The localization and improvement of the Functional Status Scale and the reliability and validity in very low birth weight infants.

Objective: To develop a Chinese version of Functional Status Scale (FSS) and to test its reliability and validity in very low birth weight infants (VLBWIs).

Methods: The FSS was translated into Chinese and the content was modified in accordance with relevant guidelines and specifications. The Chinese version of FSS was applied to evaluate VLBWIs admitted from January 2018 to June 2020 at 7th day after birth and 34 weeks of postmenstrual age, respectively. The scores were analyzed by descriptive statistics (coefficient of variation method, critical ratio method and answer distribution analysis method), and the reliability and the validity were analyzed. The internal consistency reliability was analyzed using Cronbach's α coefficient, the inter rater reliability was analyzed using Spearman correlation coefficient. The content validity was analyzed using correlation coefficient method and expert scoring method; the structural validity was analyzed using exploratory and confirmatory factor analysis method; the known group validity was analyzed using area under the curve (AUC) value and Pearson correlation coefficient. The preliminary response of the initial and re-evaluation scales was calculated.

Results: After screening by inclusion and exclusion criteria, 548 and 523 VLBWIs were included for initial evaluation and re-evaluation, respectively. Descriptive statistics showed that the mean was close to the median, the maximum and minimum values were close to or equal to the values at both ends, and the coefficient of variation was >0.15. The critical ratio method showed that the | | value of all items in the initial evaluation and re-evaluation was >3 ( <0.01). The answer distribution analysis method showed that the answer selection rate of different levels of each item was <80%. Internal consistency test showed that the general Cronbach's α was 0.803 and the re-evaluation Cronbach's α was 0.708, with a good internal consistency. According to the inter-rater reliability, the Spearman correlation coefficient was 0.968 in the initial evaluation and 0.989 in the re-evaluation ( <0.01). The correlation coefficient of the items in the scale by the correlation coefficient method was more than 0.4. The item-level content validity index (I-CVI) was greater than 0.78, universal agreement of scale of content validity index was 0.83, the average of scale of content validity index was 0.97 and the Kappa was greater than 0.74. Exploratory factor analysis showed that the initial Kaiser-Meyer-Olkin (KMO) value was 0.846, the re-evaluated KMO value was 0.843 ( <0.01). There was one factor with extracted eigenvalue>1, which could explain 54.221% and 53.403% of the total variation respectively, suggesting that there was a common factor in the initial evaluation and re-evaluation scales, which was consistent with the original scale design. Confirmatory factor analysis showed that the items in the initial and re-evaluation were significant ( <0.01), and the value of standard load coefficient was greater than 0.5. The known group validity showed that FSS had a good predictive and discriminative ability for short-term outcomes. The items of mental status, motor function, sensory and communication in the re-evaluation scale had a good correlation with gross motor and fine motor energy areas in Gesell developmental schedule. The Pearson correlation coefficient between initial evaluation and re-evaluation was 0.609 ( <0.01).

Conclusion: The Chinese version FSS scale has good reliability and validity, the included items are simple and easy to be applied in clinical practice.