Quality of life and its measurement: important principles and guidelines.

Nevin et al. (2005) wrote a how-to guide for picking quality-of-life tools for people with intellectual disability.

They listed six questions—who, what, when, where, why, how—to ask about any scale before you use it.

No new data were collected; the paper is a narrative review of measurement rules.

The authors found that most QOL tools skip at least one of the six questions.

They warn that a tool missing even one question can give misleading scores for clients with ID.

Schalock (2004) came first and mapped what we still do not know about QOL; Nevin et al. (2005) turned those gaps into a checklist you can use Monday morning.

Hatton et al. (2005) then tested the checklist idea across four countries and showed the same domains work in different cultures, backing the "where" and "who" questions.

Balboni et al. (2013) and Simões et al. (2015) ran head-to-head studies on self vs proxy report and on two different scales; both found the choice of tool changes the score—exactly what the six-question screen predicts.

Pickard et al. (2022) and Fujiura (2012) push the other way, showing adults with ID can give valid self-reports if you adapt the wording; this looks like a clash, but it fits the "how" question—adapt when the client can respond, use proxy when they cannot.

Before you add any QOL scale to an ISP, run it through the six questions. If the manual does not say who it was normed on or how items were simplified, keep looking. This five-minute habit saves months of bad data and keeps staff, families, and funders on the same page about what "quality of life" really means for your client.