本論文旨在探討市場競爭對於自付差額之醫材利用與醫療品質的影響，並利用2007至2017年間接受經皮冠裝動脈介入性治療並植入支架的病患為研究標的進行研究。本文首先以市場競爭和醫師偏好為解釋變數，探討病患治療中是否選擇利用塗藥支架；接著以市場競爭與使用支架類型為解釋變數，觀察病患的醫療成效，並評估對醫療品質的影響；最後，利用結構方程模型進行中介分析，以使用塗藥支架為中介因子、市場競爭為重要解釋變數，評估競爭對於醫療品質的直接效果及透過塗藥支架產生的間接效果，以探討市場品質的提升主要來源。

根據實證結果，本研究發現市場競爭和醫師偏好皆與塗藥支架的利用呈現正相關，且醫師偏好的影響高於其他解釋變數。此外，本文也發現市場競爭的確會造成醫療成效的提升，顯示市場存在品質競爭的現象，且同時競爭也帶動提升塗藥支架的利用率，與醫療競武現象相符。然而，從中介分析中可知，在中度集中市場上，品質提升主要是來自間接效果(利用塗藥支架)的推動。

綜上所述，儘管競爭確實帶來醫療品質的提升，但同時也會為市場帶來醫材利用的改變和醫療競武現象，將有可能對於社會弱勢者產生不利的影響。然而，本研究仍存在一些限制，希冀未來研究能使用更完善的研究方法，深入了解醫療市場競爭對於醫材利用與醫療品質的影響。

This research explores the impact of market competition on the utilization of out-of-pocket medical devices and quality of care. This study focuses on patients who received percutaneous coronary intervention (PCI) and had at least one coronary stent inserted from 2007 to 2017. Firstly, this research examines the influence of market competition and physicians’ preference on whether patients will use drug-eluting stents (DES) in therapy. Subsequently, using market competition in healthcare as an explanatory variable, this study observes its impact on patients’ medical outcomes, which can be regarded as a proxy variable for the quality of care. Lastly, the mediation analysis in the structural equation model will be used to evaluate the composition of the impact of market competition on quality of care, including the direct and indirect effects mediated through DES usage, thereby exploring the primary source of quality improvement in the market.

Based on the empirical results, this study finds a positive correlation between market competition, physicians’ preference, and the utilization of DES, with physicians’ preference exerting a stronger influence than other explanatory variables. Additionally, the model shows that the market competition will contribute to a better quality of care, indicating the presence of quality competition in the recent market and increasing the usage of DES, aligning with the phenomenon of the medical arms race (MAR). However, the mediation analysis shows that the indirect effect drives quality enhancement in a moderately competitive market via DES utilization.

As discussed above, although market competition can enhance the quality of care, it also brings out the changes in the utilization of medical devices and the phenomenon of MAR simultaneously, which might not benefit vulnerable groups. Whereas, there are still some limitations in this research, and future studies are encouraged to adopt more sophisticated methods and models for a deeper understanding of the effects of healthcare market competition on the utilization of out-of-pocket payment medical devices and quality of care.

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