Title:
Measuring reliability and validity of a newly developed stress instrument: Newly Diagnosed Breast Cancer Stress Scale.

Abstract:
To assess the reliability and validity of a developed instrument entitled Newly Diagnosed Breast Cancer Stress Scale.
Distress, clinical anxiety and depression are evident in patients with cancer, leading to poor psychosocial and quality-of-life outcomes.
Instrument development study with norm-referenced measurements.
Content validity was determined by expert review. Cronbach's α was used to assess internal consistency reliability and product-moment correlations were conducted. Exploratory factor analysis measured validity of items using varimax rotation method. Criterion-related validity testing used the Perceived Stress Scale and the convergent validity test of construct validity used the Hospital Anxiety and Depression Scale. A total of 125 women pathologically diagnosed with breast cancer were interviewed on the day prior to initial breast surgery.
After testing, the Newly Diagnosed Breast Cancer Stress Scale consisted of four main factors with 17 items with acceptable reliability and good validity, and its length and time to complete the questionnaire were appropriate. Internal consistency reliability of the scale was shown by Cronbach's α = 0·84, the criterion validity of Perceived Stress Scale-10 was r = 0·46 (p < 0·001), the convergent validity of Hospital Anxiety and Depression Scale-14 was r = 0·57 (p < 0·001) for anxiety and r = 0·35 (p < 0·001) for depression.
The Newly Diagnosed Breast Cancer Stress Scale has acceptable reliability and good validity to measure stress in newly diagnosed patients with breast cancer.
The Newly Diagnosed Breast Cancer Stress Scale can provide healthcare workers with an instrument to better identify stress levels in newly diagnosed breast cancer patients and provide valuable information when defining psychosocial care interventions.