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Introduction The Perceived Stress Scale (PSS) is a widely recognized patient-reported outcome measure designed to assess an individual's level of perceived stress. The PSS consists of ten items, with six items phrased negatively and four phrased positively. Most studies have found that the PSS consists of two dimensions, with negative and positive items forming separate dimensions. However, some studies suggest a one-dimensional construct. Objective We aimed to investigate the dimensionality of the PSS and the impact of wording effects on the measurement properties of the scale. Methods We tested a modified version of the PSS (mPSS), with negative wording of all items. In a Danish sample, respondents were randomized to answer the PSS or the mPSS. We used confirmative factor analysis and Rasch analysis to assess the validity and reliability of the two versions. The proportion of person misfit was also evaluated. Results A total of 326 respondents completed the PSS, whereas 306 completed the mPSS. For the PSS, a two-factor model fitted the data best, and the first positively formulated item showed under-discrimination (Rasch model item fit rejected). The mPSS had higher measurement precision than the PSS, but evidence of local dependence was seen for both versions. Fewer respondents gave improbable responses to the mPSS compared to the PSS. Limitations Data comes from three different respondent samples. Conclusion The PSS was deemed essentially unidimensional, with the extra variance being attributed to the reversed items. To reduce response bias, clinicians and researchers may apply the mPSS., INTRODUCTION: The Perceived Stress Scale (PSS) is a widely recognized patient-reported outcome measure designed to assess an individual's level of perceived stress. The PSS consists of ten items, with six items phrased negatively and four phrased positively. Most studies have found that the PSS consists of two dimensions, with negative and positive items forming separate dimensions. However, some studies suggest a one-dimensional construct.OBJECTIVE: We aimed to investigate the dimensionality of the PSS and the impact of wording effects on the measurement properties of the scale.METHODS: We tested a modified version of the PSS (mPSS), with negative wording of all items. In a Danish sample, respondents were randomized to answer the PSS or the mPSS. We used confirmative factor analysis and Rasch analysis to assess the validity and reliability of the two versions. The proportion of person misfit was also evaluated.RESULTS: A total of 326 respondents completed the PSS, whereas 306 completed the mPSS. For the PSS, a two-factor model fitted the data best, and the first positively formulated item showed under-discrimination (Rasch model item fit rejected). The mPSS had higher measurement precision than the PSS, but evidence of local dependence was seen for both versions. Fewer respondents gave improbable responses to the mPSS compared to the PSS.LIMITATIONS: Data comes from three different respondent samples.CONCLUSION: The PSS was deemed essentially unidimensional, with the extra variance being attributed to the reversed items. To reduce response bias, clinicians and researchers may apply the mPSS.

Background The Major Depression Inventory (MDI) is a patient-reported outcome measure used by general practitioners to assist with diagnosing and evaluation of the severity of a patient's depression. However, recent studies have questioned the structural validity of the MDI. Objectives We proposed a modified version (mMDI) of the MDI with fewer response categories and four rephrased items and aimed to compare the psychometric properties of the changes in a joint cohort of patients from general practice and mental health associations. Methods We used Rasch analysis, confirmatory factor analysis, and the area under the receiver operating curve (AUROC) to assess the validity and reliability of the two versions. Equipercentile linking was used to compute cut-off points for the mMDI. Results For both versions, local dependence was found between the three item pairs (loss of interest, lack of energy), (lack of self-confidence, feelings of guilt), and (concentration problems, feeling restless/slowed down). The mMDI displayed lower measurement error in the upper end of the scale and better item level fit for three of the four reformulated items compared to the MDI. For the MDI, 5.3% of the respondents gave improbable responses; the corresponding number was 3.4% for the mMDI. The mMDI displayed better fit to a one-factor model compared to the MDI. When comparing the correlation of the scales with the WHO-5 instrument, the corresponding AUROC estimates for the mMDI and MDI were found to be 0.93 (0.92; 0.96) and 0.91 (0.87; 0.94), respectively. The cut-off points for mild, moderate, and severe depression in the mMDI were found to be 17, 20, and 23, respectively. Conclusion The proposed changes of the MDI are psychometrically sound upgrades of the original., BACKGROUND: The Major Depression Inventory (MDI) is a patient-reported outcome measure used by general practitioners to assist with diagnosing and evaluation of the severity of a patient's depression. However, recent studies have questioned the structural validity of the MDI.OBJECTIVES: We proposed a modified version (mMDI) of the MDI with fewer response categories and four rephrased items and aimed to compare the psychometric properties of the changes in a joint cohort of patients from general practice and mental health associations.METHODS: We used Rasch analysis, confirmatory factor analysis, and the area under the receiver operating curve (AUROC) to assess the validity and reliability of the two versions. Equipercentile linking was used to compute cut-off points for the mMDI.RESULTS: For both versions, local dependence was found between the three item pairs (loss of interest, lack of energy), (lack of self-confidence, feelings of guilt), and (concentration problems, feeling restless/slowed down). The mMDI displayed lower measurement error in the upper end of the scale and better item level fit for three of the four reformulated items compared to the MDI. For the MDI, 5.3% of the respondents gave improbable responses; the corresponding number was 3.4% for the mMDI. The mMDI displayed better fit to a one-factor model compared to the MDI. When comparing the correlation of the scales with the WHO-5 instrument, the corresponding AUROC estimates for the mMDI and MDI were found to be 0.93 (0.92; 0.96) and 0.91 (0.87; 0.94), respectively. The cut-off points for mild, moderate, and severe depression in the mMDI were found to be 17, 20, and 23, respectively.CONCLUSION: The proposed changes of the MDI are psychometrically sound upgrades of the original.

Background: We aimed to assess the psychometric properties of the ten-item Anxiety Symptom Scale (ASS) using Rasch analysis. Data from the Lolland-Falster Health Study (LOFUS) were used including ASS data for 16,137 persons aged 18–90 years. Methods: Fit to the Rasch model, ordering of response categories, dimensionality testing, test for differential item functioning, test for local dependency of items, and calculation of reliability were used to evaluate the psychometric characteristics of the ASS. Results: Ordered response categories were achieved for nine of ten items after modifying the original six-point scoring system into a five-point system. After adjustment of the sample size to 500 persons, the ASS fitted the Rasch Model (p = 0.051). Dimensionality testing supported combining the ten items into a total score. No significant differential item functioning was observed for sex, age group, and educational level. Items 1 and 9 and items 4 and 5 demonstrated indication of local dependency. Combining these two item pairs improved the fit of the ASS to the Rasch model. Limitations: The total ASS was poorly targeted for the LOFUS population as the majority of persons were located at the lower end of the construct. This poor alignment could explain the low reliability (PSI 0.49). Analyzing a balanced random sample of responders with high and low ASS scores demonstrated a sufficient PSI (0.81). Conclusions: Despite problems with the measurement structure, the ASS seems to be a promising instrument for measuring anxiety. However, it may prove more reliable for use in clinical samples of respondents.