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Culture-negative AOM data may affect efficacy studies and treatment strategies
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A recently published assessment of successful antibiotic treatment rates for acute otitis media (AOM) revealed that the inclusion of culture-negative AOM patients into clinical studies involving culture-positive AOM patients may falsely improve results.
Researchers in southern Israel conducted 11 double-tympanocentesis antibiotic efficacy studies involving 209 children with culture-negative AOM and 879 children with culture-positive AOM aged 3 to 36 months between 1994 and 2004.
At the end of four to six days of treatment, researchers noted 947 children were either cured or had improved AOM symptoms. Results indicated that the overall success rate was higher in children with culture-negative AOM (90%) when compared with children with culture-positive AOM (86%). Researchers also said there was a 9% reduction in the total clinical failure rate after inclusion of children with culture-negative AOM in data analysis.
Additionally, the success rate for children with culture-positive AOM depended on bacteriologic eradication.
The researchers said that past efficacy studies involved administration of full courses of antibiotic treatment to all patients with AOM despite the results of middle ear cultures. They concluded that not differentiating between culture-negative and culture-positive AOM patients skewed these study results.
“This creates an interpretation bias, overemphasizing the successful outcome of children treated with antibiotics that have low bacteriologic activity,” wrote Eugene Leibovitz, MD, and other researchers from Soroka University Medical Center, Ben Gurion University of Negev, Beer Sheva, Israel.
The researchers also pointed to the construction of their study to elaborate upon their conclusions. They used a hypothetical antibiotic efficacy study where they analyzed two drugs with different bacteriologic efficacy (90% and 60%) to elaborate upon their conclusions.
“In this model, we chose to analyze the clinical outcome as function of the percentage of patients with culture-negative AOM initially enrolled (16.7% and 50%) from all patients enrolled, and showed how an increase in the number of culture-negative AOM cases enrolled leads to a major dilution of the results by considerably decreasing the overall rates of clinical failure and making the drug with low bacteriologic efficacy appear much more efficacious.”
As a result of their findings, the researchers recommended that culture-negative patients should not be included in future antibiotic efficacy studies. – by Melissa Foster
Leibovitz E. Pediatr Infect Dis J. 2009;28:1105-1110.
AOM with middle ear fluid containing bacterial pathogens differs clinically and in production of inflammatory mediators, as these authors note. The questions arise, however, whether these differences are sufficient to not treat those children with a clinical profile of culture-negative AOM, and would their outcome be similar to those treated with antibiotics? If the wealth of data collected from these 11 double-tympanocentesis antibiotic efficacy studies could help answer this question, it would be interesting and important as most AOM in the world is treated on the basis of clinical findings and history– or less.
– Caroline B. Hall, MD
Infectious Diseases in Children Editorial
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