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April 2003 An extraordinary amount of attention has been focused recently on the management of acute otitis media (AOM). Two papers have identified some major flaws in the design and conduct of most clinical trials in AOM.
The most critical and contentious issue at present is the definition of AOM that is used when recruiting patients into studies comparing the efficacy of two antibiotics. If studies that evaluate the impact of antibiotic therapy on the clinical course of children with AOM have weak definitions of AOM, (which allow the inclusion of children more likely to have otitis media with effusion that AOM), recipients of placebo will not respond much differently than those who receive antibiotic. Investigators generally agree that there are two essential findings for AOM. The first is evidence of middle ear effusion demonstrated by pneumatic otoscopy. The diagnostic criteria for middle ear effusion includes impaired or absent mobility of a tympanic membrane (TM) (or visualization of a distinct air/purulent fluid level). Second is evidence of acute inflammation of the opacified TM, especially bulging of the TM contour. The exact color of the TM is much less important than bulging, and impaired TM mobility. Indeed, verified AOM can occur with bulging opacified white, gray, yellow and of course red TMs. How does the clinician define a full or bulging TM? In this column there have been articles on proper scheduled maintenance of the office otoscope, and techniques for removal of cerumen, restraint of children and pneumatic otoscopy. Although the importance of noting whether the TM is bulging or full has been stressed previously, a step-by-step approach to defining the terms “fullness or bulging” of the TM has not been undertaken.
After a normal TM is visualized, the examiner should direct his eye to the umbo, the most medial and central part of the TM. From the umbo, the examining eye should sweep upward along the manubrium (malleus handle) until the eye visualizes the lateral (short) process sitting somewhat akin to a scoop of ice cream on a handle. Behind the left TM, the lateral process is at 11 o’clock and behind the right TM it is at 1 o’clock. A completely bulging TM means that neither the manubrium nor the lateral process can be seen through the convex opacified TM. A partially bulging (full) TM means that the manubrium is obscured and most of the TM is convex. The faint outline of the lateral process of the manubrium can be visualized, particularly when positive pressure is applied to the surface of the TM through the pneumatic otoscope. A non-bulging, opacified, immobile TM in the neutral or retracted position, even when accompanied by constitutional signs of illness — fever, anorexia, nausea, irritability and vomiting — is not sufficient for a diagnosis of AOM. In the design of clinical studies comparing two different antimicrobials or an antimicrobial to placebo it is essential to have a stringent definition for cases of AOM. AOM must be distinguished from symptomatic otitis media with effusion (OME), a condition in which the middle ear effusion is usually sterile and does not benefit from antibiotic therapy. The failure to make this distinction has led to substantial overuse of antimicrobials by primary care physicians and very possibly is a major contributor to the antimicrobial resistance of respiratory bacterial pathogens.
Several recent meta-analyses have concluded that antibiotics exert only a modest benefit compared to placebo with AOM and that there has been no demonstrable superiority of any antibiotic compared to amoxicillin in the treatment of this condition. The most frequently cited meta-analysis, reported by Rosenfeld et al, included only randomized, controlled clinical trials. Their definition of AOM was “bulging or opacification of the tympanic membrane — with or without erythema — accompanied by at least one of the following signs and symptoms: fever, otalgia, irritability, otorrhea, lethargy, anorexia, vomiting or diarrhea.” That many of these children did not have AOM is likely. The exclusion of the sickest and youngest children, those most likely to benefit from antibiotics, biases these studies in the direction of “no difference.” Another recent meta-analysis was the Cochrane review. Three criteria were required for a study to be included in the Cochrane review: proper randomization, degree of follow-up and blinding. No attention was given to the definition of AOM as a criterion for inclusion. In the most recent meta-analysis, performed by the Southern California Evidence-based Practice Center, RAND for the Agency for Health Care Quality and Research, the definition of AOM had three components: presence of middle ear effusion, rapid onset and one or more signs or symptoms of inflammation. The signs of inflammation included fever, irritability, anorexia, vomiting or diarrhea. These constitutional signs of illness are non-specific for true AOM; therefore, this is a weak definition of AOM. None of the 80 studies included in the meta-analysis used all three components of the definition, and 35% used none. The experience that is frequently cited as evidence that “watchful waiting,” as practiced in the Netherlands, is a viable strategy, is that of Little and colleagues. In this study, 315 children between 6 months and 10 years of age with “acute red ear” were assessed in a randomized trial. Fifty-nine percent of the children were older than 3 years of age (although the peak age incidence of AOM is between 6 and 18 months of age), suggesting that this was not a random selection of children. Seven percent to 9% of the children had perforated TMs and only 46% had bulging TMs. In other words, 45% of children may not have actually had bacterial AOM. Overuse of antibiotics probably does not result from treatment of bona fide cases of moderately to severely painful AOM defined by a TM that is bulging and immobile. The FDA should insist on this precise definition of AOM for all clinical studies of the disease. Pediatric and family practice residency training programs must make a concerted effort to improve the diagnostic otoscopic skills of current and future generations of primary care providers. Some of those already in clinical practice are resisting their routine use of precise criteria for AOM. Please repeat after us: “A reddened TM with absent cone of light does not make a diagnosis of AOM.”
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