Abstract
Purpose
This study attempted to investigate the effects of a tonsillectomy on utilization of medical resources for acute respiratory infections by comparing numbers and costs of clinic visits within 1 year before and after a tonsillectomy.
Materials and methods
Data for this study were retrieved from the Taiwan Longitudinal Health Insurance Database 2005. The study includes 481 patients aged 18–80 years who underwent a tonsillectomy and 481 comparison patients. A multivariate regression model employing difference-in-difference was carried out to assess the independent association between a tonsillectomy and the number and costs of clinic visits.
Results
We found that for patients who underwent a tonsillectomy, the mean number of clinic visits for acute respiratory care 1 year before and after the index date significantly decreased from 7.3 to 4.2 ( p < 0.001). However, for the comparison group, there was no significant difference in the number ( p = 0.540) or costs ( p = 0.221) of clinic visits for acute respiratory care 1 year before and after the index date. A multivariate regression model revealed that a tonsillectomy was associated with a reduction of 3.38 in the mean number of clinic visits for acute respiratory care ( p < 0.001). In other words, a tonsillectomy reduced by 46.3% (3.38/7.3) the number of clinic visits for acute respiratory care after adjusting for sociodemographic characteristics and medical comorbidities compared to comparison patients.
Conclusions
This study demonstrated that a tonsillectomy was of substantial benefit to adult patients in that it provides decreased healthcare utilization for acute respiratory infections.
1
Introduction
A tonsillectomy is one of the most commonly surgical procedures performed on both children and adults. More than 530,000 ambulatory procedures are performed annually in children aged < 15 years in the United States . Surgical rates, however, vary considerably across countries, from 1.9 per thousand children in Canada to 11.8 in Northern Ireland in 1998 . The disparity in the frequency of tonsillectomies that exists annually worldwide may be due to a lack of consistent and sufficient evidence about the benefits of this procedure. Therefore, there is a need to determine measurable benefits of this common operation.
A number of studies have explored the potential benefits of a tonsillectomy in patients with obstructive sleep apnea , chronic rhinosinusitis , recurrent throat infection , deep neck infection , and otitis media . Evidence for the effectiveness of a tonsillectomy was shown in some studies, but the impact of a tonsillectomy is still inconclusive and is an area of debate . In addition, healthcare service utilization following a tonsillectomy has recently garnered lots of attention. Some researchers reported a decreased number of physician visits for chronic tonsillitis or respiratory infections following a tonsillectomy . However, almost all such studies only used questionnaires to explore healthcare service utilization following the tonsillectomy, and the results of survey studies may be compromised by recall bias. Furthermore, the majority of relevant studies only reported the healthcare utilization of patients who underwent a tonsillectomy alone, and almost no study has attempted to compare differences in healthcare utilization between patients who did and did not undergo a tonsillectomy. The lack of a comparison group would not allow clinicians or policy makers to understand the magnitude of the reduction in healthcare use following a tonsillectomy.
Therefore, using population-based data from Taiwan over a 2-year period, we examined the number and costs of clinic visits for acute respiratory infections before and after an adult tonsillectomy using a difference-in-difference model.
2
Methods
2.1
Database
Data for this study were retrieved from the “Longitudinal Health Insurance Database 2005” (LHID2005). The LHID2005 includes registration files and original medical claims for 1,000,000 enrollees randomly selected from all enrollees listed in the 2005 Registry of Beneficiaries under the Taiwan National Health Insurance (NHI) program ( n = 23.72 million). Numerous researchers have employed the LHID2005 to longitudinally follow-up utilization of medical services for these selected 1,000,000 enrollees and published their study results in internationally peer-reviewed journals. Therefore, the LHID2005 provides a unique opportunity to identify the relationship between a tonsillectomy and healthcare service utilization for acute respiratory infections among adults.
This study was exempt from full review by the Institutional Review Board of Taipei Medical University (TMU-JIRB 201612027) since the LHID2005 consists of de-identified secondary data released to the public for research purposes.
2.2
Study sample
This study included a study group and a comparison group. We identified and selected 569 patients who had undergone a tonsillectomy (ICD-9-CM procedure code 28.2 or 28.3) between January 1, 2002 and December 31, 2012 as the study group. We excluded 86 patients aged < 18 years and 2 patients aged > 80 years old. As a result, 481 patients who had undergone a tonsillectomy were included as the study group. We then assigned the date of receiving the tonsillectomy as the index date.
For the comparison group, we retrieved comparison patients from the remaining enrollees aged between 18 and 80 years of age in the registry of beneficiaries of the LHID2005. We further randomly selected 481 patients (one for every patient who underwent a tonsillectomy) matched with the study group by sex, age, and the year of the index date with the SAS proc. survey select program (SAS System for Windows, vers. 8.2, SAS Institute, Cary, NC). In this study, the year of the index date was the year in which the study group underwent a tonsillectomy. Comparison patients were selected by matching them to a given adult who underwent a tonsillectomy simply on their utilization of medical services in the same index year of that particular patient. Thereafter, we assigned the date of their first healthcare use occurring in the index year as the index date for the comparison group.
Ultimately, 962 sampled patients were included in this study. We then calculated the mean number and costs of clinic visits for acute respiratory infections (ICD-9-CM codes 460–466) for each patient within the 1-year period before and after their index date.
2.3
Statistical analysis
We used the SAS statistical package (SAS System for Windows, vers. 8.2) to perform the statistical analyses in this study. Paired t -tests were used to compare the difference in the mean number and costs of clinic visits within 1 year before and after the index date. Then a multiple regression employing difference-in-difference was carried out to assess the independent association between a tonsillectomy and the number and costs of clinic visits after adjusting for age, sex, geographic region, and residential urbanization level. The difference-in-difference estimate of the impact of a tonsillectomy on the number and costs of clinic visits was captured by the interaction term between a tonsillectomy and time period (before vs. after). It measures differences in the number and costs of clinic visits before and after a tonsillectomy for the study group compared to changes in the comparison group. Differences were considered significant for two-sided p values of ≤ 0.05.
2
Methods
2.1
Database
Data for this study were retrieved from the “Longitudinal Health Insurance Database 2005” (LHID2005). The LHID2005 includes registration files and original medical claims for 1,000,000 enrollees randomly selected from all enrollees listed in the 2005 Registry of Beneficiaries under the Taiwan National Health Insurance (NHI) program ( n = 23.72 million). Numerous researchers have employed the LHID2005 to longitudinally follow-up utilization of medical services for these selected 1,000,000 enrollees and published their study results in internationally peer-reviewed journals. Therefore, the LHID2005 provides a unique opportunity to identify the relationship between a tonsillectomy and healthcare service utilization for acute respiratory infections among adults.
This study was exempt from full review by the Institutional Review Board of Taipei Medical University (TMU-JIRB 201612027) since the LHID2005 consists of de-identified secondary data released to the public for research purposes.
2.2
Study sample
This study included a study group and a comparison group. We identified and selected 569 patients who had undergone a tonsillectomy (ICD-9-CM procedure code 28.2 or 28.3) between January 1, 2002 and December 31, 2012 as the study group. We excluded 86 patients aged < 18 years and 2 patients aged > 80 years old. As a result, 481 patients who had undergone a tonsillectomy were included as the study group. We then assigned the date of receiving the tonsillectomy as the index date.
For the comparison group, we retrieved comparison patients from the remaining enrollees aged between 18 and 80 years of age in the registry of beneficiaries of the LHID2005. We further randomly selected 481 patients (one for every patient who underwent a tonsillectomy) matched with the study group by sex, age, and the year of the index date with the SAS proc. survey select program (SAS System for Windows, vers. 8.2, SAS Institute, Cary, NC). In this study, the year of the index date was the year in which the study group underwent a tonsillectomy. Comparison patients were selected by matching them to a given adult who underwent a tonsillectomy simply on their utilization of medical services in the same index year of that particular patient. Thereafter, we assigned the date of their first healthcare use occurring in the index year as the index date for the comparison group.
Ultimately, 962 sampled patients were included in this study. We then calculated the mean number and costs of clinic visits for acute respiratory infections (ICD-9-CM codes 460–466) for each patient within the 1-year period before and after their index date.
2.3
Statistical analysis
We used the SAS statistical package (SAS System for Windows, vers. 8.2) to perform the statistical analyses in this study. Paired t -tests were used to compare the difference in the mean number and costs of clinic visits within 1 year before and after the index date. Then a multiple regression employing difference-in-difference was carried out to assess the independent association between a tonsillectomy and the number and costs of clinic visits after adjusting for age, sex, geographic region, and residential urbanization level. The difference-in-difference estimate of the impact of a tonsillectomy on the number and costs of clinic visits was captured by the interaction term between a tonsillectomy and time period (before vs. after). It measures differences in the number and costs of clinic visits before and after a tonsillectomy for the study group compared to changes in the comparison group. Differences were considered significant for two-sided p values of ≤ 0.05.
3
Results
For the 962-person study sample, the mean age was 39.2 (± 14.6) years, while they were 39.1 years for patients who underwent a tonsillectomy and 39.4 years for comparison patients ( p = 0.726) ( Table 1 ). After matching for sex, age, and the year of the index date, there was no significant difference in geographic region between patients who underwent a tonsillectomy and comparison patients ( p = 0.069). However, there were significant differences in urbanization level ( p = 0.001) and monthly income ( p < 0.001) between patients who underwent a tonsillectomy and comparison patients.
| Variable | Patients who underwent a tonsillectomy N = 481 | Comparison patients N = 481 | p Value | ||
|---|---|---|---|---|---|
| Total no. | Column % | Total no. | Column % | ||
| Male | 239 | 49.7 | 239 | 49.7 | > 0.999 |
| Age, mean, SD (years) | 39.1 ± 14.2 | 39.4 ± 14.9 | 0.726 | ||
| Urbanization level | 0.001 | ||||
| 1 (most) | 135 | 28.1 | 168 | 34.8 | |
| 2 | 134 | 27.9 | 135 | 28.1 | |
| 3 | 91 | 18.9 | 64 | 13.3 | |
| 4 | 65 | 13.5 | 57 | 11.9 | |
| 5 (least) | 56 | 11.6 | 57 | 11.9 | |
| Monthly income | < 0.001 | ||||
| ≤ NT$15,840 | 194 | 40.3 | 234 | 48.7 | |
| NT$15,841–25,000 | 178 | 37.0 | 128 | 26.6 | |
| ≥ NT$25,001 | 109 | 22.7 | 119 | 24.7 | |
| Geographic region | 0.069 | ||||
| Northern | 251 | 52.2 | 251 | 52.2 | |
| Central | 123 | 25.6 | 104 | 21.6 | |
| Southern | 94 | 19.5 | 114 | 23.7 | |
| Eastern | 13 | 2.7 | 12 | 2.5 | |
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