# Translation and validation of the Thai clinical frailty scale and classification tree in older adults

## TL;DR

This study validates a Thai version of the Clinical Frailty Scale for assessing frailty in older adults, showing it is reliable and effective.

## Contribution

The study provides the first formal validation of the Clinical Frailty Scale for use in Thai populations.

## Key findings

- The Thai Clinical Frailty Scale showed strong inter-rater reliability and excellent agreement with its classification tree version.
- It demonstrated high sensitivity and moderate specificity for identifying frailty when compared to other assessment tools.

## Abstract

The Clinical Frailty Scale (CFS) is widely used for frailty assessment, but has not yet been formally validated for use in Thai populations. This study evaluated the reliability and validity of the Thai versions of the CFS (CFS-Thai) and its Classification Tree (CFS-CT-Thai).

In this cross-sectional study, 213 participants aged ≥ 65 years (127 outpatients and 86 inpatients) were enrolled from two tertiary care hospitals in Thailand. The CFS and CFS-CT were translated into Thai using standard procedures. Inter-rater reliability was evaluated in a subsample of 53 inpatients. Concurrent validity was examined using the Thai version of the FRAIL scale (T-FRAIL), the Eastern Cooperative Oncology Group Performance Status (ECOG PS), and the modified Thai Frailty Index (mTFI).

The CFS-Thai showed strong inter-rater reliability (κ = 0.80, p < 0.001) and excellent agreement with the CFS-CT-Thai (κ = 0.94, p < 0.001). It demonstrated moderate correlation with T-FRAIL (ρ = 0.53) and strong correlation with ECOG PS (ρ = 0.76) and mTFI (ρ = 0.73). Using mTFI as the reference standard, the CFS-Thai showed high sensitivity (92.7%) and lower specificity (55.0%) at cut-off ≥ 4 (AUC = 0.74, 95% CI: 0.62–0.86), while cut-off ≥ 5 improved specificity (79.3%) and retained high sensitivity (93.5%) (AUC = 0.86, 95% CI: 0.81–0.92). ECOG PS ≥ 2 provided balanced diagnostic performance (sensitivity 83.9%, specificity 93.3%, AUC = 0.89, 95% CI: 0.82–0.95).

The CFS-Thai and CFS-CT-Thai are reliable and valid instruments for frailty assessment in Thai older adults. Their diagnostic accuracy supports integration into clinical practice, especially in settings with limited geriatric expertise. Further studies should examine their implementation across diverse populations and their predictive value for clinical outcomes.