Estimating the Minimal Clinically Important Difference (MCID) of the Neuropsychiatric Inventory Questionnaire (NPI-Q) in Dementia Patients
|Keywords:||失智症;行為精神症狀;簡短版神經精神量表;信度;最小臨床重要差異值;dementia;behavioral and psychological symptoms of dementia;Neuropsychiatric Inventory Questionnaire;reliability;minimal clinically important difference||Issue Date:||2012||Abstract:||
背景與目的：失智症患者約有七成的機率會出現一種以上的行為精神症狀，且常因此造成患者生活品質下降與照護者負擔提升。近年來有許多用以評估行為精神症狀的量表，其中簡短版神經精神量表(Neuropsychiatric Inventory Questionnaire，NPI-Q)為一耗時短、評估項目完整、使用便利的評量工具，其英文版信效度已獲驗證，但尚未有針對台灣失智症患者進行之信度及最小臨床重要差異值(minimal clinically important difference, MCID)相關研究。MCID可提供臨床工作者對於量表分數改變的臨床意義，並作為臨床上失智症患者症狀追蹤及治療成效驗證之依據，故本研究欲檢驗中文版簡短版神經精神量表之信度與MCID值。
方法：本研究由台北市某失智症照護機構中收取45位失智症患者。NPI-Q將由機構中主責護理人員每個月填寫，並以李克特七點量表回報主觀認為個案症狀改善或惡化程度。另隨機抽取35位個案，於5至8天進行再測信度檢驗；施測者間信度收集24位個案，給予填答者一個月觀察時間後同時填寫NPI-Q。資料分析以組內相關係數(ICC)及加權卡帕值(weighted Kappa)計算嚴重度及困擾度二個次量表總分及各題項之再測信度與施測者間信度。MCID值以下列方式進行推算：(1)自評式整體情況量表，(2) 適宜之反應者操作特徵曲線(Receiver Operating Characteristic Curve)切點，(3)簡短版神經精神量表之標準測量誤。以此三項推估值之區間做為中文版簡短版神經精神量表於失智症患者之MCID值範圍。
Background and purpose：About seventy percent of dementia patients have at least one behavioral and psychological symptoms of dementia (BPSD). The BPSD not only can significantly aggravate caregiver’s distress, decrease quality of life of caregivers and patients but also associated with multiple medical and psychiatric needs. After review many measurements, researchers find out that the NPI-Q appears to be a valid and reliable clinical tool which is a brief, informant-based assessment of BPSD and associated caregiver stress. However, there are few studies discuss about the minimal clinically important difference (MCID) of the instruments of BPSD. Being no exception, the reliability and the MCID of the Chinese version of the NPI-Q was little revealed, which limited the interpretation of clinical change of noncognitive symptoms of dementia patients. Therefore, our objective was to establish the reliability and MCID of the NPI-Q in dementia patients.
Methods：The study included 45 dementia patients from a dementia institution at Taipei city, Taiwan. The NPI-Q was assessed by primary caregivers in dementia institutions every month from 2012.1. to 2012.6. We determinated the test-retest ability from 35 randomly selected patients within 5-8 days; inter-rater reliability from 24 patients after observation for one month by two raters. Intraclass correlation coefficient (ICC) and weighted Kappa were used to estimate the reliability of total score and each item of the NPI-Q.
The MCID of the NPI-Q were estimated by following three ways: (1) global rating of change by 7-point Liker scale; (2) optimal cutoff point by ROC curve with anchor-based method; (3) standard error of measurement (SEM) with distribution-based method. The range of these three values will become the MCID of the NPI-Q.
Result：The test-retest ability of the NPI-Q was good (the ICC of the severity and distress subscales were 0.95 and 0.96, respectively) and the inter-rater reliability was acceptable (the ICC of 2 subscales were 0.73 and 0.67, respectively). The MCID by first method for severity subscale was 3.33 point, and distress subscale was 4.15 point; by second method for severity subscale was 3.5 point, and distress subscale was 5.5 point; by last method for severity subscale was 2.77 point, and distress subscale was 3.1 point. Thus, the MCID of severity subscale of the NPI-Q was ranged from 3-4 point, for distress subscale was 4-6 point. We can claim that patients’ change have clinically important change when the difference of the NPI-Q over those range.
Conclusion: The NPI-Q showed good test-retest reliability and the acceptable inter-rater reliability. The MCID of the NPI-Q not only can assist clinicians in explaining about the clinical changes of BPSD, but also can help to determine the effects of treatment methods.
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