Pediatric Residents’ Journal Club February 5, 2009 Sara Szkola

1. Paula Louise Thompson, Ruth E. Gilbert, Paul F. Long, Sonia Saxena, Mike Sharland, and Ian Chi Kei WongPediatrics 2009; 123: 424-430 Effect of Antibiotics for Otitis Media on Mastoiditis in Children: A Retrospective Cohort Study Using the United Kingdom General Practice Research Database Pediatric Residents’ Journal Club February 5, 2009 Sara Szkola

2. Background • Otitis media is the main reason children visit their doctor in the UK • Though most cases of otitis media are self-limiting, rarely children can go on to develop complications such as mastoiditis • Antibiotic prescriptions for otitis media have decreased in recent years, and other studies have documented a concurrent increase in hospital admissions (1, 2, 3) • This study aimed to determine if this is a causal relationship between decreased antibiotic use and increased complications (ie, mastoiditis), or if it is due to changes in “access to services, referral patterns and coding of routine data” • That is, does it make sense to give antibiotics for otitis media for the purpose of preventing mastoiditis?

3. Study Design • Data were drawn from the General Practice Research Database, a database that draws from practices all over the UK and includes information on all active patients • Children aged 3 months to 15 years who were in this database from 1990-2006 were included • 2 exclusions: children who weren’t with “up to standard” practice (MD not recording all data), and “temporarily registered” children (ie, 1 visit to different MD than their own)

4. Study Design Continued

5. Data Analysis • Age specific incidence rates (along with calendar-year specific incidence rates) for mastoiditis with and without otitis media were calculated per 1000 child years at risk • Incidence rates were also calculated for otitis media and for antibiotic-prescribing for otitis media • Then they calculated the relative risk of children with otitis media developing mastoiditis with and without antibiotc treatment

6. What are all these statistics? • Incidence rate per 1000 children years means the number of new cases per unit of person-time at risk. That is…. If the incident rate is 10 per 1000 children years, then in a population of 1000 children, 10 would be expected to develop otitis media in 1 year. If you observed the population for 2 years instead of 1, then 20 would be expected to develop otitis media (you divide the number of cases by the number of years).

7. What did they find out? • Of the approximately 2.6 million children in the database, 854 had mastoiditis. Only about 1/3 (288 children) of this group had preceding otitis media. • There were approximately 1.2 million episodes of otitis media; of these children, 288 went on to develop mastoiditis. • For the children with otitis media, antibiotic treatment lowered the risk of mastoiditis from 3.8/10,000 to 1.8 per 10,000.

8. More interesting trends… • They also found that while the incidence of antibiotic prescribing for otitis media steadily decreased over the time period of the study (1990-2006), the incidence of mastoiditis remained stable.

9. What does this mean for me? • You would have to treat an average of 4831 episodes of otitis media to prevent one episode of mastoiditis • Decreased prescribing of antibiotics did not cause an increase in mastoiditis • Antibiotics should not be routinely given for otitis media for the purpose of preventing mastoiditis

10. Critical Review

11. Was the type of study strong? • Yes • This article contained a combination of cohort (otitis media group) and case control (mastoiditis group) studies, both appropriate to look for causation

12. Was the assessment of exposure and outcome free of bias? • Mostly…. • The investigators weren’t determining who had mastoiditis or otitis media, and so couldn’t influence those results • But, the coding and diagnosis may vary among practices (ie, coding for otitis media vs URI) • Also, not everyone who was prescribed antibiotics likely took them

13. Was the association both significant and clinically important? • It was statistically signifcant, but… • As the authors clearly mention, not very clinically important, because the number needed to treat for otitis media to prevent mastoiditis is too high to be practical • While their results won’t likely change the trend of prescribing less antibiotics for otitis media, they can make us feel better that we aren’t putting patients at very high risk for mastoiditis

14. Was the association consistent across studies? • Yes and No • Other studies found similar rates of mastoiditis in the UK • However, other studies also pointed to mastoiditis peaking in children ages 1-4, while this study found the highest incidents in adolescents

15. Was the cause shown to precede the effect? • Yes • In both the mastoiditis group and the otitis media group, otitis media was clearly shown to precede the mastoiditis • In addition, antibiotic administration for otitis media preceded mastoiditis

16. Was there a dose-response relationship • Not applicable to this article, though it would have been interesting to investigate incidence of mastoiditis with high-dose vs low-dose antibiotics, or with severity of otitis media

17. Strengths of this Article • Large sample size of 2.6 million children • Long period of time which allowed documentation of trend of decreased antibiotic use with stable mastoiditis rates

18. Weaknesses of This Article • Coding practices can vary among practices • Diagnosis can vary among practices • Did not define high risk group for which antibiotics should be given to prevent mastoiditis

19. Take Home Points • Helpful article that will not necessarily change practice, but… • We can be reassured that in general we are not putting children at very high risk for mastoiditis if we do not give antibiotics for otitis media

20. Acknowledgments • Thank you to Dr. Quinlan and Dr. Goldstein for their help in this journal club

21. References 1) Little P, Watson L, Morgan S, Williamson I. Antibiotic prescribing and admissions with major suppurative complications of respiratory tract infections: a data linkage study. Br J Gen Pract. 2002; 52(476):187-193 2) Majeed A, Williams S, Jarman B, Aylin P. Prescribing of antibiotics and admissions for respiratory tract infections in England. Br Med J 2004; 329 (7471): 879. 3) Sharland M, Kendall H, Yeates D, et al. Changes in antibiotic prescribing in general practice and hospital admissions for quinsy, mastoiditis and rheumatic fever in children. Br Med J. 2005; 331 (7512):328-329.