The Body Dysmorphic Disorder Questionnaire-Aesthetic Surgery (BDDQ-AS) was developed by Lekakis et al. [12] It is a validated seven-item brief questionnaire used as a screening tool for body dysmorphic disorder (BDD) in aesthetic rhinoplasty patients. It consists of three dichotomous questions with "yes/no" answers and four questions with five-point Likert scales indicating severity. Screening is considered positive for BDD if the patient confirmed on the BDDQ-AS that he or she worries (question 1 = yes) and worries about his or her appearance (question 2 = yes) and that these worries cause him or her at least moderate distress or impairment in various areas of daily life (question 3 or 4 or 5 or 6 ≥ 3 or question 7 = yes).

According to the guidelines, the translation and cross-cultural adaptation of the original English version of the BDDQ-AS into the Mandarin version was carried out. Two native Mandarin speakers with appropriate medical knowledge (Y.L and M.Z) independently translated the questionnaire into simplified Chinese and produced two translation versions. Two preliminary M-BDDQ-AS versions were independently translated back into English by two bilingual expert translators and a plastic surgeon who were blinded to the original English version of the questionnaire. Finally, an expert committee was formed by the two forward translators, two backward translators, a methodologist, and the researchers. The two preliminary M-BDDQ-AS versions and the two backward translated English versions were compared with the original English version to obtain a pre-final M-BDDQ-AS version. To obtain a final version of the questionnaire, a pilot test was conducted with two test groups. The first group consisted of 20 native Chinese-speaking patients selected from our outpatient clinics and determined face validity using a dichotomous scale (clear/unclear). These 20 patients were not included in the final validation. The second group consisted of three senior plastic surgeons in the burns and Plastic Reconstructive Surgery department of West China Hospital and three dermatologists in the dermatovenerology department of West China Hospital, who determined the content validity index using a four-point Likert scale (1 = not relevant to 4 = very relevant). The content validity index for the items (I-CVI) and the content validity index for the scale (S-CVI) were calculated according to a previously published equation. Six members of the expert committee analyzed the pilot test results, including feedback and recommendations from the two test groups that identified specific changes that were needed in the pre-final questionnaire. Their work resulted in the final M-BDDQ-AS.

The study was conducted at the Burn and Plastic Reconstructive Surgery Department of West China Hospital of Sichuan University, a tertiary referral hospital in the People's Republic of China. One hundred and thirty-seven native Chinese patients seeking rhinoplasty were consecutively selected at the outpatient clinic. Exclusion criteria were inability to understand the questionnaire, severe physical deformities due to tumors or other diseases, and psychotic disorders.

A total of 137 patients were included in the validation phase of the study. Two surveys were conducted by an online survey platform, WJX (https://www.wjx.cn/). For the first survey, each patient was asked to scan a QR code that contained the corresponding M-BDDQ-AS questionnaire, an informed consent form, and a description of the study. All 137 patients responded to the first survey (7 male, 130 female). The second survey took place 2 weeks after the first survey (test–retest). Of these, 71 patients responded to the second survey (5 male, 66 female).

Psychometric validation of the final M-BDDQ-AS, including reliability (internal consistency, test–retest reliability), and item response theory analysis were examined as follows:

(1) Internal consistency: the Cronbach's α coefficient was used to examine the internal consistency of the instrument's reliability, and values equal to or greater than 0.7 were considered consistent. The Cronbach's α coefficient was calculated along with a two-sided 95% confidence interval (CI).

(2) Test–retest reliability: the reproducibility of the M-BDDQ-AS was verified by Intraclass Correlation Coefficient (ICC) by assessing the reliability of the responses between the first and second surveys. The analysis is based on the resolution index, and a value equal to or greater than 0.6 indicates that the instrument had a good level of reproducibility.

(3) Item response theory (IRT): the discrimination and difficulty parameters of the questionnaire were defined. A discrimination parameter describes the sensitivity of the test to distinguish symptoms of different severity. A difficulty parameter refers to the point of median probability at which 50% of the respondents affirm the correct answer on the questionnaire.

Prior to conducting the study, permission was obtained from Medical Ethics Committee the West China Hospital of Sichuan University.

Descriptive statistics were used to assess baseline demographic variables and pooled responses. Psychometric validation of the M-BDDQ-AS questionnaire was determined to assess its performance. All p-values were considered statistically significant if they were less than 0.05.

All the above statistical analyses were performed using Stata Data Analysis and Statistical Software, version 14.0 (StataCorp LP).