This cross-cultural validation study was conducted from January 2020 to January 2021 after the approval from Riphah International University and after the approval of the original author of CAIT. The study was started after the approval of the ethical committee from Riphah International University with a reference number REC/RCRS/20/1019.
Tool Description (CAIT)
The CAIT consists of 9-items, with a total score of 30-points, for measuring the severity of functional ankle instability. A cut-off value of 27.5 was calculated by Hiller et al., (2006) to indicate ankle instability . This means that all scores that are equal or less than 27 were considered unstable and the range above it was considered stable.
A standardized translation method was used according to international guidelines (Beaton), followed in previous studies . Validity and reliability were measured according to COSMIN guidelines . All steps are shown in Fig. 1.
Step 1: Forward Translation
CAIT was translated into Urdu by two bilingual translators (native) one was an informed (medical, a senior physical therapist) and the other was an uninformed (non-medical, expert in both languages English and Urdu) translator.
Step 2: Experts Review Committee
Urdu was drafted after the consensus of the expert committee by modifying the required words to maintain the original concept of the questions (three experts who have experience of more than 10 years in rehabilitation were involved in the expert committee).
Step 3: Back Translation
Urdu CAIT was translated back into English by two independent bilingual translators. Back translation was drafted by the consensus of the expert committee.
Step 4: Experts Review Committee
The final version of the back translation was drafted after the experts’ review and sent to the original author for any further change. The percent agreement of three experts was noted in the whole process of translation shown in Table 1.
Step 5: Final Urdu Version
The final Urdu version was drafted after removing all the discrepancies. Content validity Index (CVI) and a pilot study were done.
Content Validity Index of pre-final version
The content validity of the pre-final Urdu version was determined by the clinical physical therapists (seven physical therapists were involved in this process). None of them were involved in the translation process. Content validity was determined; relevance, clarity, ambiguity, and simplicity, four subparts were further evaluated on the Likert scale, Waltz and Bausell method was adopted [19,20,21]. The content validity of instruments is also measured by several CVI. In this study, we have used 4 points ordinal content validity index developed by Waltz  to measure the content validity of Urdu CAIT. It has four categories: relevance, clarity, simplicity, and ambiguity and each of the categories of the CVI has been arranged on four points Likert scale.
A pilot study was done on 10 chronic ankle instability patients and healthy controls with no ankle instability. Discriminant validity was determined by comparing 10 patients with 10 healthy controls. The final version was drafted after application on the pilot data.
Participants and data collection
Participants for the main study were recruited from patients having ankle problems analyzed as ankle instability and were treated by physiotherapists at different private athletic training institutes and hospitals of Multan (Multan Medical and Dental College, Nishter Hospital, Multan), Pakistan. A Convenience sampling technique was used.
Inclusion criteria for participants were: aged 20–50 years, able to understand and read the Urdu language, and suffering from ankle instability. For patients with complaints of turning of the ankle especially on uneven surfaces or in sports repeatedly, pain, swelling, tenderness, and persistent discomfort were included.
Exclusion criteria were: history of ankle surgeries, systemic and secondary ankle problems, central or neurological signs like paraesthesia or numbness, any red flags like night sweating, tumors or oncological issues, ankle arthrodesis, and ankle fractures.
SPSS version 25 (IBM, USA) was used for the data analysis.
In the pilot study, an independent t-test was applied to find out the discriminant validity between participants with and without chronic instability.
For the main study, internal consistency was determined by using Cronbach’s alpha. The scores that are ranged from 0.50 to 0.69 are considered as poor, 0.70 to 0.79 acceptable, 0.80 to 0.89 good, and the value of Cronbach alpha that is > 0.90 is considered excellent .
Convergent validity was determined by the Spearman correlation with FAOS subscales (pain, stiffness, sports, and quality of life). Convergent validity was determined by correlating with other scales FAOS. Negligible correlation ranged from 0.00–0.10, weak correlation range from 0.10–0.39, moderate correlation range is 0.40–0.69, strong correlation range is between 0.70–0.89, and very strong correlation is between 0.90–1.00 .
Factor analysis was done to determine the Construct validity was determined by using principal component analysis (PCA) with Varimax rotation. The proportion of variances in the variables by the underlying factors can be determined by the Kaiser–Meyer–Olkin (KMO) measure of sampling adequacy and Bartlett’s Test of Sphericity. [25,26,27].
Data summarization and data reduction are done in factor analysis and it is a powerful method for data reduction. Exploratory factor analysis describes the structure of underlying factors .
KMO is used for sampling adequacy to indicate the proportion of variance caused by the underlying factors and higher values that are close to 1 showed that the data is useful .
The factor loading for every item should exceed 0.5. The factor loading for every item should be 0.6 or higher according to Awang (2015). If any item has a factor loading less than 0.4 should be deleted from the measurement model .
Test–Retest reliability was measured with Intraclass correlation on week 1 and week 2 values. ICC2,1 values were calculated with 95% confidence intervals, values which were less than 0.5 indicated poor, 0.5–0.75 moderate, between 0.75 indicate good and > 0.90–1 excellent reliability .
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