口腔保健関連 QOL の短形式尺度の開発

Developing short-form measures of oral health-related quality of life.

抄録

目的:

項目インパクト法を用いて，良好な心理測定特性とフロア効果を有する口腔健康影響評価表（OHIP）の短形式を開発した．

OBJECTIVES: Using the item-impact method, we developed an alternative short-form Oral Health Impact Profile (OHIP) that has good psychometric properties and minimal floor effects.

方法:

OHIPのデータは、高齢のカナダ人サンプルから2つの時点で収集された。1回目の測定で得られたデータを用いて14項目の短形式を作成し、2回目の測定で得られたデータを用いてSlade（1997）が開発したオリジナルの短形式と対照回帰法により後者の心理学的特性を比較した。

METHODS: OHIP data were collected from a sample of older Canadians at two points in time. Data from the first administration were used to develop a 14-item short-form measure; data from the second compare the latter's psychometric properties with those of the original short form developed by Slade (1997), who used a controlled regression procedure.

結果:

項目インパクト法に基づく短形式は、回帰アプローチに基づく短形式と共通する項目が2つしかなく、より高頻度の項目を含んでいた。回帰法の短形式は顕著な床効果を示したが、インパクト法の短形式は49項目のOHIPと同程度の床効果を示した。前者は歯列矯正者と無歯顎者を識別したが、後者は識別しなかった。両者とも，義歯の有無，ドライマウスの有無，咀嚼障害の有無を弁別した．また，両者は，口腔保健の自己評価，口腔保健の満足度，歯科治療の必要性の自己認識とも有意に関連した．相関の強さは回帰短答式でやや強く，識別的な尺度として優れていることが示唆された．しかし，フロア効果により，インパクト短形式よりも変化に対する感度が著しく低かった．口腔保健関連QOL尺度を短縮する項目インパクト法は、統計的手法よりもサンプル間でより安定した結果をもたらすことが示唆された。

RESULTS: The short form based on the item-impact method had only two items in common with the short form derived from the regression approach and contained more high-prevalence items. The regression short form was subject to marked floor effects, while the impact short form had floor effects comparable to those of the full 49-item OHIP. The former discriminated between dentate and edentulous subjects, while the latter did not. Both discriminated between dentate subjects who did and did not wear dentures, those with and without dry mouth, and those with and without chewing problems. Both were also significantly associated with self-ratings of oral health, satisfaction with oral health, and self-perceived need for dental treatment. The strength of the associations was somewhat stronger with the regression short form, indicating that it performed better as a discriminatory instrument. However, because of its floor effects, it was markedly less sensitive to change than the impact short form. There was an indication that item-impact methods of shortening oral health-related quality of life measures produced more stable results across samples than the statistical approach.

結論:

短形式尺度の内容の妥当性は常に損なわれているため，異なる目的や異なる患者集団には，異なる短形式が必要とされる．Slade (1997)が開発した回帰短答式は、識別を目的とする場合に適していると思われるが、集団の口腔保健関連QOLの記述や変化の検出を目的とする場合には、ここで開発した影響短答式が望ましいと思われる。

CONCLUSIONS: Because the content validity of short-form measures is always compromised, different short forms are required for different purposes and different patient populations. The regression short form developed by Slade (1997) is likely to be better when the aim is to discriminate, while the impact short form developed here may be preferable when the aim is to describe the oral health-related quality of life of populations or to detect change.