Population-based, age-specific myringotomy with tympanostomy tube insertion rates in Calgary, Canada

Population-based rates of myringotomy with tympanostomy tube insertions in Calgary from 1997 to 2000 were determined with the use of administrative databases. Age-specific rates (procedures per 1000 people per year) were 12.8, 54.2 and 11.1 for ages 0 to 11 months, 12 to 23 months and 0 to 15 years, respectively. Repeated procedures were performed on 7.1% of children <5 years of age. Acute otitis media (AOM) in children usually resolves without complications. Complications include persistent middle ear effusion that can be associated with conductive hearing loss and may lead to developmental delay. 1 For children with middle ear effusions persisting for 3 months or more with hearing loss, the main choice for surgical management is myringotomy with tympanostomy tube insertion. 2, 3 Other indications for myringotomy with tympanostomy tube insertion include frequent episodes of AOM (more than three episodes within 6 months), persistently abnormal tympanic membranes and acute complications of AOM, e.g. mastoiditis, brain abscess, facial nerve paralysis. 3, 4 Myringotomy with tympanostomy insertion is commonly performed in young children. The overall rate for children is 1.1 to 1.2% per year. 5, 6 Studies of specific age groups have reported variable rates throughout childhood with peak annual rates of 4.2 to 5.8% occurring in children from 1 to 2 years of age 7, 8 and a cumulative rate of 6.8% of all children by 3 years of age. 9 The most promising intervention to reduce the need for myringotomy with tympanostomy tube insertion in children is prevention of otitis media through vaccination. A large clinical trial of the new Streptococcus pneumoniae conjugate vaccine, Prevnar, found that tympanostomy tube placements were reduced by 20% in vaccine recipients. 10 We wished to determine the population-based rate of myringotomy with tympanostomy tube insertion procedures in our population before the introduction of S. pneumoniae conjugate vaccine. Methods. Calgary is a geographically isolated city in western Canada. The average metropolitan population from 1998 to 2000 was 913 776. The health authority that serves Calgary and the surrounding rural area [Calgary Health Region (CHR)] administers most acute health care services. Surgical procedures for children are performed in one of the acute care hospitals (inpatient or outpatient) or in a nonhospital surgical center. The latter facilities have contracts with the health authority to perform specific procedures. Individual children can have procedures performed in any or all of these facilities. With the assistance of the Corporate Data Department of the CHR, we obtained data on the total number of myringotomy with tympanostomy tube insertion procedures performed in the CHR with or without other concurrent procedures. Each procedure was counted as a single case regardless of whether unilateral or bilateral tympanostomy tubes were inserted. Cases were counted from separate administrative data sources for hospital inpatients, hospital outpatients and contracted services in nonhospital surgical centers. The International Classification of Diseases (ICD9-CM) Procedure Code 2001 (Myringotomy with Insertion Tube) was utilized for the inpatient and ambulatory cases. For the contracted services a fee code of 1001E (Myringotomy and Insertion of Drainage Tubes, Removal of Tubes) was used, which was considered equivalent to ICD9-CM Procedure Code 2001. Although the proportion of Fee Code 1001E cases that were tube removals was likely small, the inclusion of such cases would double count some children and overestimate the number of myringotomy with tympanostomy tube insertions. We addressed this issue in three steps. First we obtained data on the number of children who had two or more procedures performed during the 3-year study period in any facility (ICD9-CM 2001 in the hospital facilities or Fee Code 1001E in the nonhospital surgical facilities). For this determination we included children who were <5 years of age at the time of any procedure. Second the proportion of cases that were known repeated myringotomy with tympanostomy tube insertions (cases with ICD9-CM 2001 codes in the hospital facilities) was determined. Third the proportion of cases that were Repeated Fee Code 1001E in the nonhospital surgical facilities was determined. This proportion was the maximum overestimation of myringotomy with tympanostomy tube insertion rate and was compared with the proportion of known repeated procedures. We obtained these data for all ages for three consecutive 12-month periods, April, 1997, to March, 1998, 1999 and 2000. Data were grouped by age category, procedure and facility where the procedure was performed. Persons who did not reside in Calgary or the surrounding rural area served by the CHR were excluded. Population estimates were obtained from the province of Alberta Department of Health. Data were summarized and reported as totals and proportions. Comparisons between groups were made with the chi square test with or without odds ratios. The annual rate of myringotomies (procedures per 1000 population per year) for each age group was calculated as the total number of procedures for the 3 years divided by the total population for the 3 years for the relevant age group divided by 1000. Results. The main findings are summarized in Table 1. The peak age for myringotomy with tympanostomy tube insertion was the second year of life, followed by a large decline in the rate after 4 years of age. There were no upward or downward trends within any of the age groups during the study period.Table 1: Myringotomy with tympanostomy tube insertion procedures in the Calgary Health Region from April, 1997, to March, 2000Overall 5799 (79.7%) myringotomy with tympanostomy tube insertions were performed in hospital outpatient day-surgery facilities, 1353 (18.6%) were performed in nonhospital outpatient day-surgery facilities and 125 (1.7%) were performed in hospital inpatient facilities. There were differences in the proportions of myringotomies performed at each facility at different ages. In infants <1 year of age 84.1% of myringotomies were performed in hospital outpatient day-surgery facilities, 8.8% were performed in nonhospital outpatient day-surgery facilities and 7.1% of were performed in hospital inpatient facilities. These proportions were 82.6, 16.2 and 1.2%, respectively, from 1 to 15 years of age and 43.8, 53.5 and 2.7%, respectively, at age 16 years and older (P < 0.001 for comparisons between age groups within each facility). In the hospital outpatient day-surgery facilities and inpatient facilities, 280 repeat myringotomy with tympanostomy tube insertions were performed on 237 children before 5 years of age. Of these children 201 (84.8%) had 2 procedures, 29 (12.2%) had 3 procedures and 7 (3.0%) had 4 procedures. These procedures comprised 7.1% of the 3967 total myringotomy with tympanostomy tube insertions performed on children <5 years of age. Children who had their first myringotomy with tympanostomy tube insertion before 1 year of age were more likely to have 2 or more myringotomy with tympanostomy tube insertions during the study period than children who had their first myringotomy between 1 and 3 years of age [47 of 407 (11.5%) vs. 172 of 2390 (7.2%); odds ratio, 1.68;P = 0.003]. In the nonhospital outpatient day-surgery facilities, 83 children had 94 repeated procedures before the age of 5 years. These 94 repeated procedures (some of which would have been tympanostomy tube removals) comprised 15.3% of the 602 total procedures performed on children <5 years of age in the nonhospital outpatient day-surgery facilities and 2.0% of the total of 4658 procedures performed on all children <5 years of age in all facilities. The latter proportion is the maximum overestimation of myringotomy with tympanostomy tube insertion rates that may have occurred. Discussion. Myringotomy and tympanostomy tube placement for complicated otitis media is the most common surgical procedure performed on children in North America and Western Europe. 3 This study of population-based, age-specific rates found that majority of these procedures in Calgary were performed in children <4 years of age, with the peak rate in the second year of life. Although the rate of myringotomies drops off considerably after 4 years of age, an average of 29.6% of the total each year were performed in children from 5 to 15 years of age. Thus any new infant vaccine to prevent infections caused by otitis media pathogens should provide long lasting protection. Although the new pneumococcal conjugate vaccine reduced myringotomies by 20% in vaccine recipients, children were followed to <4 years of age by the time of publication. 10 It remains to be seen what the duration of benefit will be from this vaccine to prevent surgical treatment for otitis media. Our results for overall myringotomy rates were similar to those reported in different North American settings including the province of Ontario, 6 children enrolled in a large health insurance plan in New England, 8 children enrolled in Medicaid in Colorado 5 and children cared for in urban, suburban and rural settings in Pennsylvania. 7 Local variation in rates can occur. In Ontario, where >30 000 myringotomies are performed annually on children <20 years of age, there was a 6-fold variation in rates across 33 health regions, from 3.3 per 1000 per year to 21.3 per 1000 per year in children and young adults <20 years of age. 6 Repeated procedures were common in our study. Children who had a myringotomy with tympanostomy tube insertions before 1 year of age were somewhat more likely than older children to have two or more such procedures. This was not unexpected because it is known that onset of AOM before 1 year of age is a risk factor for recurrent episodes of AOM. 11 One of the strengths of our study is that it was population-based, which enabled us to count myringotomy with tympanostomy tube insertions performed in all settings in our community. This was important because myringotomies are increasingly performed in nonhospital surgical centers rather than in hospitals, 1 and we would have underestimated the rate of these procedures if we had merely reviewed data on hospital-based procedures. In addition we were able to show that myringotomy with tympanostomy tube insertions were more commonly performed in nonhospital surgical centers in older children and adults compared with younger children. Although we did not perform any analysis of the costs of myringotomy with tympanostomy tube insertion, our results suggest that any such studies should consider whether there are cost differences associated with the facility where the procedure is performed. Acknowledgment. We thank Blair Thomson, Analyst, Calgary Health Region Department of Corporate Data, for his efficient and expert assistance.

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