Test–retest reliability and convergent validity of the test of nonverbal intelligence-fourth edition in patients with schizophrenia

BACKGROUND: Fluid intelligence deficits affect executive functioning and social behaviors in patients with schizophrenia. To help clinicians manage fluid intelligence deficits, a psychometrically sound measure is needed. The purposes of this study were to examine the test–retest reliability and convergent validity of the Test of Nonverbal Intelligence-Fourth Edition (TONI-4) assessing fluid intelligence in patients with schizophrenia. METHODS: A total of 103 patients with stable condition were assessed with the TONI-4 twice with a 4-week interval to examine the test–retest reliability. We further used the Montreal Cognitive Assessment (MoCA) and the Tablet-Based Symbol Digit Modalities Test (T-SDMT) to examine the convergent validity of the TONI-4. RESULTS: The intra-class correlation coefficient was 0.73 for the TONI-4. The percentages of standard error of measurement and minimal detectable change for the TONI-4 were 5.1 and 14.2%, respectively. The practice effect of the TONI-4 was small (Cohen’s d = − 0.03). Convergent validity showed small to moderate significant correlations between the TONI-4 and the MoCA as well as the T-SDMT (r = 0.35, p = .011 with the T-SDMT and r = 0.61, p < .001 with the MoCA). The results demonstrated that the TONI-4 had good test–retest reliability, limited random measurement error, and a trivial practice effect. The convergent validity of the TONI-4 was good. CONCLUSIONS: These findings indicate that the TONI-4 has potential to be a reliable and valid assessment of fluid intelligence in patients with schizophrenia.