind the eardrum as justification for an antibiotic prescription.
Definitions of Acute Otitis Media and Otitis Media with Effusion
Distinguishing episodes of otitis media as acute suppurative otitis media or otitis media with effusion is important for clinical decision making.5 Acute otitis media is defined by the presence of symptoms of acute illness and signs (full or bulging) of a tympanic membrane under positive pressure. Otitis media with effusion is defined by the absence of symptoms and signs of acute infection (other than reduced hearing) and the presence of signs (retracted or neutral position) of a tympanic membrane under negative pressure or no pressure and fluid in the middle ear space. Antibiotics are traditionally indicated for acute otitis media but may often be appropriately deferred if otitis media with effusion is present, in agreement with recommendations by the U.S. Agency for Healthcare Research and Quality (formerly called the Agency for Health Care Policy and Research).5
Interpreting Symptoms and Signs
The reliability of symptoms and signs in the diagnosis of acute otitis media was studied in 354 children who were seen consecutively by pediatricians, otolaryngologists or family physicians because of any kind of acute respiratory illness.6 The symptoms and signs observed at home were recorded by the parents before the visit, and the findings of the physical examination were recorded by the physician. Acute otitis media was diagnosed in 191 patients (54 percent).
The most important symptoms that increased the likelihood of acute otitis media were ear-related symptoms, such as earache, rubbing of the ear or a report by older children of the ear feeling blocked. However, only two thirds of the children younger than two years of age with acute otitis media had ear-related symptoms. Although fever, earache, crying and irritability, alone or in combination, were present in 90 percent of the children with acute otitis media, these same symptoms were present in 72 percent of the children who did not have acute otitis media. Furthermore, the duration of the symptoms was not markedly different in children with acute otitis media compared with the duration in children who had other diagnoses.
In a study of 302 children younger than four years of age,7 40 percent of the children with acute otitis media never complained of or never had symptoms of an earache. Fever was not present in 31 percent, and sleep was not disturbed in one half of the children with acute otitis media.
As with symptoms in acute otitis media, the findings on physical examination also lack reliability. In a study of pneumatic otoscopic findings in 85 infants and children,8 a poorly mobile, bulging, yellow and opacified tympanic membrane was the otoscopic finding that was most predictive of acute otitis media, but this appearance was noted in only 19 percent of the patients. The color of the tympanic membrane did not correlate at all with the presence or absence of a pathogen isolated from the middle ear exudate.
One analysis demonstrated that a bulging, opaque, immobile tympanic membrane had a 99 percent predictive value for acute otitis media compared with the findings at tympanocentesis (Table 3).9 The presence of a normal or retracted position of the tympanic membrane, with slightly impaired or normal mobility, was unlikely to be associated with acute otitis media unless the fluid behind the membrane was cloudy. A slightly red tympanic membrane with a normal position and normal mobility had a predictive value of only 7 percent for acute otitis media.
Predictive Value of Position, Color and Mobility of the Tympanic Membrane in Acute Otitis Media
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In a study that compared tympanometry and pneumatic otoscopy with findings of myringotomy in 86 children (163 ears), the sensitivity and specificity of a flat tympanogram for the presence of a middle ear effusion were 90 and 86 percent, respectively.10 Pneumatic otoscopic findings were 93 percent sensitive and only 58 percent specific for effusion.
In a study of acoustic reflectometry and other diagnostic techniques for the detection of middle ear effusion in 299 ears,11 a spectral gradient angle of less than 49 on the acoustic reflectometry instrument was found in 88 percent of the children with middle ear effusion. In contrast, when the spectral gradient angle was more than 95, only 17 percent of the children had middle ear effusion. Acoustic reflectometry and tympanometry compared favorably in predicting the presence or absence of middle ear effusion. A review of six studies (which included 12,333 ears)12 revealed that the sensitivity of acoustic reflectometry varied from 54 to 94 percent and the specificity ranged from 59 to 83 percent.
How to Improve Diagnostic Accuracy in Acute Otitis Media
Adequate otoscopic illumination is critical for the diagnosis of acute otitis media. In a study of otoscopes used by 96 private practice physicians,13 approximately one third of the devices were found to have a suboptimal output of light. The light output of each unit was measured initially; a new bulb or, when possible, a new battery was then put into the unit, and the degree of illumination was remeasured. Replacement of the bulb restored adequate illumination in 80 percent of the otoscopes. One third of the physicians reported changing the bulbs less often than every two years (as is recommended), and almost one half of the rechargeable batteries that were inspected were found to be outdated.
The tympanic membrane cannot be adequately seen when it is partially occluded by cerumen. Cerumen removal is essential for visualization of the tympanic membrane, and some type of curette should be used to remove cerumen. If the wax is dry or deep in the auditory canal, cerumenolytics and/or warm water irrigation may be necessary. Parents should be taught to restrain an uncooperative child for wax removal and proper examination of the tympanic membrane.
Pneumatic otoscopy has been advocated as an adjunct to assist in achieving diagnostic accuracy of acute otitis media,8–11,14–19 yet most physicians find it inconvenient or remain unconvinced of its value. To successfully cause movement of the tympanic membrane, the ear speculum must create an air seal against the external auditory canal, which is seldom possible with the standard disposable speculum. A rubber sleeve over the speculum may reduce the discomfort of the examination. All otoscope manufacturers sell inexpensive sets of cuffed ear speculums that can be used in performing insufflation.
Four characteristics of the tympanic membrane—position, mobility, color and degree of translucency—should be evaluated and described in every examination. The normal tympanic membrane is in the neutral position (neither retracted nor bulging), pearly gray, translucent and responding briskly to positive and negative pressure, indicating an air-filled space. An abnormal tympanic membrane may be retracted or bulging and immobile or poorly mobile to positive or negative air pressure.
The position of the tympanic membrane is a key for differentiating acute otitis media and otitis media with effusion. In acute otitis media, the tympanic membrane is usually bulging. In otitis media with effusion, it is typically retracted or in the neutral position. The tympanic membrane can be thickened in both acute otitis media and otitis media with effusion, thereby reducing visibility through it. A yellow or grayish middle ear effusion can be seen behind the tympanic membrane in either condition.
TYMPANOMETRY AND ACOUSTIC REFLECTOMETRY
Tympanometry and acoustic reflectometry each have attributes that make them valuable in providing information about the possible presence of a middle ear effusion.11,12,19 Neither is a perfect instrument, and both have some limitations. Both instruments have portable models, allowing them to be carried from one examination room to another. Acoustic reflectometry has the advantage of not requiring a seal within the ear canal, which improves its usefulness in a child who is not cooperative. Tympanometry provides additional information about actual pressures within the middle ear space.19 Both instruments can be connected to printers, thereby providing a permanent record of the readings for comparison at subsequent examinations and for documentation to health insurers.
The gold standard for the diagnosis of acute otitis media in clinical trials is tympanocentesis for determination of the presence of middle ear fluid, with subsequent culture for identification of causative pathogens.16–18,20,21 For obvious reasons of cost, effort and lack of availability of tympanocentesis, there are no consensus guidelines calling for the routine use of tympanocentesis in the management of acute otitis media and otitis media with effusion. In selected cases of refractory or recurrent middle ear disease, however, tympanocentesis can serve to improve diagnostic accuracy, guide treatment and avoid unnecessary medical or surgical interventions. A recent report from the Centers for Disease Control and Prevention (CDC) working group on drug-resistant Streptococcus pneumoniae20,22 includes an option for tympanocentesis versus empiric second-line antibiotic therapy in cases where initial antibiotic therapy has failed.
Few experiences are more self-educating than to diagnose acute otitis media by the history and ear examination and then encounter the absence of fluid on tympanocentesis. Although few family physicians are using this procedure in office practice, it is no more difficult than many other commonly performed office surgeries. The procedure has a satisfactory safety record. For example, with more than 750 procedures performed in our office during the past 10 years, only four instances have occurred of minor complications (drainage of fluid or blood in the middle ear), all of which resolved without intervention.
Proper restraint of the patient and excellent visualization of the tympanic membrane are essential when tympanocentesis is performed. Mild sedation may also be helpful in some cases.23
The average physician may examine the ears of more than 30 patients each working day, five days per week for about 40 weeks per year, for a total of more than 14,000 ears examined each year. Nevertheless, the medical literature suggests that acute otitis media is frequently over-diagnosed. Good otoscopic illumination, cerumen removal and attention to the position and mobility of the tympanic membrane (rather than only to the color) are important for an accurate diagnosis. Tympanometry or acoustic reflectometry can add information in some cases, and tympanocentesis remains the gold standard for diagnosis in selected difficult cases.
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