Based on the preliminary concept, the development of the questionnaire includes item development, questionnaire development and evaluation [18, 19]. This mixed research was performed during the period from March to June 2021 in China. According to the inclusion and exclusion criteria, the participants were identified and then included them on a voluntary basis.
Inclusion criteria: diagnosed with BC; positive ER and/or PR; receive AET for more than 1 month; women over the age of 18 with breast cancer; and volunteer to participate in the study.
Exclusion criteria: women with other critical diseases (such as severe infection, malignant tumors, malignant hypertension, myocardial infarction, severe cerebrovascular accident, heart failure, etc.).
Item development
The related literature of PSA in breast cancer women with AET were reviewed. This qualitative study was conducted by interviews and participatory observation [20]. The qualitative study data and literature of participants (n=16) provided abundant data for the development of the item pool and initial questionnaire. Psycho-social adaptation of breast cancer women with AET was closely related to emotional response, self-cognitive, and social situation.
Questionnaire development
5 experts (2 breast cancer specialists, 2 psychologists, and 1 nursing specialist) assessed the content validity of questionnaire by 2 rounds of consultation. In preparation for the formal survey, participants meeting the criteria were chosen prior to the survey, and the difficulty, suitability, and complexity of the item was assessed.
Investigation
The questionnaire was divided into two steps. 300 participants were used to perform item analysis, internal consistency reliability, and exploratory factor analysis. Test–retest, criterion validity, and confirmatory factor analysis of the questionnaire were performed with 96 respondents. The cases included in each subsample meet the requirement of 5-10 times the sample size. The survey instruments were as follows.
Sociodemographic characteristics include population and disease-related variables. A PSA questionnaire among BC women with AET was developed. The answers were scored on a 5-point Likert scale: all the time, often, sometimes, rarely, and never. The higher the score, the better the PSA. The 10-items General Self-Efficacy Scale (GSES) developed by Schwarzer in 1981 was widely used to measure the self-efficacy, which has been shown to have good reliability and validity.
The items were analyzed by CR value, DI, and ITC. And the items below the standard value are deleted. The construct validity was assessed by exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). The internal consistency of a questionnaire was evaluated by Cronbach's alpha coefficient. Test-retest reflects the stability and consistency of the test in time. After 10-18 days, 31 patients answered the questionnaire again, and the correlation coefficients of the two measures were used to assess the reliability of the retest. Spearman correlation coefficient test was used to reflect the validity of the scale stability. GSES was used to assess criterion validity [21].
Statistical analysis
If an item is not answered, the score is replaced by an average. If two or more questions are not answered, the questionnaire will be excluded from the analysis. In the qualitative phase, all data was managed and analyzed using Nvivo 11.0. In the quantitative stage, IBM SPSS Statistics 25.0 and AMOS 23.0 were used for statistical analysis.