Growth Scale Values Are Gaining Traction in Clinical Trials
Growth scale values (GSVs) have gained traction as a more precise option for measuring outcomes in clinical trials.
Unlike raw scores and age equivalents, which lack precision to quantitatively measure developmental change, GSVs have distinct advantages for measuring change over time. This is a key reason that J. Lynsey Psimas, PhD, director of business development at Pearson Clinical Assessments, believes the scores have become increasingly popular in research.
“GSVs offer a continuous, interval-based score that is sensitive to small but meaningful changes, making them particularly valuable for assessing treatment effects and individual patient progress,” Psimas says.
GSVs aren’t new. The scores have been used for more than 50 years and are a scoring option for several popular clinical outcome assessments, including the Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-4) and the Vineland-3.
What are Growth Scale Values?
GSVs are a type of score that represent absolute performance on a test. They are a linear transformation of a raw score, designed to measure individual change over time, unlike normative scores which compare performance to same-aged peers.
The scores can be developed for nearly all scales with sufficient data and are especially effective for more precisely measuring change in pediatric neurodegenerative disease. GSVs are often used in tandem with raw scores in research.
“GSVs provide an additional scoring option to increase precision when a very sensitive score is required to ensure even the slightest growth or regression is clear in the research,” Psimas explains.
There are a few guidelines for using GSVs to measure changes in performance:
- GSVs obtained on the same subtest can be compared across administrations and can be subtracted or averaged to monitor progress.
- GSVs should not be compared across different subtests.
- Use caution when interpreting scores when testing intervals are less than three months apart because practice effects could inflate growth rates.
- Interpreting fewer than three GSVs might not form a reliable growth trend.
How GSVs Measure Up
GSVs are just one of the scores that can be used in clinical trials. Similar to raw scores and age-equivalent scores, GSVs reflect raw performance, but there are several distinct advantages to using GSVs over other tools. In particular, they allow you to look at change over time on an interval-based scale; it’s an important metric for understanding the impact of treatment.
Among other qualities, GSVs offer the distinct advantage of improving precision in data analysis. There are also other benefits to using GSVs:
- GSVs can be used for out-of-level testing.
- GSVs offer increased precision over raw scores due to equal-interval scaling.
- GSVs are sensitive to change over time.
- GSVs indicate the magnitude and direction of change in a patient.
In the rare-disease space, the equal-interval scaling feature of GSV scores increases confidence that calculated differences truly represent change in ability. These advantages are just one reason that GSVs have been called a “superior method of measuring change over time” and that researchers urge their inclusion in rare-disease outcome studies.
“By incorporating GSVs into study designs, researchers can enhance the precision and interpretability of their findings,” Psimas says. “It ultimately contributes to more reliable outcomes in clinical research.”
Download our infographic to learn more about the facts, benefits, and advantages of implementing Growth Scale Values (GSVs)
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