Substance use disorder symptoms: Evidence of differential item functioning by age

Kendon J. Conrad*, Michael L. Dennis, Nikolaus Bezruczko, Rodney R. Funk, Barth B. Riley

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

23 Scopus citations


This study examined the applicability of substance abuse diagnostic criteria for adolescents, young adults, and adults using the Global Appraisal of Individual Need's Substance Problems Scale (SPS) from 7,408 clients. Rasch analysis was used to: 1) evaluate whether the SPS operationalized a single reliable dimension, and 2) examine the extent to which the severity of each symptom and the overall test functioned the same or differently by age. Rasch analysis indicated that the SPS was unidimensional with a person reliability of .84. Eight symptoms were significantly different between adolescents and adults. Young adult calibrations tended to fall between adolescents and adults. Differential test functioning was clinically negligible for adolescents but resulted in about 7% more adults being classified as high need. These findings have theoretical implications for screening and treatment of adolescents vs. adults. SPS can be used across age groups though age-specific calibrations enable greater precision of measurement.

Original languageEnglish (US)
Pages (from-to)373-387
Number of pages15
JournalJournal of applied measurement
Issue number4
StatePublished - 2007
Externally publishedYes

ASJC Scopus subject areas

  • Medicine(all)


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