Validation of the Thai version of the Female Genital Self-Image Scale (FGSIS) | BMC Women’s Health


This study was conducted at the Outpatient Clinic of Department of Obstetrics and Gynecology, Ramathibodi Hospital Faculty of Medicine, Mahidol University, Bangkok, Thailand, between December 2020 and January 2021. The validation procedure included two phases: ( 1) translation and (2) testing of psychometric properties.

Translation of phase 1

The cross-cultural adaptation of the original English FGSIS into a Thai version was carried out according to the process of patient-reported outcome measures [18]. We began the translation process after obtaining written permission to use the FGSIS from the scale developer, Debra Herbenick.

  1. (1)

    Two Thai language translators experienced in translating health questionnaires independently performed the direct translation of the FGSIS into Thai.

  2. (2)

    An expert experienced in the Questionnaire Validation (CS) process compared and combined the two direct translations into a reconciled Thai version.

  3. (3)

    Two bilingual native English speakers, who had not seen the original version of the scale and were unaware of the purpose of the study, individually translated the reconciled Thai version into English.

  4. (4)

    The two reverse translations were then reviewed by two gynecologists (WK and AK), a nurse (SS) and the questionnaire validation expert (CS) to ensure the accuracy of the translation. Any misunderstandings or unclear expressions in the translated versions have been reviewed and revised to produce a final Thai version.

Phase 2 Psychometric Properties Test

The validity and reliability of the Thai FGSIS was assessed in a cross-sectional psychometric study of women attending a health check-up clinic during the study period. Based on voluntary and non-probability sampling method, eligible participants were recruited according to inclusion and exclusion criteria. Eligible participants were sexually active women (who had had any type of sex at least once in the previous month) who wished to participate, were able to communicate fluently in Thai, and had provided written informed consent. Participants were excluded from the study if they withdrew or were unable to complete the questionnaire. No compensation of any kind has been provided.

The final version of the Thai FGSIS was assessed using the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology to assess the content validity of patient-reported outcome measures. [19]. The psychometric properties examined were content validity, face validity, internal consistency, construct validity, and test-retest reliability. The details of the stages of the psychometric tests are as follows.

  1. (1)

    Content validity (including face validity) was assessed using the COSMIN methodology [19]. The final version of the questionnaire was tested on a heterogeneous group of twenty lay Thai women. Participants were asked to complete the final version of the questionnaire and provide feedback on incomprehensible words, level of difficulty and cultural relevance of the translation. They could discuss any general or specific questions with the principal investigator (WK), who observed the volunteers completing the questionnaire and monitoring the pilot procedure. At the end, participants were briefly quizzed on the meaning of each item. At the same time, five obstetrician-gynecologists and a psychiatrist were asked to review the final draft questionnaire by a clinician. Additionally, levels of missing data were also measured and used as an indicator of inappropriate items. The results of the pilot tests were taken into account when producing the final version of the Thai FGSIS used in the study. Since the content validity of the original FGSIS questionnaire has been demonstrated previously [1]this study only tested the interpretability of the items in terms of questionnaire response time [19].

  2. (2)

    Internal consistency or reliability was assessed by examining correlations between questionnaire items. Cronbach’s alpha and item-total correlations were calculated to assess test item consistency.

  3. (3)

    We hypothesized that genital self-image is closely associated with sexual functioning. Therefore, we predicted that genital self-image scores would be positively and strongly correlated with sexual functioning scores. We compared FGSIS and FSFI scores to examine the construct validity of the Thai FGSIS. Convergent validity was used as evidence in support of construct validity.

  4. (4)

    Test-retest reliability is a measure of the stability of survey results. The stability of the Thai FGSIS was measured by administering the questionnaire to the same group of respondents, with an interval of 2 weeks between the first and the second test. All participants were invited to participate in the retest.


The FGSIS was methodically developed and psychometric testing has shown the scale to have good validity and reliability [2, 3]. The FGSIS includes seven items that assess women’s feelings and beliefs about their own genitalia. The answers are on a decreasing scale of 4 points (strongly agree, agree, disagree, strongly disagree). Respondents’ scores for each item are added together to obtain a total score (range of 7 to 28). There is no end point; higher scores indicate a more positive genital self-image [1].

The FSFI is a self-report questionnaire developed to measure female sexual function over the previous 4 weeks. It consists of 19 elements that encompass six distinct domains: desire, arousal, lubrication, orgasm, satisfaction and pain. Response scores range from 1 to 5; higher scores indicate better sexual functioning [12, 13]. The FSFI has been widely used and translated into several languages, including Thai [20].

Ethical considerations

The study was approved by the Human Research Ethics Committee of the Faculty of Medicine, Ramathibodi Hospital, Mahidol University (MURA 2020/1777). All participants signed an informed consent form before being enrolled in the study. Permission was obtained from the original FGSIS author to translate the scale into Thai. All methods were performed in accordance with the Declaration of Helsinki for medical research involving human subjects.

statistical analyzes

The demographic and baseline characteristics of the study population were described as mean and standard deviation (SD) or number and percentage for categorical data. Content validity of the Thai FGSIS was assessed using the missing values ​​model, and internal consistency was determined using Cronbach’s alpha [21]. The convergent validity of the Thai-FGSIS was examined by Pearson correlations between the Thai-FGSIS total scores and six domains of sexual functioning and FSFI. Additionally, the factor structure was examined with confirmatory factor analysis (CFA) and used to determine the construct validity of the Thai-FGSIS [22,23,24]. A series of CAs were performed to determine how well the model fit the observed data. The CFA was performed with a maximum likelihood estimate on the seven items of the questionnaire. A combination of fit indices was used to assess the overall fit of the model, including the chi-square (χ2) goodness-of-fit statistic, comparative fit index (CFI), Tucker-Lewis index (TLI), root mean square error of approximation (RMSEA), and standardized root mean square residual (SRMR). Test-retest reliability was assessed by comparing mean test-retest scores for each domain using intraclass correlation coefficients [25].

The test results were considered statistically significant at p

Sample size estimation

Satisfy the 10 recommended ratios of respondents per item for the required sample size in a validation study [26]validating a seven-item questionnaire requires a sample size of 70. Therefore, the required sample size was estimated at 84 to allow for a 20% dropout rate.

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