Objective: This study aimed to test the validity and reliability of a modified Yale Preoperative Anxiety Scale (m-YPAS) in the Thai language, and to find out whether a short version of the m-YPAS correlated with the full version.
Material and Method: After using the standard forward-back-forward translation technique to convert the original m-YPAS to a Thai m-YPAS-full version, the content validity was approved. The children’s behavior in the waiting area and induction phase was video recorded. The inter- and intra-rater reliabilities were tested by two residents and two nurses, who independently scored a random arrangement of 40 videos. Then, the construct and concurrent validities were examined.
Results: The content and construct validity was acceptable to good. The inter-rate reliabilities, intraclass correlation coefficients ranged from 0.75, 95% CI 0.63 to 0.84 in activity and use of parents category to 0.88, 95% CI 0.80 to 0.93 in emotional expressivity category. The intra-rate reliabilities, ICC ranged from 0.88, 95% CI 0.72 to 0.93 to 0.97, 95% CI 0.94 to 0.98 for R1, and from 0.78, 95% CI 0.63 to 0.88 to 0.94, 95% CI 0.89 to 0.97 for R2. The Cronbach’s alphas of the full and short versions of the m-YPAS-Th were 0.98 and 0.97, respectively. The concurrent validity between the full and the short versions of the Thai m-YPAS had a very strong, positive correlation, which was statistically significant (rs = 0.98, p = 0.01).
Conclusion: The modified Yale Preoperative Anxiety Scale in the Thai language was excellent in terms of both reliability and validity, and it correlated with the short version of the m-YPAS.

Keywords: Anxiety scale, Young children, mYPAS, Short version, Thai