Abstract
Background
The BODY-Q Chest module is a patient-reported outcome (PRO) instrument that measures satisfaction with how the chest (10 items) and nipples (5 items) look. This PRO instrument was previously field tested in an international sample of people seeking treatment for gynecomastia (n = 174), weight loss (n = 224), and chest masculinization (n = 341).
Objectives
The aim of this study was to examine the psychometric performance of the BODY-Q Chest module in a new chest masculinization surgery sample.
Methods
Data were collected from patients attending a private plastic surgery outpatient clinic in Canada between January 2018 and June 2019. Rasch measurement theory analysis was used to examine how the scales performed psychometrically.
Results
The sample provided 266 assessments (115 preoperative, 151 postoperative). All items had ordered thresholds, providing evidence that the 4 response options for each scale worked as expected. Item fit was within ±2.5 for all items, with all Bonferroni adjusted chi-square values nonsignificant. The data for the chest (χ2(20) = 18.72, P = 0.54) and nipples (χ 2(10) = 12.28, P = 0.27) scales fit the requirements of the Rasch model. Reliability was high with person separation index and Cronbach’s α values of ≥0.95 for the chest and ≥0.87 for the nipple scales, respectively. More depressive symptoms on the Patient Health Questionnaire-9 and lower health-related quality of life scales were weakly correlated with worse scores on the chest and nipple scales (P < 0.001).
Conclusions
The BODY-Q Chest module was shown to be scientifically sound in an independent sample of patients seeking chest masculinization surgery.
Surgical treatments available to transgender people can aid in the treatment of gender dysphoria.1,2 Gender-affirming surgery can dramatically change how the face, breast/chest, and genitals look and function. Being able to measure outcomes of these surgeries is important for clinicians, who need to know the outcomes associated with different surgical treatments in order to provide evidenced-based, patient-centered care.3 A barrier to outcome assessment in gender-affirming healthcare is the lack of patient-reported outcome (PRO) instruments designed specifically to measure the concerns most important to people seeking such treatment.4,5 A PRO instrument is needed because how a patient feels and functions before and after gender-affirming treatment are concepts of interest best assessed by the patient. Because of the number of different types of treatments affecting multiple areas of the body, it is likely that a tool with multiple scales will be needed to capture the range of outcomes important to this population. To address the call for a PRO instrument for gender-affirming care, our team is developing GENDER-Q, a set of independently functioning scales to measure the array of outcomes in this population.6
As a precursor to the development of GENDER-Q, our team developed and validated 2 scales, for chest and nipples, as part of a Chest module that supplements the BODY-Q. The BODY-Q is a PRO instrument designed to measure appearance and health-related quality of life (HR-QOL) outcomes for weight loss or body contouring. The BODY-Q Chest module7 was developed after the initial set of BODY-Q scales were published8-10 to provide a means to evaluate chest and nipple appearance from the patient’s perspective. We followed a 3-phase mixed-methods approach that is described in detail elsewhere.7 To summarize, in phase 1, scales to measure the appearance of the chest and nipples were drafted and refined by qualitative methods. In phase 2, the scales were field tested in an international sample (Canada, United States, Denmark, Netherlands) that included 739 adolescents and adults with different chest indications (ie, 174 gynecomastia, 224 weight loss, and 341 chest masculinization).7 A modern psychometric approach called Rasch measurement theory (RMT) analysis11 showed that all 10 chest and 5 nipple items had ordered thresholds and good item fit. Furthermore, data for both the scales fit the Rasch model, and the scales evidenced reliability and validity. We concluded that the BODY-Q Chest module was clinically meaningful and scientifically sound and could be used to measure outcomes for chest masculinization surgery.
Further assessment of the psychometric properties of the BODY-Q Chest module in independent clinical samples is crucial to ensuring its appropriate use in clinical practice and research. Further assessment of measurement properties is valuable to help strengthen evidence for the reliability and validity of this PRO instrument. The aim of this psychometric study was to further examine the psychometric properties of the chest and nipples scales in a new sample of Canadians receiving chest masculinization surgery.
METHODS
Before starting the study, research ethics review board approval was obtained from the Hamilton Integrated Research Ethics Board in Hamilton, Ontario. Participants were recruited from a private outpatient plastic surgery clinic (McLean Clinic, Mississauga, Ontario), between January 2018 and June 2019. This private practice treats patients from across Canada, with approximately 10% coming from outside Ontario, 40% from Northern Ontario, and 50% from the Greater Toronto Area. Eligible participants were aged 16 years and older, seeking chest masculinization surgery, and willing to complete a questionnaire booklet before surgery, as well as 6 weeks and 6 months after surgery.
The study was introduced at a clinic appointment to potential participants who were able to ask questions and then sign an informed consent letter if they agreed to participate. The consent letter asked for their email which was to be used to send 2 postoperative follow-up questionnaires. A secure web-based Research Electronic Data Capture (REDCap)12 survey was designed for data collection. The preoperative data were collected in the clinic with an iPad or paper booklet depending on the preferences of the patient and clinic logistics. To collect the postoperative data, participants were sent an email with a link to the survey. Emails were sent 6 weeks and 6 months after the surgery with a reminder sent 1 week after the initial email. An attempt was made before the end date of the study to reach nonresponders by telephone to encourage them to complete the survey.
The survey included the BODY-Q Chest module,7 which comprise a 10-item chest scale and a 5-item nipple scale. These scales ask respondents to indicate how satisfied they are (very dissatisfied, somewhat dissatisfied, somewhat satisfied, very satisfied) with the appearance of their chest and nipples, and to answer with the past week in mind. At the end of each scale, a stand-alone item was added to determine overall satisfaction with the appearance (very dissatisfied, somewhat dissatisfied, somewhat satisfied, very satisfied) of chest and nipples.
In addition to the BODY-Q Chest module, the participants also completed 2 additional PRO instruments: the Patient Health Questionnaire-9 (PHQ-9) and the Euro-Qol-5D (EQ-5D). The PHQ-9 scale measures the severity of depression.13 This scale’s psychometric properties (test-retest reliability, content validity, construct validity) have been examined in 14 validation studies.14 For the PHQ-9, in cases where 2 or fewer items were missing, values were imputed from the mean.15 Higher scores on the PHQ-9 indicate more depressive symptoms. The EQ-5D16 is a generic measure of HR-QOL developed by the EuroQoL Group. This 5-item questionnaire grades problems with mobility, self-care, usual activities, pain/discomfort, and anxiety/depression on 3 levels (no problem, some/moderate problems, extreme problems). The 3 levels of the EQ-5D can be reported as vectors ranging from 11111 (full health) to 33333 (worst health) to describe 243 unique health states. The EQ-5D has been used in studies to monitor the health status of individual patients and general populations, assessing the effects of conditions over time, and to estimate quality-adjusted life years in cost-effectiveness analyses.17 The EQ-5D was scored according to the Canadian valuations of the EQ-5D health states developed by Bansback et al.18
The participant demographics (age, body mass index [BMI], and surgery-related variables [number and type of complication]) were obtained from a case report form completed by the clinic staff. BMI was categorized according to the definitions provided by the Centers for Disease Control: <18.5 kg/m2 underweight, 18.5 to 25 kg/m2 normal, 25 to 30 kg/m2 overweight, ≥30 obese kg/m2.19
For the analysis, the data were downloaded from REDCap into SPSS version 25.0 for Windows/Apple Mac (IBM Corporation, Armonk, NY). For the RMT analysis, the data were imported into RUMM2030 software (RUMM Laboratory Pty Ltd, Duncraig, Australia). In the RMT analysis, data collected from the sample (observed data) were compared against the stringent requirements of the Rasch model.11 Tests and criteria are shown in Table 1 and are described elsewhere in detail.20
Table 1.
Statistical and Graphical Tests Performed as Part of the RMT Analysis
| Test | Description |
|---|---|
| Unidimensionality | We computed principal component/independent t test analysis by the methods proposed by Smith.21 Item residuals with the strongest loading (positively and negatively) on the first principal component were identified and used to conduct independent t tests. Multidimensionality was assumed if >5% of the t tests were significant. |
| Thresholds for item response options | We examined whether the response options worked as intended by inspecting the threshold maps. Disordered thresholds can indicate where respondents may have misunderstood response options or used the response options in an inconsistent manner. |
| Item fit statistics | The overall fit of the data to the Rasch model was evaluated by chi-square analysis. A nonsignificant chi-square indicates no substantial deviation of the data from the model. The fit of each item to the Rasch model was examined statistically (fit residuals within ±2.5, Bonferroni-adjusted chi-square values) and graphically (item characteristic curves). Evidence from these tests was interpreted together to confirm fit of the data to the Rasch model. |
| Local dependence | The extent to which items are not dependent on other items was determined by examining the residual correlation matrix. For any pairs of items that correlated >0.20, a subtest was computed to determine the impact of the correlation on scale reliability. |
| Targeting | Scale-to-sample targeting was examined by comparing the spread of person and item locations to determine whether items are evenly spread over a reasonable range that matches the range of the construct reported by the sample. |
| Person separation index | This statistic measures the error associated with the measurement of people in a sample. Higher values show greater reliability. |
| Cronbach α | This statistic is a measure of how closely a set of items in a scale are related (ie, internal consistency). Higher values indicate greater reliability. |
For each BODY-Q scale, the raw scores for items are added and converted into a score that ranges from 0 (worse) to 100 (best) based on the transformation of logits from the analysis of the international field-test study.9 Missing data for the chest and the nipple scales were imputed by the half-rule method, where the mean was substituted for missing values if at least 50% of the items in the scale were answered. We examined relations with scores for the PHQ-9 and EQ-5D with Spearman’s rank-order correlation. In the original BODY-Q Chest module field-test study, correlations between the BODY-Q chest, nipple, psychological, and social scales were small (0.20-0.39). Therefore, for validity testing, we hypothesized that more depressive symptoms on the PHQ-9 and lower HR-QOL scores on the EQ-5D would be correlated with worse appearance scale scores, but that the correlations would be weak (<0.30).
RESULTS
A total of 120 participants were introduced to the study, and 115 consented to take part (a response rate of 95.8%), completing 266 assessments across the 3 time points.
Table 2 shows the sample characteristics. The mean [standard deviation] age of the participants was 26 [7] years (range, 16-61 years), and their mean BMI was 27.1 [5.8] kg/m2 (range, 17.5-46.8 kg/m2), with 54.8% of participants classified as overweight or obese. In the postoperative cohort, 17 reported a single complication, and 6 reported multiple complications. The most common complications were dog ear (n = 9), hematoma (n = 8), and seroma (n = 7). Other complications included necrosis of the nipple and delayed wound healing (n = 5).
Table 2.
Characteristics of the Study Sample (n = 115)
| n | % | |
|---|---|---|
| Age, years (n = 114) | ||
| 16-19 | 18 | 15.8 |
| 20-29 | 72 | 63.2 |
| 30-39 | 20 | 17.5 |
| ≥40 | 4 | 3.5 |
| BMI at baseline (n = 113) | ||
| Underweight | 3 | 2.7 |
| Normal | 48 | 42.5 |
| Overweight | 31 | 27.4 |
| Obese | 31 | 27.4 |
| Complications (n = 110) | ||
| 0 | 87 | 79.1 |
| 1 | 17 | 15.5 |
| >1 | 6 | 5.5 |
| Number of assessments completed by time point (n = 266) | ||
| Preoperative | 115 | 43.2 |
| 6-week postoperative | 81 | 30.5 |
| 6-month postoperative | 70 | 26.3 |
In the RMT approach, the items of a scale are meant to map out a clinical hierarchy for the concept being measured. Therefore, the assumption is that a scale is unidimensional. The principal component analysis/independent t test showed that the chest (5.8%) and nipple (5.5%) scales slightly exceeded the 5% proportion of statistically significant t tests.
Figures 1 and 2 show that all 15 items had ordered response options. In addition, all 15 items fit within the ±2.5 criteria and had chi-square P values that were nonsignificant (Table 3). One pair of items in the chest scale had a residual correlation of 0.44 (shape without shirt on and mirror without shirt on). The subtest performed showed no drop in the person separation index (PSI) values, indicating the correlation did not affect scale reliability.
Figure 1.
Threshold map for all items on the chest scale. The x axis shows the concept of interest (satisfaction with appearance), with higher scores (more satisfaction) increasing from left to right. The y axis and rectangular bars represent the response category for each item: 0 = very dissatisfied, 1 = somewhat dissatisfied, 2 = somewhat satisfied, and 3 = very satisfied.
Figure 2.
Threshold map for all items on the nipple scale. The x axis shows the concept of interest (satisfaction with appearance), with higher scores (more satisfaction) increasing from left to right. The y axis and rectangular bars represent the response category for each item: 0 = very dissatisfied, 1 = somewhat dissatisfied, 2 = somewhat satisfied, and 3 = very satisfied.
Table 3.
Rasch Measurement Theory Statistical Indicators of Item Fit
| Item fit statistics | |||||||
|---|---|---|---|---|---|---|---|
| Items | Location | SE | Fit residual | DF | Chi-square | DF | P value |
| Chest | |||||||
| in loose t-shirt | –1.67 | 0.16 | –1.00 | 135.53 | 2.62 | 2.00 | 0.27 |
| when lie on back | –1.61 | 0.16 | 0.64 | 135.53 | 0.17 | 2.00 | 0.92 |
| stand up straight | –0.27 | 0.18 | –2.46 | 135.53 | 6.40 | 2.00 | 0.04 |
| masculine | –0.19 | 0.16 | 0.22 | 132.01 | 3.35 | 2.00 | 0.19 |
| when active | 0.11 | 0.19 | –0.70 | 135.53 | 0.40 | 2.00 | 0.82 |
| in snug t-shirt | 0.38 | 0.19 | –0.09 | 133.77 | 0.80 | 2.00 | 0.67 |
| shape without shirt | 0.88 | 0.17 | –0.84 | 133.77 | 0.91 | 2.00 | 0.63 |
| when you bend over | 0.81 | 0.19 | 1.26 | 133.77 | 1.01 | 2.00 | 0.60 |
| profile without shirt | 0.95 | 0.18 | –1.75 | 133.77 | 1.17 | 2.00 | 0.56 |
| mirror without shirt | 0.63 | 0.17 | –1.58 | 133.77 | 1.89 | 2.00 | 0.39 |
| Nipples | |||||||
| shape | –0.34 | 0.13 | 2.04 | 141.80 | 0.48 | 2.00 | 0.79 |
| size | –0.18 | 0.13 | –2.46 | 142.58 | 4.51 | 2.00 | 0.11 |
| how flat | 0.14 | 0.13 | 0.56 | 141.80 | 0.88 | 2.00 | 0.64 |
| in snug t-shirt | –0.09 | 0.13 | 2.13 | 141.02 | 1.01 | 2.00 | 0.60 |
| without a shirt on | 0.46 | 0.13 | –2.06 | 141.80 | 5.41 | 2.00 | 0.07 |
SE, standard error; DF, degrees of freedom.
Data collected from the sample for the chest (χ 2(20) = 18.72, P = 0.54) and nipple (χ 2(10) = 12.28, P = 0.27) scales fit the requirements of the Rasch model, with nonsignificant chi-square values. The proportion of the sample to score on the scale was 58% for the chest scale and 73% for the nipple scale. These findings are illustrated in Figures 3 and 4, which shows the scale-to-sample targeting for the sample by whether they are pre- or postoperative. Although the items that form each scale mapped out a good continuum for each construct, some preoperative participants scored at the floor (very dissatisfied with all aspects of the appearance of their chest/nipples) and postoperative participants at the ceiling (very satisfied with all aspects of the appearance of their chest/nipples). Scale reliability was high as evidenced by PSI values with and without extremes for the chest (0.95, 0.96) and nipple (0.88, 0.87) scales. Cronbach α values with and without extremes were also high for the chest (0.99, 0.98) and nipple (0.95, 0.91) scales.
Figure 3.
Person frequency distribution for the chest scale. The x axis represents the concept of interest (satisfaction with appearance), with higher scores (more satisfaction) increasing to the right. The y axis shows the frequency of person measure locations.
Figure 4.
Person frequency distribution for the nipple scale. The x axis represents the concept of interest (satisfaction with appearance), with higher scores (more satisfaction) increasing to the right. The y axis shows the frequency of person measure locations.
The Kolmogorov-Smirnov statistic confirmed that the data for the chest and nipple scales were not normally distributed (P < 0.001), supporting the use of nonparametric tests. As hypothesized in the full sample, more depressive symptoms on the PHQ-9 and lower HR-QOL were weakly correlated with worse scores (less satisfaction with appearance) on the chest (PHQ-9, r = –0.333, P < 0.001; EQ-5D, r = 0.224, P < 0.001) and nipple (PHQ-9, r = –0.368, P < 0.001; EQ-5D, r = 0.249, P < 0.001) scales, respectively.
DISCUSSION
The results of this study build upon previous psychometric work providing further evidence for the reliability and validity of the BODY-Q Chest module in an independent sample of individuals seeking or receiving chest masculinization surgery. The BODY-Q Chest module rigorously measures patient outcomes in this patient population. The results of this study support the use of the BODY-Q Chest module in clinical practice and research. Clinicians can use this module in their practice to assess patients’ satisfaction with their chest before and after surgery.3 Such information could be used to set treatment expectations preoperatively and enhance patient-clinician communication, resulting in patient-centered decision-making.3 The results of the Rasch analysis also help to support the strong psychometric properties of the scales, as well as to identify some potential areas for improvement. In addition, the convergent validity with other commonly used PRO instruments in this population helps to provide evidence-based information to inform scale selection in this population.
As in the initial development study,7 Rasch analysis showed that the 2 BODY-Q Chest module scales each measured a clinical hierarchy. Some floor and ceiling effects were observed in this study for both the chest and the nipple scales. Floor and ceiling effects occur when respondents score at the top or bottom end of the scale instead of between the bottom and the top of the scale (ie, on the scale). These effects were higher than those observed in the original development study, which included patients seeking chest surgery for a variety of reasons. In the original study, 24% of the respondents scored outside the scale’s measurement on both the chest and nipple scales, compared with 42% and 27%, respectively, in the current study. The floor and ceiling effects align with the finding that the transgender male sample reported the lowest mean scores on the chest and nipple scales before surgery and the highest mean scores after surgery. Future research to develop the GENDER-Q6 with RMT analysis provides an opportunity to potentially create and field test new items for these 2 scales to help improve targeting to this patient population.
The correlations between the BODY-Q Chest module scales and the PHQ-9 and EQ-5D provide evidence that the constructs measured in these other instruments correlate with appearance, but only weakly. The correlations illustrate the importance of selecting the right PRO instruments to evaluate surgical outcomes, because the instrument chosen may lead to different conclusions. Past studies have used a variety of PRO instruments to examine outcomes in transgender men, including generic HR-QOL tools, ad hoc questionnaires, and specific measures not designed for use in this population.5 A 2018 systematic review of 29 studies reporting outcomes for treatment-seeking transgender men showed that only 2 studies used a PRO instrument (a transgender self-evaluation questionnaire) specifically designed and validated for the transgender population.22 Instead, many of the studies included used generic questionnaires, including the Short Form-36 Health Survey, WHOQOL, Subjective Quality of Life Analysis, and King’s Health Questionnaire.22 A weakness of generic HR-QOL measures is that these measures do not necessarily capture the outcomes that are most important to a specific patient group. By not measuring concepts important to patients, improvements related to a specific treatment may be missed. Other studies have applied ad hoc questionnaires.23 Ad hoc questionnaires have not undergone rigorous development or validation as described in best practices for the development of PRO instruments.24-26 Results from studies that use ad hoc measures are not comparable with results from other studies and cannot be included in systematic reviews looking to assess treatment outcomes across studies.
Other studies have modified or applied existing PRO instruments designed for other populations. Two studies27,28 utilized the BREAST-Q to research outcomes in transgender men having chest masculinizing surgery. A limitation of these studies is that the development of BREAST-Q did not target participants who were transgender or nonbinary. The BREAST-Q was designed for women undergoing breast surgery and includes separate modules for breast cancer, augmentation, and reduction/mastopexy.29 In order to ensure high-quality evidence for transgender healthcare, research needs to apply validated measures with strong psychometric properties. Future studies of chest masculinization surgery should use the BODY-Q Chest module instead of the BREAST-Q, as its content was purposely designed to evaluate appearance of the chest and nipples in this context. Furthermore, the current study and previous field-test study provide evidence of the reliability and validity of the BODY-Q Chest module for use in transgender men.7
A limitation of this study is that the sample was recruited from a single clinic in Canada. However, 96% of patients at the McLean Clinic who were approached agreed to participate in this study, showing a keen interest in this type of research in this population. Despite the high consent rate, the representativeness of the sample to the Canadian transgender male population is unknown. Currently, 24 sites in 7 provinces across Canada provide access to chest masculinization surgery, 6 of which are in Ontario.30 Future research could examine outcomes of chest surgery at other clinics in Canada and internationally. Further, it would be interesting to examine how many participants returned to the operating room due to their complications, and how that affected the responses on the Chest module. This was not addressed in this paper. Another limitation of this study is that test-retest reliability was not examined, which is a crucial psychometric property of PRO instruments. In addition, we were not able to examine concurrent validity as there are no other PRO instruments that measure chest appearance that we could include for comparative purposes. Finally, an examination of responsiveness was beyond the scope of the current paper but is the focus of a separate publication.
CONCLUSIONS
With an increasing demand for chest masculinization surgery,31 it is essential to have carefully designed, psychometrically sound PRO instruments. The BODY-Q Chest module was developed by following international guidelines for PRO instrument development to fill an evident gap in the availability of PRO instruments for evaluating chest masculinization surgery. The module’s 2 scales for chest and nipples can be used both clinically and in research to inform treatment decisions and assess outcomes. Research to develop the GENDER-Q will soon provide a comprehensive set of scales to measure outcomes for other gender-affirming treatments.
Disclosures
The Chest module of the BODY-Q is jointly owned by Memorial Sloan-Kettering Cancer Center and McMaster University. Drs Pusic and Klassen are co-developers of other BODY-Q modules and receive a share of license revenues based on inventor-sharing policies. The other authors declared no potential conflicts of interest with respect to the research, authorship, and publication of this article.
Funding
This study was funded by the Canadian Institutes of Health Research (CIHR) Strategy for Patient-Oriented Research (SPOR) Collaboration Grant.
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