研究背景
慢性阻塞性肺病(chronic obstructive pulmonary disease , COPD)對病患的身體功能及生活品質有很大的影響。六分鐘行走測試能有效評估患者的運動耐力，而生活品質的評估能有效反應病患的健康狀態。目前生活品質評估量表的使用非常廣泛，對COPD患者生活品質的評估不僅需要評估特定疾病的影響，還需要評估該疾病對日常生活功能和情緒的總體影響。最小重要差異值(minimal important difference, MID)係從病患角度出發，代表病人對於某療效指標感受到有意義的最小改變量，可提供明確閾值，以判斷療效是否具備實質意義。

研究目的
本研究使用2020 BMJ之 core criteria評估anchor，比較兩種anchor的結果，並使用不同生活品質量表當作anchor (Generic, disease-specific)，計算COPD病患六分鐘行走測試之最小重要差異值。

材料與方法
本研究使用National Emphysema Treatment Trial (NETT)臨床試驗提供之資料做為資料來源。研究對象為嚴重雙側肺氣腫的病人。將生活品質量表當作anchor，利用Anchor-based methods與Distribution-based methods估算六分鐘行走測試的最小重要差異值。

研究結果
以disease-specific問卷-SGRQ當作anchor估算出的六分鐘行走測試MID為25公尺；以generic問卷-SF-36當作anchor估算出的六分鐘行走測試MID為24公尺。

結論
本研究首次使用SF-36當作generic anchor估算六分鐘行走測試的最小重要差異值，研究發現使用不同anchor算出來的MID不相同，而同時使用disease-specific的生活品質量表與generic當作anchor估算的MID結果是相似的。

關鍵字
慢性阻塞性肺病、最小重要差異值、六分鐘行走測試

Background
Chronic obstructive pulmonary disease (COPD) has a destructive
impact on patients’ physical function and quality of life. Six-minute walk
test is proved to be an assessment of functional exercise capacity in
people with moderate to severe lung or heart disease. Evaluating the
quality of life can authentically reflect the health status of patients.
Minimal important difference (MID) is the smallest and meaningful
change in an outcome measure that patients perceived.

Aim of study
A. Utilize different quality of life anchor (Generic, disease-specific) to
estimate the minimal important difference for six-minute walk test in
patients with severe chronic obstructive pulmonary disease.
B. To evaluate the quality-of-life anchor, apply the core criteria of 2020
BMJ, and make a comparison between two anchors.

Methods
Our data source is National Emphysema Treatment Trial (NETT)
including patients with severe emphysema. Both anchor- and distribution-
based methods are utilized to evaluate the MID for six-minute walk test
in patients with severe COPD.

Results
There were a total of 1218 patients in the analysis and the estimated
MID for 6MWT were 25 m with SGRQ as disease-specific anchor and 24
m with SF-36 as generic anchor.

Conclusion
It is the first time to determine the MID for six-minute walk test in
patients with severe COPD by applying SF-36 as a generic anchor in this
study. The estimated MID from different type of anchors seem not much
difference in fact. It stands for that no matter generic anchor or disease-
specific anchor we chose, the determined MID for six-minute walk test
with severe COPD patients will be similar.

Key words
Chronic obstructive pulmonary disease, minimal important difference,
six-minute walk test.

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