Development of the National Adult Reading Test-Türkiye (NART-TR) for practical assessment of mental capacity

<b>Objectives:</b> To develop the National Adult Reading Test-Türkiye (NART-TR), a reading-based mental capacity assessment tool tailored to the Turkish language. Its utility was evaluated through reliability and validity testing, with a focus on its accuracy in predicting IQ scores. <b>Methods:</b> The study sample comprised of 148 native Turkish-speaking participants, including 23 indivuduals with Extremely Low IQ (EL,FSIQ:50-69), 25 individuals with Borderline/Low Average IQ (BLA,FSIQ:70-89), and 100 healthy controls (HC) with Average/High Average/Superior IQ (AHS, FSIQ > 90). Each participant completed a sociodemographic form, the WAIS-R, the NART-TR. <b>Results:</b> The mean age of participants was 24.9 years (SD = 6.07), with 74(50%) females and 107(72.3%) holding a university degree. A large inverse correlation was observed between the total number of NART-TR errors and WAIS-R total (r = -0.75, <i>p</i> < 0.001), performance (r = -0.66, <i>p</i> < 0.001), and verbal subscale scores (r = -0.81, <i>p</i> < 0.001). Segmented regression analysis was used to estimate WAIS-R total, verbal, performance IQ scores based on NART-TR error counts. The ICCs between the estimated and actual WAIS-R total, verbal, and performance IQ scores were found to be high (0.965 [CI: 0.952, 0.975], 0.927[CI: 0.900, 0.947], and 0.833 [CI: 0.776, 0.876], respectively). Additionally, error scores could effectively distinguish between the three groups, with cutoff points of 12 for AHS-IQ vs. BLA-IQ and 20 for BLA-IQ vs. EL-IQ (Respectively, AUC = 0.988 and 0.942). <b>Conclusion:</b> The NART-TR demonstrated robust reliability and validity as a quick and efficient tool for estimating the WAIS-R scores, supporting its use in detailed cognitive research and as a practical tool for the assessment of intellectual functioning in clinical settings.