Abstract
BACKGROUND. Reported trends regarding the incidence of otitis media and antibiotic prescription rates are inconsistent.
OBJECTIVE. Our goal was to assess changes in incidence of consultation rates, antibiotic prescription, and referral rates for otitis media in children over the years 1995–2003.
METHODS. A cohort study including all children aged 0 to 13 years within the research database of the Netherlands University Medical Center Utrecht Primary Care Network covering the period 1995–2003. Otitis media diagnoses were recorded according to the International Classification of Primary Care codes and antibiotic prescription according to the Anatomic Therapeutic Chemical Classification System codes. Otitis media incidence rates were calculated as episodes per 1000 person-years. Antibiotic prescription and referral rates were calculated per 100 otitis media episodes.
RESULTS. From 1995 to 2003, the overall general practitioner consultation rates for acute otitis media and otitis media with effusion declined by 9% and 34%, respectively. In children aged 2 to 6 years and those aged 6 to 13 years, the incidence rates of acute otitis media and otitis media with effusion declined by 15% and 41% and 40% and 48%, respectively. In children <2 years of age, the incidence rates of acute otitis media and otitis media with effusion increased by 46% and 66%, respectively. Antibiotic prescription rates for acute otitis media and otitis media with effusion increased by 45% and 25%, respectively. The referral rate for acute otitis media did not change, whereas the referral rate for otitis media with effusion increased by 45%.
CONCLUSIONS. Consultation rates for otitis media have changed considerably over the last decade, and so have antibiotic prescriptions and specialist referrals. The rising antibiotic prescription rate for otitis media causes concern, because this may induce increasing medical costs and antibiotic resistance.
Otitis media (OM) is one of the most common infectious diseases in children and a major cause of doctor consultations and antibiotic prescriptions.1,2 Direct and indirect costs are high: in the Unites States, direct costs associated with OM are estimated at about $4 billion per year.3
Population-based studies from both the Unites States and Europe suggest that the incidence of OM has increased over the past 2 decades. Lanphear et al4 have reported a 44% increase in the prevalence of recurrent OM in children in the United States from 1981 to 1988, with the greatest increase in infants <12 months of age. In Finnish children, the incidence of acute OM (AOM) increased by 68% from 1978–1979 to 1994–1995.5 Conversely, Fleming et al6 reported a reduction in the incidence of respiratory tract infections, including OM, presenting to United Kingdom doctors during the years 1994–2000. Otters et al7 found comparable results in a comparison of the incidence of OM in Dutch children in 1987 and 2001.
Antibiotic prescription rates for OM vary from 31% in the Netherlands to 98% in both the United States and Australia.8 Recent studies from the United States,9,10 however, suggest a decline in the antibiotic prescribing rates for respiratory tract infections, including OM, whereas this rate seems to increase in the Netherlands.11
So far, in most studies on trends in incidence of OM and antibiotic prescription, comparisons were limited to rates in 2 years, and the effect of age on incidence of OM was not included. Such data may be insufficient to guide health educational programs for doctors and patients. Therefore, data obtained by continuous surveillance for a long period and in different age groups would be particularly relevant. The purpose of this study was to evaluate changes in consultation rates for OM and its management in children over recent years.
METHODS
Setting/Design
All data for this retrospective cohort study were obtained from the computerized medical database of the University Medical Center Utrecht Primary Care Research Network, which includes information on a cumulative population of ∼60000 patients over the years 1989–2004. The main characteristics of this patient population are similar to the Dutch population as a whole.12 From 1995 onwards, medical data of all patients enlisted in the 6 participating primary care centers have been recorded using a uniform, structured, contact registration format in the computerized general practitioner (GP) information system, ELIAS (ISoft, Nieuwegein, the Netherlands). ELIAS is one of the most commonly used GP information systems in the Netherlands.13 For research purposes, the following data were recorded systematically for all patients: demographics (date of birth, gender, and health insurance cover), type of GP contact, symptoms, signs, and diagnoses encoded according to the International Classification of Primary Care (ICPC) coding.14,15 ICPC is a comprehensive classification for primary care and has been used extensively in some parts of the world, notably in Europe and Australia. It allows classifications of 3 important elements of the health care encounter: reasons for encounter in the patient's view, assessment (diagnoses of problems) labeled in the health care provider's perspective, and process of care (decision, action, plans). The participating GPs received continued medical education regarding the correct coding of diagnostic information according to the ICPC coding system. More than 90% of contacts received an ICPC code, and accuracy seemed high. Furthermore, drug prescriptions are recorded in the database, including the drug name and Anatomic Therapeutic Chemical Classification System code.16 Finally, hospital referrals were recorded.
Study Population
The study population included all of the children aged 0 to 13 years enlisted in the participating practices between 1995 and 2003. No children were excluded. Over the years, the size of this dynamic cohort did not change substantially.
Outcomes
The main outcomes of interest were clinical diagnoses of acute OM (ICPC code H71) and OM with effusion (OME; ICPC code H72). A new episode of OM was recorded after an OM-free interval of ≥28 days. Other outcomes were the proportion of antibiotic prescriptions (Anatomic Therapeutic Chemical code J01) and referrals to an otorhinolaryngologist or pediatrician per 100 OM disease episodes. Because there was no direct link in the database between a disease episode and antibiotic prescription or referral, we defined a time window beginning 7 days before and ending 7 days after the OM diagnosis.
Statistical Analysis
Annual incidence rates were calculated per 1000 person-years by dividing the number of OM episodes by the total number of person-years in a specific year. Average incidence rates were also calculated for all of the years combined. To compare incidence rates across various ages, children were divided into <2, 2 to 6, and 6 to 13 years of age. Antibiotic prescription and referral rates were calculated as the number of prescriptions or referrals per 100 OM episodes registered by the GP. Nine-year differences and the corresponding 95% confidence intervals (CIs) were calculated to study the trends. χ2 tests were used to compare differences within subgroups. We used SPSS 12.0 (SPSS Inc, Chicago, IL) for all of the statistical analyses.
RESULTS
Study Population
The total number of children aged 0 to 13 years varied from 8379 in 1995 to 8512 in 2002, with an average of 8441. Gender and age distribution did not change substantially over the years: 52% of the children were male; 12% aged 0 to 2 years, 34% aged 2 to 6 years, and 54% aged 6 to 13 years.
Diagnostic Rates
The overall incidence of AOM declined from 118 episodes per 1000 person-years (95% CI: 110–125) in 1995 to 107 (95% CI: 100–114) in 2003, which is a decrease of 9% (95% CI: 8–10%; Fig 1). AOM incidence was highest in children ≤2 years of age (Fig 2A) and increased from 193 episodes per 1000 person-years (95% CI: 166–220) in 1995 to 282 (95% CI: 250–314) in 2003 (increase: 46%; 95% CI: 43–49%). Conversely, in children aged 2 to 6 years, the AOM incidence rate decreased from 179 episodes per 1000 person-years (95% CI: 164–194) in 1995 to 153 (95% CI: 138–167) in 2003 (decrease: 15%; 95% CI: 13–16%). AOM incidence decreased the most in children aged 6 to 13 years, from 60 episodes per 1000 person-years (95% CI: 52–67) in 1995 to 36 (95% CI: 30–41) in 2003 (decrease: 40%; 95% CI: 39–41%).
Overall incidences of AOM and OME in primary care (per 1000 person-years).
Incidence rate for AOM (A) and OME (B) according to age (per 1000 person-years).
Overall, AOM incidence rates were slightly higher in boys (118 episodes per 1000 person-years; 95% CI: 114–121) than in girls (105 episodes per 1000 person-years; 95% CI: 102–109; P < .001; Fig 3A). Differences in incidence between boys and girls did not change substantially over the years.
Incidence of AOM (A) and OME (B) according to gender (per 1000 person-years).
The incidence of OME declined during the 9-year period from 41 episodes per 1000 person-years (95% CI: 37–47) in 1995 to 27 (95% CI: 24–31) in 2003; a decrease of 34% (95% CI: 33–35%; Fig 1). The decline was largest in children aged 6 to 13 years, that is, from 29 episodes per 1000 person-years (95% CI: 24–34) in 1995 to 15 (95% CI: 12–19) in 2003 (decrease: 48%; 95% CI: 47–50%; Fig 2B). In children aged 2 to 6 years, the OME incidence also declined, from 64 episodes per 1000 person-years (95% CI: 55–73) in 1995 to 38 (95% CI: 31–45) in 2003 (decrease: 41%; 95% CI: 39–42%), whereas in children ≤2 years of age, the incidence increased from 29 per 1000 person-years (95% CI: 18–40) in 1995 to 48 (95% CI: 34–61) in 2003 (increase: 66%; 95% CI: 63–68%).
Overall, OME incidence rates were slightly higher in boys than in girls: 37 (95% CI: 35–39) vs 33 per 1000 person-years (95% CI: 31–34; P = .001; Fig 3B). These incidences did not change substantially over the years.
Antibiotic Prescription Rates
As expected, antibiotic prescription rates were higher in AOM than in OME (Fig 4). Antibiotic prescription for AOM rose from 44 prescriptions per 100 AOM episodes (95% CI: 40–48) in 1995 to 64 (95% CI: 59–70) in 2003, that is, an overall increase of 45% (95% CI: 42-29%). This trend was seen in all age groups, but antibiotics were most often prescribed in children aged <2 years: 81 prescriptions per 100 episodes (95% CI: 78–85) vs 43 (95% CI: 41–45) and 38 (95% CI: 35–41) in children aged 2 to 6 and 6 to 13 years, respectively (P < .001). Differences in proportions between the age groups did not change over the years. Overall antibiotic prescription rates were similar for boys and girls: 55 (95% CI: 52–57) vs 50 (95% CI: 48–53) prescriptions per 100 episodes (P = .48).
Antibiotic prescription rates for AOM and OME (per 100 episodes).
The antibiotic prescription rate for OME increased slightly from 12 prescriptions per 100 OME episodes (95% CI: 8–16) to 15 (95% CI: 10–20), an increase of 25% (95% CI: 20–30; Fig 4). Overall, antibiotics were most often prescribed in children ≤2 years of age: 21 prescriptions per 100 OME episodes (95% CI: 16–25) vs 13 (95% CI: 11–15) and 7 (95% CI: 5–9) in children aged 2 to 6 and 6 to 13 years, respectively (P = .004). These differences in proportions between the age groups remained basically the same over the years. The overall antibiotic prescription rates were similar for boys and girls, that is, 12 prescriptions (95% CI: 10–14) per 100 episodes.
Referral Rates
The overall referral rate to secondary care for AOM was similar for boys and girls and across the different age groups, that is, 3 per 100 episodes (95% CI: 2–3). Seventy percent of these referrals were to otorhinolaryngologists. During the 9-year period, referral rates for AOM did not change substantially (Fig 5).
Referral rates for AOM and OME (per 100 episodes).
The overall referral rate to secondary care for OME was 12 per 100 episodes (95% CI: 11–14), and 97% of these referrals were to otorhinolaryngologists (Fig 5). The referral rate rose slightly from 11 referrals per 100 OME episodes (95% CI: 7–14) in 1995 to 16 (95% CI: 11–21) in 2003 (increase: 45%; 95% CI: 40–51%). No differences were found between age groups and boys and girls over the years.
DISCUSSION
From 1995 to 2003, the overall GP consultation rate for both AOM and OME declined by 9% and 34%, respectively. In children aged 2 to 6 years, incidence rates declined by 15% and 41% and in children aged 6 to 13 years by 40% and 48%, respectively. In children <2 years of age, however, these rates increased by 46% and 66%. Antibiotic prescription for OM increased by 45% for AOM and by 25% for OME. The referral rate for AOM did not change over time, whereas the referral rate for OME increased by 45%.
The observed decline in consultation rates for OM is in agreement with data reported by Fleming et al6 and Otters et al,7 but inconsistent with those reported by others.4,5,17 This may be explained by differences in study designs. The studies of Lanphear et al,4 Joki-Erkkila et al,5 and Auinger et al17 were population based, whereas our study was based on patients visiting the GP. In addition, we compared data collected over a 9-year period, whereas most other studies compared OM incidence in 2 years.
The declining incidence in OM observed in our data set may be a true decline, but may also reflect a changing pattern regarding doctor consultation for OM. For example, parents may be better informed with respect to OM-like symptoms and their favorable natural course. Therefore, they may visit their GP less often. Another explanation is that GPs nowadays are more restrictive in recording clinical diagnoses of AOM and OME. However, this is unlikely, because the GPs were trained to code all visits accurately. Finally, improved diagnostic skills may have affected the incidence of OM. There is, however, no evidence that diagnostics of OM have changed over the 9 years studied.
Reasons for the contradictory results regarding incidence rates in children ≤2 years of age and those in older children are not obvious. Most likely, parents of young children with otitis-like symptoms are more inclined to consult their GP than those of older children, because they have been informed that antibiotics are most effective in the youngest age group. This would suggest that Dutch GPs adhere to the previous national guideline on AOM18 or the international guideline19 rather than to the revised Dutch guideline published in 1999.20 In this recent version, it is advised to practice initial observation in children aged ≥6 months instead of ≥2 years.
In all of the age categories we found rising antibiotic prescription rates. It might be that GPs nowadays experience greater time pressure and parental pressure to prescribe antibiotics.21 Such a trend is a reason for concern, because increased antibiotic prescription contributes to the emerging problem of antibiotic resistance and rising medical costs.9,10 The decreasing incidence rate of OME and increasing referral rate to secondary care might also reflect a changing consultation threshold: parents contact their GP later in the course of the condition when symptoms warrant referral to an otolaryngologist for hearing evaluation and/or surgical management.22,23
To appreciate the results of our study, some possible limitations should be kept in mind. First, our study was based on patients visiting their GP, which may underestimate the true incidence rates in the community. Second, misclassification because of missing data and differences in classification between years and GPs cannot be ruled out, and this may have resulted in either an overestimation or underestimation of the true incidence rates. It is, however, unlikely that this misclassification has affected the results substantially, because 90% of all patient contacts were coded. In addition, participating GPs were instructed to adhere to the guidelines of the Dutch College of General Practitioners, which not only provides guidance for management but also for the diagnosis of AOM and OME.20,22 Third, the participating GPs may not be representative of all Dutch GPs. However, main characteristics of the participating GPs were comparable with nonparticipating GPs with respect to age, gender, part-time and fulltime workers, and practice in urban and rural areas.24 The major strengths of our study are the long follow-up period, the use of multiple outcomes, and the quality of data collected by the GPs.
CONCLUSIONS
Consultation rates for OM have changed considerably over the last decade and so have antibiotic prescriptions and specialist referrals. The rising antibiotic prescription rate for OM causes concern, because it may induce increasing medical costs and antibiotic resistance.
Footnotes
- Accepted November 30, 2005.
- Address correspondence to Maroeska M. Rovers, PhD, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Stratenum 7.109, PO Box 85060, Utrecht 3508 AB, Netherlands. E-mail: m.rovers{at}umcutrecht.nl
The authors have indicated they have no financial relationships relevant to this article to disclose.
REFERENCES
- Copyright © 2006 by the American Academy of Pediatrics
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