Measurement Equivalence of the K6 Scale

Abstract

This study examined the measurement equivalence of the K6 across diverse racial/ethnic and linguistic groups in the U.S. differential item functioning analyses using item response theory were conducted among 44,846 U.S. adults drawn from the California Health Interview Survey. Results show that four items (“nervous,” “restless,” “depressed,” and “everything an effort”) varied significantly across races/ethnicities and four items (“nervous,” “hopeless,” “restless,” and “depressed”) varied significantly across languages. In additional effect size analyses designed to separate effects of race/ethnicity from language, the structure of the White English group was substantially different from both the Hispanic/Latino English group and Hispanic/Latino Spanish group, whereas the Hispanic/Latino Spanish group was not different from the Hispanic/Latino English group. The findings suggest that there was evident measurement nonequivalence in the K6 among racially/ethnically and linguistically diverse adults and that the observed nonequivalence in the K6 appears to be driven by language rather than race/ethnicity.

Measurement equivalence of English versus native language versions of the Kessler 6 (K6) Scale: An examination in three Asian American groups.

“…Although a few studies examined measurement equivalence of an instrument between English-using and Spanish-using Hispanics (e.g., Azocar et al, 2001 ; Hahn et al, 2014 ; Kim et al, 2016 ; Jones, 2006 ), Asian Americans have received little attention mostly due to the lack of data that include sufficient number of participants interviewed/surveyed in Asian languages. The Asian American Quality of Life (AAQoL) survey, which employed multiple strategies to capture cultural and linguistic diversities of Asian Americans (e.g., use of Asian language versions of the questionnaire, bilingual and bicultural research personnel, and community partnerships), included many non-English speaking participants, offering an optimal opportunity to explore measurement equivalence between English and non-English (Chinese, Korean, and Vietnamese) versions of the same instrument.…”

“…For example, Hahn and colleagues (2014) confirmed the absence of DIF by survey language in their development of linguistically equivalent English and Spanish measures of social health. On the other hand, studies focusing on affective and cognitive measures report the presence of DIF between English and Spanish versions of an instrument (e.g., Azocar, Arean, Miranda, & Muñoz, 2001 ; Kim, DeCoster, Bryant, & Ford, 2016 ; Jones, 2006 ), elucidating potential reporting bias that may stem from linguistic differences in nuances and connotations.…”

“…However, these studies combined data from participants who were interviewed in English and in their native language, thus leaving open the possibility that the interview language could cause measurement bias. Substantiating this possibility, a recent study found that the measurement structure of the K6 in the CHIS participants who were interviewed in English was different from those interviewed in Spanish ( Kim et al, 2016 ). Analyses showed that the structure of the non-Hispanic White group was different from that of Hispanics who were interviewed in either Spanish or English, but there was no difference between the two language versions for Hispanics.…”

“…Using an Asian American sample collected via methodological strategies designed to capture cultural and linguistic diversities, the goal of the present study was to assess the measurement equivalence of the K6 based on the selected survey language (English or one’s native language). Based on previous studies on language-based equivalence in affective and cognitive measures (e.g., Azocar et al, 2001 ; Kim et al, 2016 ; Jones, 2006 ), we hypothesized that DIF would exist between English and Asian language versions of the K6.…”

Distribution of psychological distress is stable in recent decades and follows an exponential pattern in the US population

“…Researchers have developed standardized scales, such as the six-item Kessler psychological scale (K6), for the assessment of psychological distress 2 . Previous clinical research has demonstrated that the K6 has a sensitivity of 0.34 and specificity of 0.96 at a cut-point 13 to identify psychological distress associated with common mental illness 3 , although several studies have reported inconsistent findings on the psychometric properties of the K6 among different general populations 4,5 .…”