Validation

Substantial qualitative and quantitative evidence supports the validity of Neuro-QoL measures.

Have Neuro-QoL measures been validated?

This question implies a simple “yes” or “no” answer. Unfortunately, asking if a measure has been validated is not a simple question with a simple answer. A measure can never be “valid” in any unqualified sense. One might expect an expertly developed fourth grade math test to be valid for discriminating math proficiency in fourth graders. That validity, however, would not extend to discriminating math ability in high school seniors or social studies knowledge in fifth graders.

The strength of validity evidence is judged in the courtroom of scientific opinion. In fact, the judicial process provides a serviceable metaphor. Validation is the process of building a case for a measure. Psychometric studies are undertaken and their results serve as “character witnesses” that reveal the level and nature of a measure's usefulness in different populations and for different purposes

What evidence is there for the Neuro-QoL measures?

Substantial qualitative and quantitative evidence has been gathered that supports the validity of Neuro-QoL measures. Here are some highlights.

Content Validity

What Anastasi said in the context of educational testing is relevant to health measures: “content validity is built into a test from the outset through the choice of appropriate items.”1 The content validity of Neuro-QoL measures began in the use focus groups to identify health related quality of life content that most mattered to individuals with neurological conditions. Pediatric measures were developed after conducting focus groups and individual interviews.

1Anastasi A, 1988. Psychological Testing, New York, Macmillan Publishing Company, p. 122-127.

Validity Evidence in Specific Clinical Populations

A growing number of studies have collected evidence regarding the validity of using Neuro-QoL measures in particular clinical populations, including in adult epilepsy, pediatric epilepsy, multiple sclerosis, and Parkinson’s Disease. Additionally, published studies have reported results of administering Neuro-QoL to individuals with intracerebral hemorrhage, Huntington’s disease, stroke, Ehlers-Danlos syndrome, transient ischemic stroke (TIA), minor ischemic stroke, and limb loss.

Other clinical validation studies are underway and will be published in the future. These will be easily found by using the search term “Neuro-QoL” in a PubMed search.

Interpretability

An often overlooked psychometric property is interpretability. The interpretability of scores for evaluating both status and change has been addressed for Neuro-QoL measures. Conditional minimal detectable change scores have been estimated for Neuro-QoL short forms. Thresholds for severity of four Neuro-QoL measures (Fatigue, Upper Extremity Function, Lower Extremity Function - Mobility, Sleep Disturbance) have been estimated using a modified Bookmarking methodology based on the perspective of individuals with Multiple Sclerosis and clinicians.

A barrier to interpretability is the plethora of instruments that measure the same health outcome. Item response theory (IRT) approaches have been used to link scores on the physical functioning items in the Activity Measure for Post Acute Care (AM-PAC) and Neuro-QoL scores. On the PROsetta Stone® website, you will find links between scores on the PROMIS® Physical Function Measure and scores on the Neuro-QoL Lower Extremity - Mobility and Upper Extremity Function measures.

Making the case for using Neuro-QoL measures

If you are considering using a Neuro-QoL measure in a clinic or for a study, you will have substantial evidence to evaluate. The questions you ask about that evidence can also serve as the framework for supporting your choice to others (e.g., administrators, granting agency). Here are some questions to consider:

  • Why is it important to measure this construct or these constructs in my study or clinic? Describe the relevance of the symptom or outcome to the population of interest.
  • What psychometric evidence has accumulated when this measure was used in my targeted population? If you are not able to find a study in your population, weigh the evidence that exists for the measure in neurological populations with similar quality of life concerns.
  • It is appropriate to consider evidence gathered about the validity of a measure, even if a different assessment strategy was used (e.g., one short form versus another, CAT versus a short form). Keep in mind that shorter short forms sacrifice some reliability for reduction in response burden.
  • What are the alternatives to the Neuro-QoL measure(s) you selected? Clearly state why you believe a Neuro-QoL measure is a good choice, particularly for your population and for your particular purpose. Remember, validity resides in the use of the scores.

Learn More about the Psychometric Properties of the Neuro-QoL Measures

Two videos were specifically developed to explain more about the reliability and validity of the Neuro-QoL measures.

Neuro-QoL: Psychometric Properties - Reliability (4:17 min video)

Neuro-QoL: Psychometric Properties - Validity (3:53 min video)