Clinimetric Properties of the Persian Handwriting Assessment Tool as a Screening Tool for Children with Specific Learning Disorder

Background: The Persian Handwriting Assessment Tool (PHAT) evaluates speed and legibility in copying and dictation domains. The aim of the present study was to determine psychometric validation and diagnostic accuracy features of the PHAT for students with specific learning disorder. 
Methods: In this cross-sectional study, handwriting of 120 participants (typically developing students, N= 60; students with specific learning disorder, N= 60; mean age (SD): 9.23 ± 0.53 years and 9.13±0.56 years, respectively) were assessed with PHAT. Receiver Operating Characteristics (ROC) curve analysis was carried out to derive validity parameters and Area Under the Curve (AUC) for diagnostic accuracy. Discriminative validity, internal consistency, test-retest reliability and absolute reliability were examined. 
Results: The PHAT had significant ability to discriminate typically developing students from students with specific learning disorder in formation, spacing and alignment (AUC= 0.78-0.95) and moderate accuracy (AUC= 0.61-0.66) in text slant in both domains. Acceptable discriminative validity (P< 0.01), internal consistency (copying: α= 0.80-0.98; dictation: α= 0.83-0.98), and test-retest reliability (copying: ICC2,1= 0.75-0.98; dictation: ICC2,1= 0.78-0.98) were also obtained. 
Conclusion: The current study suggests that the PHAT has satisfactory reliability, validity and high to acceptable diagnostic accuracy for students with specific learning disorder.