The study protocol and consent form were both approved by the Siriraj Institutional Review Board (SIRB) of the Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand (COA no. Si 749/2019). This study was conducted in accordance with the principles described in the Declaration of Helsinki and all of its later amendments. The original English language version of the self-rated FRQ was translated into Thai language using a forward-backward translation technique according to guidelines proposed by Beaton et al. [12]. This process involves two translations of the self-rated FRQ from English to Thai, one by a professional English translator and one by a bilingual physician. The two translations were then reviewed and adapted into one version. Backward translation from Thai into English was performed by a local professional translator who had no access to or awareness about the original self-rated FRQ. The backward version was then compared to the original English self-rated FRQ to identify any discrepancies. This process resulted in the development of the final version. Afterwards, a group of experts in falls in older adults with osteoporosis that consisted of 2 orthopedic surgeons, 1 physiatrist, 1 geriatrician, and 1 fracture liaison service nurse were asked to evaluate the content validity of the self-rated FRQ. Each expert was asked to rate each item on the self-rated FRQ with a score of 1 (agree), 0 (unsure/ unclear), or − 1 (disagree) to evaluate the content validity. The average score of each questionnaire item was then used to calculate the index of item-objective congruence. We affirmed the understandability of the questions by exposing 15 randomly selected osteoporotic patients to the self-rated FRQ as the final step of the translation protocol.
Validation
Patients
The authors prospectively enrolled patients from the outpatient orthopedic unit of the Department of Orthopedic Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand from December 2019 to March 2020. We included men and postmenopausal women aged more than 65 years who were diagnosed with osteoporosis by bone mineral density (BMD) T-score ≤ − 2.5 or by history of low-energy hip or vertebral compression fracture (VCF). Patients with severe cognitive and/or neurological impairment (e.g., dementia), deafness, or severe cardiopulmonary diseases for whom it would not be safe to undergo performance-based testing were excluded. All included patients were evaluated by the same investigator (NK). Data, including age, gender, body mass index, Charlson comorbidity index, type of surgery, pre-injury walking status, and living condition, were collected and recorded. Written informed consent was obtained from each patient who participated in this study.
Outcome measurement tools
Each participant was asked to complete the self-rated FRQ and the Thai Falls Risk Assessment Test (Thai-FRAT). Participants were also asked to perform the 3 following performance-based tests: BBS, TUG test, and the 5 times sit-to-stand test (5TSTS test). To determine the test-retest reliability of the self-rated FRQ, a second copy of the self-rated FRQ was provided to the first 30 patients in a stamped, self-addressed envelope. One week later, those patients were reminded by telephone to complete the provided second copy of the self-rated FRQ, and to return it by Thailand Post to the research team.
Self-rated fall risk questionnaire (self-rated FRQ)
The self-rated FRQ, which is the fall risk screening component of the STEADI algorithm [13], comprises 12 questions specific to individual physical functional performance and different fall risk factors. Each question can be scored as 0 or 1, or 0 or 2 depending on the question, and the total possible score is 14. A higher score indicates a higher risk of falling. The original version of the self-rated FRQ was shown to have good validity and reliability for evaluating older adult patients who are at high risk of falling with a cutoff value of 4 [11, 14]. If a patient scored 4 points or more, their fall risk was considered to be increased.
Thai falls risk assessment test (Thai-FRAT)
Thai-FRAT is a fall risk assessment tool that was developed by a group of Thai investigators in 2008 to assess fall risk in Thai community-dwelling older adults. It consists of 6 items that identify fall risk factors, including gender, visual impairment, balance impairment, medication use, history of falls, and type of residence. The scoring range varies according to the item for a possible total score of 11. Thai-FRAT has good validity and reliability for identifying older adult patients who are at high risk for falling with a cutoff value of 4 [15]. If a patient scored 4 points or more, their fall risk was considered to be increased.
Berg balance scale (BBS)
BBS is a performance-based test that asks patients to perform 14 tasks that are used to assess patient balance. Each task has a 5-point scale with a scoring range from 0 to 4 for a maximum total score of 56. A lower score indicates higher risk for falls. BBS has good validity and reliability for identifying older adult patients who are at high risk for falls with a cutoff value of 45 [16]. If a patient scores less than 45 points, their fall risk was regarded as being increased.
Timed get-up-and-go test (TUG test)
Patients were asked to stand up from a high-seated chair, walk to a mark 3 m away at a comfortable pace, and then return to a sitting position [17]. Patients were allowed to use their arms when getting up from or sitting down in the seat. Patients were asked to perform this task three times, and the average time to complete the test was calculated and recorded. TUG test was reported to be a reliable tool for identifying risk of falls among older adult patients [18]. A threshold of 12 s was used as the cutoff value for detecting older adult patients at high risk for falling [18]. If patients took 12 s or longer to perform the TUG test, they were considered to be at possible risk of falling.
5 times sit-to-stand test (5TSTS test)
The 5TSTS test was conducted by asking patients to sit upright in an armless chair with a seat height of 43 cm with their arms crossed across their chest. The evaluator started timing after speaking the word “go”, after which patients stand up from a chair (without pushing off) and sit back down 5 times as quickly as possible. Timing stopped when the patients’ buttocks reached the chair after completing the fifth stand up-sit down cycle [19]. The current evidence demonstrates the efficacy of the 5TSTS for determining risk of falls in older adult patients with a cutoff value of 15 s [20]. If patients took longer than 15 s to perform the 5TSTS test, they were classified as being at higher risk of falling.
Data analysis
Data analyses were performed using SPSS Statistics version 18 (SPSS, Inc., Chicago, IL, USA). Kolmogorov-Smirnov test was used to assess the distribution of data. Content validity of the self-rated FRQ was determined using the index of item-objective congruence. Construct validity was evaluated by comparing scores from the self-rated FRQ with scores from the BBS, Thai-FRAT, TUG, and 5TSTS tests. Construct validity was determined using chi-square test and Spearman’s rank correlation coefficient. A Spearman’s rank correlation coefficient (r) of < 0.3 was considered poor; 0.3 to 0.5, fair; > 0.5 to 0.8, moderately strong; and, > 0.8, very strong [21]. Since osteoporosis can be diagnosed using BMD T-score or by the occurrence of a fragility fracture, osteoporotic patient with a history of fragility fracture may have different characteristics when compared to those without fracture. Therefore, we have further evaluated construct validity in these two subgroup populations.
Test-retest reliability of the self-rated FRQ was also tested using Kappa statistics. A Kappa value of 0.1 to 0.2 was considered slight; 0.21 to 0.4, fair; 0.41 to 0.6, moderate; 0.61 to 0.8, substantial; and > 0.8, almost perfect [21, 22]. Internal consistency of the self-rated FRQ was assessed using Cronbach’s alpha. A Cronbach’s alpha within the range of 0.8 to 0.9 was considered good, and a value ≥0.9 was considered excellent [23]. The distribution of scores was calculated to evaluate for ceiling and floor effect. A ceiling or floor effect was considered to exist if > 15% of subjects achieved the lowest or highest possible score [23].
The sample size was estimated based on correlation between two tests. We assumed that the self-rated FRQ had very good correlation with BBS (|r|, absolute r = 0.75). Using a 2-sided type I error of 0.05 and 90% power to test H0: ρ = 0.5 versus H1: ρ = 0.75, a sample of 62 subjects was required. To compensate for a 10% attrition rate for any reason, the sample size was increased to 68.