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Coronary Angiography Utilization and Costs for Coronary Artery Bypass Graft Surgery Patients in Turkey

Introduction To assess excess use of coronary angiography prior to coronary artery bypass graft surgery and its association with mortality, health care costs, and hospital quality in Turkey. Methods Using Turkish National Health Insurance Data (2009–2011) that included patients who underwent cardiac surgery, coronary angiography utilization was identified. Propensity score matching was used to compare survival rates and annual health care costs of patients in a coronary angiography excess-use group (>1 angiogram) and in a standard-therapy group (1 angiogram). The empirical Bayesian approach was used to combine mortality and hospital volume for quality index. The relationship between hospital quality and excess use of coronary angiography was assessed using Chi-squared tests. Results Out of 20,126 patients identified, 7.27% of patients underwent excessive coronary angiography procedures (excess-use group), with an average annual cost at 9.7% higher than those who had a single angiography (standard-therapy group; P < 0.01). Operational mortality associated with excessive use was significantly higher as well (7.4% versus 5.4%, P < 0.02). There exists variation in the use of coronary angiography across cities and hospitals. Patients who underwent cardiac surgery in high-quality hospitals were less likely to have excessive angiography use than those in low-quality hospitals (7.0% versus 9.5%, P < 0.01). Conclusion In Turkey, excess use of coronary angiography prior to coronary artery bypass graft surgery is associated with higher operational mortality, higher expenditures, and lower hospital quality.


INTRODUCTION
Coronary artery bypass graft (CABG) surgery is one of the most common surgical procedures performed to relieve angina symptoms in patients with coronary artery disease [1,2].
The surgery improves the quality of life and survival rates of patients with coronary artery disease [3][4][5].
Coronary angiography is considered the standard procedure for CABG assessment [6].
Every year, millions of patients get an angiogram, wherein a long, thin, flexible tube called a catheter is inserted in the arm or groin, and threaded to the heart to check for blocked arteries that may lead to a heart attack. Dye is injected through the tube to make blockages visible on X-rays [7]. Although angiographies are effective in select populations, the overall appropriateness of their use is questioned [8][9][10]. The test carries a small (\1%), but serious, risk of causing a stroke or heart attack, and also entails radiation exposure [11].
The troubling association between the increased number of CABG surgeries and high frequency of costly angiograms to check for heart disease has caused payers to request studies to outline the benefits, risks, and outcomes of these procedures. The cost of these procedures will be major contributors to increased health care spending [12]. Prior studies have indicated that excess use of and increased costs associated with these procedures are related to variation in the quality of care [13].
This study aimed to demonstrate the variation in the use of coronary angiography for patients who underwent CABG surgery in Turkey using nationwide, real-world data. The difference in mortality rates and annual health care costs associated with coronary angiography overuse was calculated. The correlation between the number of angiographies and hospital quality based on a previously validated claimsbased quality index was estimated. This article does not contain any studies with human or animal subjects performed by any of the authors.

Statistical Analysis
Paired t tests and Chi-square tests were used to compare the demographic, clinical, and provider characteristics between the two groups: standard-therapy group and excess-use group. To estimate risk-adjusted differences in mortality and annual health care costs with the overuse of angiography, the propensity score matching (PSM) method was used. This technique, employed by the predicted probability of group membership, isolates the observed bias from the estimation [16].
Following previously published guidelines for choosing the most appropriate matching technique for the present data, one-to-one matching with caliber was used [17]. Caliber was selected as 25% of the standard errors of the estimated propensity score. Using regression analysis, mortality rates and total health care costs for patients with standard therapy and excess use were also estimated. In particular, Cox regression was used for operational mortality estimation, and generalized linear models were used for total health care cost estimation for both groups.
Hospital quality was characterized by a previously validated composite score, which combines operational mortality with hospital volume information using Bayesian techniques [18]. Hospital procedure volume was assessed as the total number of procedures performed by index is presented in quartiles to rank low-to high-quality hospitals. Since this index combines information from multiple quality domains into a single measure, it has been referred to as the ''gold standard'' for hospital performance comparisons on US national standards of safety, quality, and efficiency that are most relevant to patients and payers [19][20][21].
All statistical analyses were conducted using SAS Ò V.9.3 (SAS Institute Inc., North Carolina, USA) and STATA Ò V11 (StataCorp LP, Texas, USA). In particular, SAS V.9.3 is used for data management, and STATA V11 is used for statistical analysis.

RESULTS
A total of 20,126 patients satisfied all inclusion criteria, of which, 88.12% (n = 17,734) underwent CABG surgery after one coronary angiography (standard-therapy group), and 7.27% (n = 1,464) had more than one coronary angiography (excess-use group) within 3 months prior to CABG surgery. The distribution of excess use is presented in Fig. 1.
Few CABG surgery patients (4.61%) did not utilize coronary angiography prior to surgery.
Less than 1% of these patients were admitted into the emergency care settings. The majority of surgeries were performed in high-volume hospitals (58.75%), and 11.16% of the surgeries occurred in teaching hospitals (Table 1).

Geographic variation in coronary
angiography use is presented in Fig. 2. To increase the reliability of the estimate, cities with\20 angiography procedures were not taken into consideration in the rates. The proportion of CABG surgery patients with excess use was the highest in Erzurum (13.36%), followed by Batman (12.28%), and Antalya (11.95%).
Thirty-six out of 81 cities did not have centers for coronary angiography, and 1,288 patients underwent CABG surgery without having a coronary angiography. A total of 33.17%   Fig. 4). For the complete overview of the study population, patients who did not receive the angiography were also compared with the main study groups. After applying risk adjustment, standard-therapy patients use had lower mortality rates (3.96% versus 6.01%, P\0.010) and incurred lower annual health care costs (€7,850 versus €8,081, P\0.010) relative to patients who did not have angiography. Patients with excess use of angiography incurred higher annual health care costs (€8,695 versus €8,148, P\0.010) and had no significant operational mortality rate advantage (5.74% versus 6.09%, P = 0.675), relative to patients without angiography use.
In this study, angiography utilization in a disease-specific (CABG surgery) cohort of patients with uniform insurance coverage in Turkey was examined. Results determined that after adjusting for demographic and clinical factors, there was significant variation in coronary angiography use. Regional practice patterns emerged, showing that more procedures were performed in cities such as Erzurum, Batman and Antalya, relative to the rest of Turkey.
Current guidelines for patients undergoing assessment for obstructive coronary artery disease are designed to limit the number of invasive angiographies and thereby enhance the diagnostic yield of cardiac catheterization [26]. However, a substantial increase in these procedures has contributed to a rise in medical costs. Several factors are responsible for this increase, including wider availability of technology, increased demand by patients and physicians, and favorable reimbursements [27].  significantly [28]. Therefore, the rise in procedure utilization is expected. However, the association with excess use and hospital quality is of particular interest. Often, coronary  costs for the excess-use group were 9.7% higher than for standard-therapy group.
Mortality rates were 1.37 times higher.
Hospital quality was assessed using a previously validated composite score, which has been applied by a large group of coalitions in the United States [19,21]. Traditional quality indicators, whether they are based on structure, process, or direct outcomes measures, have significant limitations. For example, hospital volume is important for high-risk procedures but does not reliably predict performance for individual hospitals. Process measures often fail to explain observed variations in hospital mortality rates. Direct outcomes measures, because of sample size limitations, are often imprecisely estimated and do not produce a reliable estimate of hospital performance. The composite measure used in this study has the potential to obviate these limitations, because it combines information from surgical volume and operational mortality into a single summary measure. This study presents a negative relationship between high-quality hospitals and excess use of coronary angiography.
Numerous studies have been done to evaluate factors that may influence the results of a variety of surgical procedures. Almost invariably, when assessed, surgeon experience is an important factor in determining the likelihood of successful outcomes from surgery. For example, in shoulder replacement procedures, a surgeon who performs 30 replacements over 6 years is considered ''high volume'' [29]. These doctors had lower complication rates and their patients had shorter hospital stays than ''low volume'' surgeons. In hip replacement surgery, surgeons who performed fewer than 30 hip replacements each year had more patients requiring revision surgery [30]. In another study, 5 years of scoliosis surgery experience did not improve outcomes [31]. Therefore, it is difficult to define a specific number of procedures that deem a surgeon proficient. In the present study, the authors empirically determined the effect of the volume of procedures by including them in the hospital quality index.
The present study has several strengths. To the authors' knowledge, this is the first study in Turkey that includes a large, diverse, and geographically varied sample of patients who received coronary angiography before CABG surgery. It is also the first study that shows the relationship between hospital quality and the excess use of coronary angiography. Excess costs associated with angiography overuse and operational mortality are also presented for the first time in Turkey.
Data were limited in their clinical information related to disease severity in coronary angiography patients. The Elixhauser Index and admission acuity were used in the attempt to control for differences. These measures are not representative of disease severity; therefore, the impact of severity on coronary angiography excess use may be underestimated. Although claims data are extremely valuable in revealing the real-world practice of procedures and determining   [33].
Regression analysis uses the outcome as a lefthand-side variable, which is not supposed to be available during randomization. Second, confounding by treatment variables is often the main challenge to validity, and the propensity score focuses directly on treatment variables [34]. Third, a matched analysis can eliminate noncomparable exposed subjects [35]. Finally, PSM provides robust estimates when there are relatively few outcomes to compare with the number of potentially few outcomes [36][37][38]. Proponents of regression analysis, however, focus on statistical advances in regression literature [39,40] Table 4.