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  • The dataset was sourced from the National Health Insurance Research Database (NHIRD) for the period from 2007 to 2009. Initiated in 1995, Taiwan’s NHI program is characterized by a single plan with the government as the sole insurer, comprehensive benefits, low co-payments, and free choice of healthcare providers from a widely-dispersed network. The NHI had 22.60 million members (an over 98% coverage rate of Taiwan’s 22.96 million residents) at the end of 2009. The NHIRD is published annually by the Taiwan National Health Research Institute, and contains the original claim data and registration files for all the enrollees under the NHI program. Many studies have used this dataset and have been published in international, peer-reviewed journals [10]. This study was exempted from full review by the Institutional Review Board (IRB) of the Taipei Medical University, after consulting with the director of the Taipei Medical University IRB, because the NHIRD consists of de-identified secondary data released to the public for research purposes. In total, 65,339 patients hospitalized with a discharge diagnosis of acute appendicitis (International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) codes 540, 540.0, 540.1 and 540.9) between January 2007 and December 2009 were selected from the NHIRD. Of these sampled patients, we identified 22,068 patients (33.8%) who had undergone laparoscopic appendectomies, according to the ICD-9-CM procedure code 47.01. The key independent variable of interest was whether the performed appendectomy was laparoscopic or open. The key dependent variables included the 30-day re-admission for the treatment of acute appendicitis, the length of stay (LOS), and the cost per discharge (defined as the aggregate monetary value of all the itemized costs of all the services and disposables billed to the NHI). We used the SAS package (version 9.1) for statistical analysis in this study. The Pearson χ2 tests were used to compare the difference between patients who had undergone laparoscopic appendectomies and patients who had undergone open appendectomies, according to the following characteristics: surgeon (age, sex, and practice location); hospital (teaching status and hospital accreditation level); and patient (age, sex and Charlson Cormobidity Index (CCI) score). Mann-Whitney tests were carried out to examine the relationship between the LOS, the cost per discharge, and the appendectomy method. The generalized estimated equation (GEE) was utilized to explore the difference in 30-day readmission rates between laparoscopic appendectomies and open appendectomies, after accounting for any clustering of the sampled patients among particular surgeons, and adjusting for surgeon, hospital, and patient characteristics. In addition, hierarchical linear regressions were performed to examine the relationship between the use of laparoscopy, the natural logarithm of the LOS, and the cost per discharge. We also calculated a propensity score for each patient and adjusted for propensity in all regression models. A propensity score was initially used to balance demographic and treatment characteristics, which were distributed unequally between patients who had undergone laparoscopic appendectomies and open appendectomies. Because the probability of undergoing laparoscopic appendectomies depends on the opinion of both the surgeon and the patient, variables for the surgeon’s age, sex, and practice location, as well as the patient’s age, sex and CCI score, were entered into a multivariable logistic regression model as predictors, to calculate the expected probability of undergoing laparoscopic appendectomies for each patient. A two-sided p value of less than, or equal to, 0.05 was considered to be statistically significant.
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