Does Tympanometry Predict Antibiotic Usage in Acute Otitis Media?
Condition: Acute Otitis Media
MeSH terms: Otitis; Otitis Media
Study type: Observational

Summary: 
      Due to recent efforts to decrease antibiotic overuse, and reports of high rates of
      spontaneous resolution for clinically diagnosed Acute Otitis Media(AOM), most physicians now
      wait 48-72 hours before starting antibiotics for common ear infections. The investigators are
      interested to see if those patients with documented middle ear effusions, as determined by
      tympanometry, have higher rates of eventual antibiotic usage than those with normal
      tympanometry results. If there is a significant disparity between those with a positive
      tympanogram and those without the investigators may be able to identify a group that will
      benefit from antibiotics and a group that would not need treatment.
    

Detailed description: 
      INTRODUCTION Acute Otitis Media (AOM) is the most common childhood infection for which
      antibiotics are prescribed.{1-2} Several important factors have altered the prescription
      practices for AOM in the past decade. North America has seen an epidemic of microbial
      resistance, attributable in a large part to the over-prescription of antibiotics.{3-4}
      Evidence has shown that AOM is commonly over diagnosed and antibiotics are prescribed
      unnecessarily.{5-7} In addition a number of studies comparing antibiotic treatment to
      placebo, although proving superiority for antibiotic treatment, had very high rates of
      resolution with placebo. A meta analysis of 7 RCT's show a 73% success rate for Amoxicillin
      versus 60% for placebo.{8}

      These results prompted interest in a watch and wait strategy for the treatment of AOM for
      children 6 months to 10 years of age. Three important studies were performed assessing the
      outcomes of delaying antibiotics for 48-72H, two in primary care{9-10} and one in a pediatric
      emergency department.{11} All three showed no difference in outcomes with 2-4 week follow-up.
      There was a significant reduction in antibiotic usage with the watch and wait approach, a
      reduction of about 70%. These studies led both the American Academy of Pediatrics and the
      Canadian Pediatric Society to recommend adopting a conservative non-antibiotic treatment
      strategy for AOM in the first 48-72H.{12} However in early 2011, 2 papers were published that
      suggested that antibiotic use in AOM was beneficial.{13, 14} What set both of these two
      papers apart from other papers was the definition of acute otitis media: in one study the
      children were enrolled by study clinicians who were otoscopists who had successfully
      completed an otoscopic validation program, in the second study middle ear fluid had to be
      present by means of pneumatic otoscopy. The question then arises, is the treatment of otitis
      media really a question that concerns the treatment, or is it a question of diagnosis? The
      published correspondence that these two papers generated, suggested that diagnosis of AOM is
      indeed a concern. A technique named tympanometry could prove to be useful.

      Tympanometry is a well established technique for documentation of middle ear effusion.
      Tympanometry measures the compliance of the tympanic membrane over a range of pressures. A
      graphic curve is generated which can be compared to normals or examples of pathologic
      conditions. Primary care physicians have used this technique successfully among children with
      and without a diagnosis of AOM.{15} Two studies involving tympanometry and otitis
      media{16-17} have shown tympanograms consistent with clear middle ear effusion(Type B) in
      50-60% of patients clinically diagnosed with AOM. This strongly suggests that AOM is being
      over diagnosed! Interestingly Spiro et al showed that rates of antibiotic prescription were
      not different in physicians who were aware of tympanogram results and those who were blinded.
      This indicates a lack of knowledge around the impact on outcome of the initial tympanogram.

      Currently at the Stollery, (and as suggested by CPS and AMA) well children who are diagnosed
      with AOM are given a prescription for antibiotics, but told to wait 48 hours before filling
      them, in the expectation that many of these children will have a complete resolution of their
      symptoms. They are encouraged to take analgesics to keep them comfortable. However, the
      current state of knowledge indicates that antibiotics provide superior symptom control in the
      first 24-48H and provide superior resolution rates to placebo in clinically diagnosed AOM.
      The delayed antibiotic strategy has similar long term outcomes to immediate antibiotic
      treatment. It is not clear if patients with middle ear effusion documented by adjunctive
      tests, such as tympanometry represent a distinctly different group than those diagnosed by
      observation of the tympanic membrane only. Spiro's study indicates that physicians do not
      know and therefore are not changing their practice on the basis of tympanogram results.

      This then brings us to the investigators' primary research question. Are those children aged
      6 months to 16 years who attend the Stollery Emergency Department and are diagnosed with AOM
      (and sent home with conservative management) more likely to fill a prescription for
      antibiotics over the next 7 days if their tympanogram is type B rather than types A or C?

      The investigators propose an observational study, within a watch and wait strategy, to
      determine if patients clinically diagnosed with AOM and having a type B tympanogram have
      higher rates of eventual antibiotic usage. Secondary outcome measures would include symptoms
      of pain, fever and impaired sleep than those without clear evidence of middle ear effusion.

      If those patients with a B type tympanogram have a high rate of eventual antibiotic usage,
      delaying their treatment is not significantly reducing our overall antibiotic usage.
      Furthermore, the investigators could reduce the pain suffered by these patients in those
      first 48-72 hours. The corollary to this may be that those patients with other tympanogram
      patterns may have comparatively low need for antibiotics. This study would help to more
      accurately identify those patients likely to derive significant benefit from antibiotic
      treatment for AOM.

      PROJECT DESIGN AND WORK PLAN

      Design: The study is a non-interventional analysis of outcome. This is an observational
      cohort study.

      Intervention and sampling method: All patients diagnosed with OM will be approached for study
      enrolment within the hours which an RA is available. Tympanometry will be conducted on every
      participant in both ears. The clinician will not be privy to the result of the tympanogram.
      The tympanograms will be assigned a B or A/C shape, upon review by the principle
      investigators. In cases of disagreement a third reviewer will review the tympanogram.
      Patients will be followed with a phone call in 3 days and again at 8 days. They will be asked
      to rate their symptoms (Acute Otitis Media-Severity of Symptom Scale){18}, in addition to
      specific scripted interview questions for the study (under development) including a
      determination of antibiotic usage for the infection. The investigators will also review the
      provincial pharmacy database to confirm if antibiotics prescriptions were filled.

      Training: Research assistants will receive one-on-one training with the principal
      investigators on tympanography technique.

      Recruitment: Updates regarding the study will occur at the monthly staff meetings, posters
      describing the study will also be placed throughout the ED. Research Assistants will be
      visible in the department and will remind staff of the study.

      Primary Outcome: Are those children aged 6 months to 16 years who attend the Stollery
      Emergency Department and are diagnosed with AOM (and sent home with conservative management)
      more likely to fill a prescription for antibiotics over the next 7 days if their tympanogram
      is type B rather than types A or C? Secondary Outcomes: Does a type B tympanometry curve
      predict increases in (1)Reported Pain (2)Analgesic use (3)Fever (4)Sleep Disturbance (5)Oral
      intake versus type A/C tympanograms (6) Proportion of patients diagnosed with OM who have
      either type A or type A and C tympanograms.

      Sample Size: A logistic regression will be performed using antibiotic use in 7 days as the
      dependent variable. Given 4 independent variables, the investigators need at least 40 (80
      would be ideal) subjects who fill the antibiotic prescription. Enrolling 137 patients would
      give us an alpha and Beta each of 0.05, and would allow us to do Chi Squared test looking at
      a two by two table of Antibiotic (Yes or No) vs Tympanometry Graph (Type B vs other).

      Analysis: Antibiotic use in the 7 days following enrolment will be analyzed by logistic
      regression. Independent variables will include age, Tympanogram type A/C, Viral upper
      respiratory symptoms for ≥ 5days prior to presentation to the ED, and pain requiring
      analgesia in the Emergency or at home within 6H of presentation. Quantitative and qualitative
      data will be described. Antibiotic drug data will be checked in NetCare to see if there is a
      discrepancy between verbal reports and NetCare.

      Feasibility: Data from the investigators' emergency department indicates over 900 children
      per year present with AOM, and over the past 6 months of winter (Oct-Mar) there have been
      about 540. Based on previous results {9-11} the investigators predict an antibiotic usage
      rate of 30%. To collect 40 patients who fill a prescription for antibiotics the investigators
      will need 135 patients with otitis. If antibiotic usage rates are higher this number will
      decrease. Accounting for about a 15% drop out rate the investigators will need to enroll
      about 155 children. Conservatively assuming recruitment of 30% of children with AOM the
      investigators anticipate 24 weeks to reach the investigators' sample size.
    

Intervention name(s): Tympanometry
Intervention type(s): Procedure
Intervention description(s): All patients enrolled with receive a tympanogram. There will be no difference between the follow up in the groups based on the tympanometry results. The study is simply observational
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        All children, aged 6 months to 16 years, with clinically diagnosed Otitis Media in the
        Pediatric Emergency Department of the University of Alberta Hospital, in whom the clinician
        decides to adopt a delayed antibiotic strategy (ie a period of 48-72H observation with
        antibiotics given only if symptoms are not resolving).
      
Keywords: Otitis Media; Tympanometry