Validation of Uzbek SARC-F and IPAQ-SF Questionnaires in Adults With and Without Hypothyroidism

Adults aged 18 years or older with documented primary hypothyroidism, including those receiving levothyroxine replacement therapy. The planned group size is 240 participants. All participants will complete the Uzbek-language SARC-F and IPAQ-SF questionnaires and undergo standardised functional assessments. Approximately 100 participants will repeat both questionnaires after 7-14 days.

Adults aged 18 years or older without known thyroid disease and with thyroid function within the reference range. The planned group size is 240 participants. All participants will complete the Uzbek-language SARC-F and IPAQ-SF questionnaires and undergo standardised functional assessments. Approximately 100 participants will repeat both questionnaires after 7-14 days.

Test-retest reliability of the Uzbek-language Strength, Assistance in Walking, Rise From a Chair, Climb Stairs, and Falls (SARC-F) questionnaire total score (range 0-10, with higher scores indicating greater functional difficulties) will be assessed using a two-way random-effects, absolute-agreement, single-measure intraclass correlation coefficient (ICC) with a 95% confidence interval (CI). Analyses will include clinically stable participants who complete both assessments.

Test-retest reliability of total physical activity assessed using the Uzbek-language International Physical Activity Questionnaire-Short Form (IPAQ-SF), expressed in metabolic equivalent of task minutes per week (MET-minutes/week) and transformed as log(1 + total MET-minutes/week), will be assessed using a two-way random-effects, absolute-agreement, single-measure intraclass correlation coefficient (ICC) with a 95% confidence interval (CI). Analyses will include clinically and behaviourally stable participants who complete both assessments.

Agreement between positive (SARC-F score ≥4) and negative (score <4) screening classifications at the two administrations, assessed using Cohen's kappa and percentage agreement.

Agreement between low, moderate and high physical activity categories at the two administrations, assessed using weighted kappa and percentage agreement.

Measurement error of the Uzbek-language Strength, Assistance in Walking, Rise From a Chair, Climb Stairs, and Falls (SARC-F) questionnaire total score (range 0-10; higher scores indicate greater functional difficulties and worse outcomes) will be assessed using the standard error of measurement (SEM), smallest detectable change at the 95% confidence level (SDC95), and Bland-Altman limits of agreement, based on repeated assessments in clinically stable participants.

SEM, SDC95 and Bland-Altman agreement analysis, where appropriate, for repeated log(1 + total MET-minutes/week) values. Estimates on the transformed scale will be identified accordingly.

Spearman correlation between baseline SARC-F total score (0-10) and handgrip strength measured by dynamometry (kg). A negative association is hypothesised.

Spearman correlation between baseline SARC-F total score (0-10) and five-times sit-to-stand completion time (seconds). A positive association is hypothesised.

Spearman correlation between baseline SARC-F total score (0-10) and usual gait speed over 4 metres (m/s). A negative association is hypothesised.

Association between IPAQ-SF total physical activity (MET-minutes/week) and usual 4-m gait speed (m/s), assessed using Spearman correlation. A positive association is hypothesised.

Association between IPAQ-SF total physical activity (MET-minutes/week) and recorded mobility limitations. Participants with mobility limitations are hypothesised to report lower physical activity.

Exploratory Spearman correlation between the SARC-F total score and IPAQ-SF total physical activity (MET-minutes/week). A negative association is hypothesised.

Distribution of total and item scores, floor and ceiling effects, corrected item-total correlations and internal consistency of the five-item SARC-F questionnaire.

Percentage of participants obtaining the minimum possible total score of 0 on the Uzbek-language Strength, Assistance in Walking, Rise From a Chair, Climb Stairs, and Falls (SARC-F) questionnaire (range 0-10; higher scores indicate greater functional difficulties). The floor effect will be reported as a percentage.

Percentage of participants obtaining the maximum possible total score of 10 on the Uzbek-language Strength, Assistance in Walking, Rise From a Chair, Climb Stairs, and Falls (SARC-F) questionnaire (range 0-10; higher scores indicate greater functional difficulties). The ceiling effect will be reported as a percentage.

Baseline total score of the Uzbek-language Strength, Assistance in Walking, Rise From a Chair, Climb Stairs, and Falls (SARC-F) questionnaire, ranging from 0 to 10 points. Higher scores indicate greater functional difficulties. The distribution will be described using the median and interquartile range.

Total physical activity will be assessed using the Uzbek-language International Physical Activity Questionnaire-Short Form (IPAQ-SF). Weekly physical activity will be calculated from walking, moderate-intensity and vigorous-intensity activities according to the IPAQ-SF scoring protocol and expressed in metabolic equivalent of task minutes per week (MET-minutes/week). Higher values indicate greater reported physical activity. The measure has no fixed maximum score.

Physical activity will be classified as low, moderate or high using the established scoring criteria of the International Physical Activity Questionnaire-Short Form (IPAQ-SF). The number and percentage of participants in each category will be reported. Categories reflect increasing levels of reported physical activity.

Self-reported sitting time during a usual weekday over the preceding seven days will be assessed using the sitting item of the Uzbek-language International Physical Activity Questionnaire-Short Form (IPAQ-SF). Sitting time will be expressed in minutes per day. Higher values indicate longer sedentary time. Valid values range from 0 to 1,440 minutes per day.

The percentage of participants with invalid or implausible baseline responses to the Uzbek-language International Physical Activity Questionnaire-Short Form (IPAQ-SF) will be determined using prespecified data-cleaning and scoring rules. Each participant will be classified as having either valid or invalid/implausible responses. The outcome will be reported as the percentage of participants classified as invalid/implausible.