Reliability and Validity of the Multidimensional Dyspnea Profile
Reliability and Validity of the Multidimensional Dyspnea Profile
The MDP was developed from existing instruments for pain and dyspnea and subsequently refined through laboratory work. It comprises 12 items (Fig 1): an immediate sensory intensity item, an immediate unpleasantness item, five items addressing sensory qualities (eg, tightness, muscle work), and five emotional response items (eg, frustration, anxiety). Sensory qualities of dyspnea were reduced from a list of 19 descriptors to five descriptor groups based on previous factor analysis in patients and laboratory use in healthy subjects and patients. The emotional response items were adapted from pain research.
(Enlarge Image)
Figure 1.
Intensity and unpleasantness scaling and listing of other items.
All items were measured on a rating scale of 0 to 10, with higher scores indicating greater intensity, unpleasantness, or distress. For overall intensity and unpleasantness, scaling words were used that accorded with the aspect being rated (ie, none, moderate, maximum, overall intensity vs neutral, annoying, unbearable unpleasantness). For the sensory quality items, subjects rated the intensity of the five descriptors, with 0 signifying "does not apply" and 10 signifying "as intense as I can imagine." Subjects were instructed to rate each emotional response item on a scale labeled "none" to the "most severe imaginable." See e-Appendix 1 for a detail script for first-time use.
This investigation used a longitudinal design that allowed serial determination of internal consistency, temporal stability, and responsiveness of the MDP to clinical change over time. We recruited individuals presenting to the ED with a breathing complaint. Patients with acute coronary syndromes or malignant neoplasms of the head, neck, thorax, or abdomen were excluded. The study had ethical approval from the University of New Mexico Human Research Review Committee (HRRC #07–062).
After informed consent in the ED, we administered the MDP (T1), followed by a second administration ~60 min later (T2), which served as a stability check (test-retest reliability), with the assumption that dyspnea might change but not resolve completely. At least 1 h after the second administration, the MDP was completed a third time (T3) to assess responsiveness to clinical change.
The MDP was administered a fourth and fifth time (T4, T5) at follow-up 4 to 6 weeks after discharge, with spirometry, pulse oximetry, and additional questionnaire data obtained for construct validity testing. Following completion of those additional measures, the MDP was administered again for the second time in the follow-up group (T5) as another stability check. Spirometry testing was done using a MicroLoop spirometer (CareFusion Corporation), according to guidelines established by the American Thoracic Society and European Respiratory Society, using National Health and Nutrition Examination Survey III predicted values.
Additional questionnaires included the Mini-Mental State Examination (MMSE), Brief Symptom Inventory (BSI), the modified Pulmonary Function Status Dyspnea Questionnaire (PFSDQ-M), and the Medical Research Council (MRC) dyspnea scale. The MMSE is a cognitive screening tool with scores ranging from 0 to 30; scores of ≥ 24 are normal. The BSI uses 18 items from the Symptom Checklist-90-R, having three subscales (somatization, depression, and anxiety) normed with T scores. The PFSDQ-M measures dyspnea and fatigue, with higher scores indicating greater intensity. Two items that ask about levels on most days and today were used. The MRC estimates dyspnea by grading breathing difficulty with daily activities. Scores range from grade 1 to 5, with satisfactory reliability and validity reported.
Analysis began with exploratory principal components analysis using a varimax rotation, using T1 data to determine the underlying factorial structure of the MDP. Details of the factor analysis procedures, factor selection, and item retentions are available in e-Appendix 1. The same analysis was run with data from T2 and T3 to assess the temporal stability of the MDP proposed domain structure. A separate factor analysis was not conducted at T4 because of the substantially smaller sample size.
After determining the proposed domain structure of the MDP through the factor analysis, we calculated Cronbach α for each domain at each administration and intraclass correlation coefficients (ICCs) for the domains and individual items across successive administrations. ICCs were used for test-retest reliability because unlike conventional correlation coefficients, ICCs account for error variance attributable to discrepancy over time. ICCs for domains were calculated using a two-way mixed-model analysis of variance for consistency of average measures and a two-way mixed model for absolute agreement for single items. Calculation of domain and item ICCs provided support for use of the stability of individual items or domains, depending on the proposed MDP use. Construct validity was assessed by correlations of the MDP domains with the additional questionnaire, spirometry, and pulse oximetry data obtained at T4. We used repeated-measures analysis of variance of the MDP domains and items using T1, T3, and T4 scores to determine responsiveness to change in patient condition. Analyses were conducted using SPSS version 18 (SPSS, Inc) statistical software.
Materials and Methods
Instrument Development and Content Validity
The MDP was developed from existing instruments for pain and dyspnea and subsequently refined through laboratory work. It comprises 12 items (Fig 1): an immediate sensory intensity item, an immediate unpleasantness item, five items addressing sensory qualities (eg, tightness, muscle work), and five emotional response items (eg, frustration, anxiety). Sensory qualities of dyspnea were reduced from a list of 19 descriptors to five descriptor groups based on previous factor analysis in patients and laboratory use in healthy subjects and patients. The emotional response items were adapted from pain research.
(Enlarge Image)
Figure 1.
Intensity and unpleasantness scaling and listing of other items.
All items were measured on a rating scale of 0 to 10, with higher scores indicating greater intensity, unpleasantness, or distress. For overall intensity and unpleasantness, scaling words were used that accorded with the aspect being rated (ie, none, moderate, maximum, overall intensity vs neutral, annoying, unbearable unpleasantness). For the sensory quality items, subjects rated the intensity of the five descriptors, with 0 signifying "does not apply" and 10 signifying "as intense as I can imagine." Subjects were instructed to rate each emotional response item on a scale labeled "none" to the "most severe imaginable." See e-Appendix 1 for a detail script for first-time use.
This investigation used a longitudinal design that allowed serial determination of internal consistency, temporal stability, and responsiveness of the MDP to clinical change over time. We recruited individuals presenting to the ED with a breathing complaint. Patients with acute coronary syndromes or malignant neoplasms of the head, neck, thorax, or abdomen were excluded. The study had ethical approval from the University of New Mexico Human Research Review Committee (HRRC #07–062).
After informed consent in the ED, we administered the MDP (T1), followed by a second administration ~60 min later (T2), which served as a stability check (test-retest reliability), with the assumption that dyspnea might change but not resolve completely. At least 1 h after the second administration, the MDP was completed a third time (T3) to assess responsiveness to clinical change.
The MDP was administered a fourth and fifth time (T4, T5) at follow-up 4 to 6 weeks after discharge, with spirometry, pulse oximetry, and additional questionnaire data obtained for construct validity testing. Following completion of those additional measures, the MDP was administered again for the second time in the follow-up group (T5) as another stability check. Spirometry testing was done using a MicroLoop spirometer (CareFusion Corporation), according to guidelines established by the American Thoracic Society and European Respiratory Society, using National Health and Nutrition Examination Survey III predicted values.
Additional questionnaires included the Mini-Mental State Examination (MMSE), Brief Symptom Inventory (BSI), the modified Pulmonary Function Status Dyspnea Questionnaire (PFSDQ-M), and the Medical Research Council (MRC) dyspnea scale. The MMSE is a cognitive screening tool with scores ranging from 0 to 30; scores of ≥ 24 are normal. The BSI uses 18 items from the Symptom Checklist-90-R, having three subscales (somatization, depression, and anxiety) normed with T scores. The PFSDQ-M measures dyspnea and fatigue, with higher scores indicating greater intensity. Two items that ask about levels on most days and today were used. The MRC estimates dyspnea by grading breathing difficulty with daily activities. Scores range from grade 1 to 5, with satisfactory reliability and validity reported.
Analysis
Analysis began with exploratory principal components analysis using a varimax rotation, using T1 data to determine the underlying factorial structure of the MDP. Details of the factor analysis procedures, factor selection, and item retentions are available in e-Appendix 1. The same analysis was run with data from T2 and T3 to assess the temporal stability of the MDP proposed domain structure. A separate factor analysis was not conducted at T4 because of the substantially smaller sample size.
After determining the proposed domain structure of the MDP through the factor analysis, we calculated Cronbach α for each domain at each administration and intraclass correlation coefficients (ICCs) for the domains and individual items across successive administrations. ICCs were used for test-retest reliability because unlike conventional correlation coefficients, ICCs account for error variance attributable to discrepancy over time. ICCs for domains were calculated using a two-way mixed-model analysis of variance for consistency of average measures and a two-way mixed model for absolute agreement for single items. Calculation of domain and item ICCs provided support for use of the stability of individual items or domains, depending on the proposed MDP use. Construct validity was assessed by correlations of the MDP domains with the additional questionnaire, spirometry, and pulse oximetry data obtained at T4. We used repeated-measures analysis of variance of the MDP domains and items using T1, T3, and T4 scores to determine responsiveness to change in patient condition. Analyses were conducted using SPSS version 18 (SPSS, Inc) statistical software.
Source...