Research in Gerontological Nursing

Instrument Development 

Development and Validation of the Dietary Sodium Reduction Self-Care Agency Scale

Pratsani Smith, PhD, RN; Kenneth D. Phillips, PhD, RN

Abstract

A scale did not exist for measuring the capability or self-care agency of lowering salt consumption in older adults with hypertension. Therefore, our objectives were to develop and validate the Dietary Sodium Reduction Self-Care Agency Scale (DSR-SCA Scale). A 24-item scale was developed and tested in 242 older adults with hypertension. Exploratory factor analysis using principal components extraction, Rasch analysis, and internal consistency reliability were used to evaluate the DSR-SCA Scale. Principal components extraction with Promax rotation was used. An 11-item DSR-SCA Scale with three factor loadings, which measure proficiency, persuasiveness, and resourcefulness, was finalized after it was found to meet the criteria of a minimal factor loading of 0.40, with eigenvalues of 2.20, 1.73, and 1.64, respectively. The Kaiser-Meyer-Olkin was 0.80, and Bartlett’s test was significant, χ2 (df = 55) 403.71, p < 0.0001. The measures accounted for 51% of the total variance. Item infit and outfit mean square ranged from 0.88 to 1.18 and the infit and outfit standardized mean square was −1.8 to 1.7. The 11-item scale demonstrated internal consistency with a Cronbach’s alpha coefficient of 0.73 for the total scale. The results showed that the DSR-SCA Scale consisted of three factors that have adequate construct validity and reliability to measure power components and enabling capability related to Orem’s self-care theory. This scale is brief, easy-to-complete, and useful for measuring salt reduction self-care agency in older adults with hypertension.

[Res Gerontol Nurs. 2013; 6(2):139–147.]

Abstract

A scale did not exist for measuring the capability or self-care agency of lowering salt consumption in older adults with hypertension. Therefore, our objectives were to develop and validate the Dietary Sodium Reduction Self-Care Agency Scale (DSR-SCA Scale). A 24-item scale was developed and tested in 242 older adults with hypertension. Exploratory factor analysis using principal components extraction, Rasch analysis, and internal consistency reliability were used to evaluate the DSR-SCA Scale. Principal components extraction with Promax rotation was used. An 11-item DSR-SCA Scale with three factor loadings, which measure proficiency, persuasiveness, and resourcefulness, was finalized after it was found to meet the criteria of a minimal factor loading of 0.40, with eigenvalues of 2.20, 1.73, and 1.64, respectively. The Kaiser-Meyer-Olkin was 0.80, and Bartlett’s test was significant, χ2 (df = 55) 403.71, p < 0.0001. The measures accounted for 51% of the total variance. Item infit and outfit mean square ranged from 0.88 to 1.18 and the infit and outfit standardized mean square was −1.8 to 1.7. The 11-item scale demonstrated internal consistency with a Cronbach’s alpha coefficient of 0.73 for the total scale. The results showed that the DSR-SCA Scale consisted of three factors that have adequate construct validity and reliability to measure power components and enabling capability related to Orem’s self-care theory. This scale is brief, easy-to-complete, and useful for measuring salt reduction self-care agency in older adults with hypertension.

[Res Gerontol Nurs. 2013; 6(2):139–147.]

Older adults with hypertension are often reported as having inconsistencies in performing self-care regarding salt reduction. Health care professionals have difficulty finding strategies to encourage them to engage in salt reduction self-care behavior, which is essential to promote health and prevent potentially life-threatening complications of high blood pressure, such as heart disease and stroke (Dahlöf, 2007; Dickinson & Havas, 2007; Mercado & Hilsabeck, 2005). Even with only minimal changes taking place with regard to blood pressure, chances of cardiovascular disease were found to be lowered by 25% with individuals in the sodium reduction intervention Trials of Hypertension Prevention follow-up study (Cook et al., 2007). Reduction of sodium intake to 1,256 mg per day over the lifetime can reduce the risk of hypertension by 20% and reduce mortality rates from congestive heart disease by 9% and from stroke by 14% (Dickinson & Havas, 2007). Moreover, sodium reduction helps prevent osteoporosis (Woo, Kwok, Leung, & Tang, 2009), improve pulmonary function and airway responsiveness in individuals with asthma (Mickleborough & Gotshall, 2004), and reduce the risk of gastric and nasopharyngeal carcinoma (Kurosawa, Kikuchi, Xu, & Inaba, 2006; Lijecnicki, 2009; Peleteiro, Lopes, Figueiredo, & Lunet, 2011). Sodium reduction is also cost effective in diminishing the economic and societal effects of hypertension (Mohan, Campbell, & Willis, 2009).

Background

Sodium Consumption

Reducing sodium intake seems to be very complicated. Only 79% of clients with hypertension reported reducing salt intake in their food (Viera, Kshirsagar, & Hinderliter, 2008). Thai individuals both with and without hypertension still consume more sodium than recommended. The majority (88%) of them have sodium consumption greater than 100 mmol per day (Sri-Ngernyuang, Wongjinda, & Aphichanakulchai, 2007), with an average of 7.76 g per day (Rujiwatthanakorn, 2004). For Western populations, excessive sodium consumption is due to processed foods and foods in restaurants (Anderson et al., 2010; Institute of Medicine, 2005; Zhou et al., 2003), which differs from Asian culinary styles, especially in Thailand. Success in the reduction of sodium intake in Western countries such as Finland, Ireland, and England was related the enforcement of law to control the amount of sodium added to processed foods, establishing salt-reduction initiatives, and raising consumer awareness (He & MacGregor, 2009; Webster, Dunford, Hawkes, & Neal, 2011). On the other hand, the major sources of dietary sodium consumed among Asian populations and in Thailand come from home-cooked food and its seasonings, such as soy sauce, soy paste, and fish sauce (Brown, Tzoulaki, Candeias, & Elliott, 2009; Ogawa et al., 2002; Ohta et al., 2005; World Health Organization, 2007). Studies in Asia related to salt reduction have focused on limiting salt and seasonings added to home-cooked food, distributing salt substitutes, and persuading the public to use less salt at home, rather than placing emphasis on policies designed to regulate the amount of sodium in processed foods distributed by food industries. (Anderson et al., 2010; China Salt Substitute Study Collaborative Group, 2007).

An individual approach to sodium reduction, by no means disregarding the universal approach, should be the focus in Thailand where differences in culinary styles, lifestyles, and accessibility to fundamental ingredients for daily cooking have been found among its populations, varying between the southern, central, northern, and northeastern regions. For example, one serving (250 g) of shrimp coconut soup contains 1,076 mg of sodium (Charoenkiatkul et al., 2003). This recipe is a well-known dish among people living in the central region of Thailand, but it is less likely to be consumed by people in the northern and northeastern regions. Northeasterners potentially prefer salty seasonings, which come from fermented freshwater fish, whereas southerners who have easy access to a large variety of seafood prefer salty seasonings such as shrimp paste, fish sauce, and oyster sauce. In addition, Thai people are accustomed to being able to find fresh ingredients all year in a tropical climate, making canned and processed foods less common in Thai households. Excessive salt is due to individual preference while cooking, rather than being added by food factories. Encouraging individuals to manage sodium consumption is still expected to have a substantial impact in Thailand.

Self-Care Agency

Self-care agency, the capability to deliberately perform action, is one of the most commonly used concepts of Orem’s self-care theory (Orem, 2001). In self-care theory, self-care agency is necessary for an individual to initiate behavior in caring for oneself, and a person is viewed as an agency that is anticipated to be able to make decisions to perform self-care behavior for maintaining health and well-being. Self-care agency involves three levels of capabilities: (a) foundational capabilities, which include perception, sensation, memory, and orientation; (b) power components, which are related to knowing and learning capabilities in seeking resources and making decisions to perform any actions; and (3) enabling capabilities, which address the capability of performing self-care operation (Gast et al., 1989; Orem, 2001). Self-care agency in each person is developed from childhood to old age and changes depending on internal and external environments; for example, health conditions, educability, mental development, life experiences, family and health care systems, resources, and sociocultural influences (Dodd & Dibble, 1993; Orem, 2001). People who have high self-care agency are more likely to use self-care behavior compared with those who perceive having less capabilities (Orem, 1995).

Self-care agency has gained attention and has been emphasized by health professionals in promoting self-care in various groups of patients (Evers, Isenberg, Philipsen, Senten, & Brouns, 1993; Herber, Schnepp, & Rieger, 2008; Zrínyi & Zékányné, 2007). Older adults whose self-care agency decreases with age (Soderhamn, Lindencrona, & Ek, 2000) should be assessed for their competence in performing certain health behaviors, including managing sodium consumption. The authors believe older adults with hypertension would benefit if a salt reduction self-care agency assessment tool were available for health care providers to investigate and measure older adults’ perceptions of their abilities to lower salt consumption.

For the literature review of MEDLINE, CINAHL, PsycINFO, Web of Science, ERIC, Education Full Text, Scirus, and Google Scholar (1990–2009), various potential key words were used, such as sodium reduction scale, salt reduction scale, sodium restriction questionnaire, and sodium intake instruments. Several questionnaires were found with some limitations, including those in languages other than Thai and English and those focusing on facilitators and barriers of salt adherence that did not directly assess an individual’s capability (Bentley, Lennie, Biddle, Chung, & Moser, 2009; Cornélio et al., 2009). Thus, an instrument did not exist to help health care professionals gain insight into and better understand the sodium-reduction capabilities of older adults with hypertension who potentially have excessive salt intake. Consequently, the purpose of this research was to develop and validate an instrument to specifically measure dietary salt reduction self-care agency of older adults with hypertension. It is our hope that the instrument will help measure their determination and adequacy of self-care agency to perform self-care.

Method

Item Construction and Validity Testing

Based on the literature review, a pool of 24 items was developed in English, using a 4-point Likert response scale ranging from 1 (strongly disagree) to 4 (strongly agree). The total score ranges from 24 to 96, with a higher score indicating better self-care agency in lowering salt consumption. The research team screened, discussed, and evaluated 65 items, which encompassed the three levels of capabilities in the pool: foundational capabilities, power components, and enabling capabilities. Twenty-four items were chosen based on their appropriateness to older adults with hypertension in northern Thailand, as well as relevance to salt reduction self-care agency.

A panel of four content experts, which included both Thai and U.S. nursing researchers who are experts in sodium reduction, hypertension in older adults, and self-care agency, were asked to review and rate the 24-item scale for its relevance, comprehension, and clarity. According to the expert review, no item was suggested for deletion. Disparateness toward some items existed between experts, resulting in the research team taking their suggestions and then revising those items until the content validity of the total scale was 0.80. The scale went through a process of back-translation where it was first translated into Thai by five bilingual individuals before being translated back into English by another set of five bilingual individuals and found to be consistent among language experts. Following this process, 10 Thai older adults were asked to complete the questionnaire in Thai to test it for face validity and measure the readability of the Thai version of this instrument. Encouragement was given to the older adults for sharing, rating, and commenting on the Thai version of the instrument and individual items within it through oral or written feedback. The feedback provided was valuable during scale revision as it helped verify the instrument’s clarity and understandability.

Data Collection

Data for this cross-sectional study were collected between December 2009 and January 2010. A total of 242 older patients with hypertension at the hypertensive clinic in a tertiary hospital located in the northern region of Thailand participated in this study. The participants were recruited based on the criteria that they were age 60 or older, diagnosed with hypertension for at least 1 year, and had been undergoing treatment through lifestyle changes and/or anti-hypertensive medications. Convenience sampling on a voluntary basis was applied with older adults with hypertension who had clinic appointments in the outpatient department. Exclusions were made for the study for those patients who had a medical history that included psychiatric illnesses such as schizophrenia, bipolar disorder, and severe dementia.

Upon receiving approval from the Institutional Review Board in the United States and the Research Ethical Review Committee in Thailand, including the granting of allowance for data collection from the hospital director located in the Chiangrai province, the first author met with hospital staff at an outpatient unit to begin seeking potential participants. Those patients who chose to participate, as well as those who did not, remained anonymous to prevent the hospital staff from knowing who made the decision to participate in the study. All participants joined on a voluntary basis and were asked to sign informed consent forms. Whether the potential recruits decided to join the study or not would not affect the benefits, services, or any other resources to which they were otherwise entitled, and confidentiality was further assured. The participants were asked to answer the self-report DSR-SCA Scale and provide information such as age, sex, educational level, marital status, presence of other chronic diseases, cooking ability, family food providers, and family culinary styles. After reviewing the instructions for completing the questionnaire, participants could choose whether to complete it while waiting for their physician appointment or to complete it at home and return it to the research team by postal mail using a provided stamped, addressed envelope. Most of the participants completed the questionnaires at the hospital; only 3 older adults returned them via postal mail. Anonymity for participating patients was maintained throughout the entire duration of the study, and only data accompanied by signed consent forms were used during data analysis procedures.

Data Analysis

To examine the psychometric properties of the DSRSCA Scale, exploratory factor analysis (EFA) in SPSS version 17.0 and the Rasch Measurement Model with the WINSTEPS program version 3.69.1.14 (Linacre, 2010) were used. Participants’ characteristics were descriptively analyzed using mean, standard deviation, and percentage. EFA with principal components extraction (PCE) and Promax rotation was used to evaluate the strength of each item with the theoretical concept and the DSR-SCA Scale. The minimal factor loading was set at 0.40 to retain component weights (Devellis, 2003; Polit, 2010). All factors with eigenvalues greater than 1 and a scree plot with the number of data points above the “elbow” were retained. The Kaiser-Meyer-Olkin was tested to examine sampling adequacy and Bartlett’s test of sphericity at p < 0.05 was determined to be statistically significant (Costello & Osborne, 2005; Pett, Lackey, & Sullivan, 2003).

Rasch analysis, a form of Item Response Theory used in the assessment of health outcome measures and evaluation of instruments (Kopec, 2000; McHorney, 1997), was also used to analyze rating scale, unidimensionality, and item difficulty. Rasch analysis is useful when researchers aim to test whether items measure a unidimensional construct and how all of the items fit with that construct. Hypothesized item hierarchy with empirical hierarchy of item calibrations can also be confirmed by Rasch analysis (Wolfe & Smith, 2007a, 2007b). The rating scale was at least 10 counts per each response (Linacre, 1999). Monotonically increasing of the structure calibration was accepted to be within 1.40 to 5.0 logits (Linacre, 1999). The scale unidimensionality with the infit and outfit mean squares (MNSQ) were limited between 0.75 to 1.30 (Bond & Fox, 2007), along with the infit and outfit standardized mean square (ZSTD) being accepted at values between −2.0 to 2.0 (Bond & Fox, 2007; Chen, Bode, Granger, & Heinemann, 2005). The Cronbach’s alpha coefficient was 0.7, indicating it to be an acceptable reliability coefficient (Nunnally & Berstein, 1994).

Results

Characteristics of the Study Participants

A total of 242 older adults with hypertension were enrolled in this study, with 126 (51%) women and 116 (49%) men. Their ages ranged from 60 to 90 (mean age = 68.95, SD = 7.10 years). Study participants were predominately married (65%), completed primary school or lower (93%), preferred to consume northern Thai food and were still active in cooking (88%), and rated their cooking skill as good (66%). Most (90%) of the participants still lived with their spouse and/or child. Family food providers included oneself (39%), spouses (31%), children (21%), and others (9%). The majority (91%) of them needed both anti-hypertensive medication and lifestyle modifications. Less than half (42%) had other chronic diseases such as diabetes mellitus, arthritis, chronic pulmonary disease, and heart disease. A few of them also reported having food allergies and limitations in eating and chewing food.

Factor Analysis and Rasch Analysis of the 24-item DSR-SCA Scale

The 24-item scale was analyzed by the principal components factor analysis without rotation. Seven factors were revealed, accounting for 56% of the variance. Eigenvalues of factors 1 to 7 were 5.58, 1.53, 1.40, 1.36, 1.28, 1.11, and 1.07, respectively. The Kaiser-Meyer-Olkin of this scale was 0.81, and Bartlett’s test was significant, χ2 (df = 276) 1235.00, p < 0.0001. All items had a loading factor greater than 0.40 for certain factors. Twenty items loaded for factor 1. Three, two, two, two, one, and one item(s) loaded for factors 2 to 7, respectively. After that, Promax rotation was challenged. The seven factors were extracted, with 56% of total variance explained. The Cronbach’s alpha coefficient of this scale was 0.84.

The Rasch analysis of this scale was also performed. The rating scale, observed count, average measures, fit statistics, and step measures (structure calibration) were displayed. Four rating scale category counts met the criteria that they should have at least 10 observed counts, which were respectively 13, 27, 178, and 23 for categories 1 to 4. The step measures or structure calibration between step 2 to step 3 were disordered, demonstrating that step 2 was the least likely response to be observed. The score of infit and outfit MNSQ ranged from 0.82 to 1.79 and 0.72 to 1.89, respectively. The score of infit and outfit ZSTD ranged from −1.5 to 7.9 and −2.2 to 8.5, respectively. All items, except item 13, had infit MNSQ within the range at 0.75 to 1.30. The majority of items had infit and outfit ZSTD scores within the limit at ±2 (Table 1). Items 6, 16, 17, and 22 were the easiest to endorse, and item 13 was the most difficult to endorse.

Rasch Analysis for Fit Statistic of the 24-Item DSR-SCA Scale

Table 1: Rasch Analysis for Fit Statistic of the 24-Item DSR-SCA Scale

Finalized Scale

Based on psychometric properties gained after factor analysis and Rasch analysis, including factor loading, scree plot, eigenvalues, structure calibration, and fit statistics, six items—9, 11, 12, 13, 14, and 20—were deleted. The 18-item scale was reanalyzed with factor analysis, Rasch analysis, and reliability. After applying many solutions to solve the problems of cross loading and inadequacy of items in some factors, the research team considered that seven items (2, 3, 6, 16, 19, 22, and 24) should be further removed (Pett et al., 2003). The 11-item DSR-SCA Scale with three factor solutions was finalized. All items had factor loadings greater than 0.40 and ranges from 0.51 to 0.82. The eigenvalues were 2.20, 1.73, and 1.64. The factors accounted for 51% of the variance—20%, 16%, and 15% for factors 1 to 3, respectively. The Kaiser-Meyer-Olkin was 0.80, and Bartlett’s test was significant, χ2 (df = 55) 403.71, p < 0.0001). These three factors were judged to represent proficiency, persuasiveness, and resourcefulness, respectively.

The rating category of the 11-item DSR-SCA Scale was also examined. All category counts, average measures, category fit statistics, and structural calibration were acceptable (Table 2). The step measures were gradually increased compared with the 24-item scale, especially category 2, which was more probable to be endorsed. For unidimensionality, every item had MNSQ and ZSTD scores within the limit. The infit and outfit MNSQ ranged from 0.88 to 1.18 (mean = 0.99, SD = 0.08) and 0.86 to 1.13 (mean = 0.94, SD = 0.08), respectively. The infit and outfit ZSTD score ranged from −1.3 to 1.7 (mean = −0.10, SD = 0.80) and −1.8 to 1.2 (mean = −0.60, SD = 0.80), respectively. The variable map or item difficulty of the 11-item DSR-SCA Scale showed that item 1 was the most difficult to endorse, whereas items 16 and 17 were the easiest to endorse.

Rating Scale Analysis for the Four Categories of the 11-Item DSR-SCA Scale

Table 2: Rating Scale Analysis for the Four Categories of the 11-Item DSR-SCA Scale

Regarding reliability, the Cronbach’s alpha coefficient was 0.73 for the total scale and 0.66, 0.60, and 0.60 for proficiency, persuasiveness, and resourcefulness subscales, sequentially. The psychometrics properties of the finalized scale are presented in Table 3.

Factor Analysis with Promax Rotation, Fit Statistics, and Cronbach’s Alpha Coefficients of the 11-Item DSR-SCA Scale

Table 3: Factor Analysis with Promax Rotation, Fit Statistics, and Cronbach’s Alpha Coefficients of the 11-Item DSR-SCA Scale

Discussion

In this article, three constructs of older adults’ with hypertension self-care agency in lowering salt consumption were operationalized and presented in the first developed DSR-SCA Scale. The development of this scale began with item generation by literature review and team discussion, item refinement, scale testing, and scale revision. The psychometric evaluation of this scale demonstrated validity, reliability, rating response, unidimensionality, and item difficulty when subjected to principal components factor analysis with Promax rotation, reliability testing (Cronbach’s alpha coefficient), and Rasch analysis. The face validity of this scale was also evaluated in cultural appropriateness for setting and samples. Following Stevens (2009), this study used the rule of thumb that adequacy of sample size recruited from the general populations should be 5 to 10 participants per variable. Additionally, findings from this study were congruent with the concept of self-care agency. According to Orem (1995), self-care agency is a deliberate action in which a person tries to foresee the result, as well as investigate, reflect, and judge the choices with thoughtfulness. Individuals, families, or groups have different stages in development of self-care agency. In addition, a person’s willingness to pursue and engage in self-care action involves internal or external necessitate conditions including foundational capabilities, power components, and enabling capabilities (Gast et al., 1989).

From the findings of this study, the researchers considered that three components of the DSR-SCA Scale—proficiency, persuasiveness, and resourcefulness—reflect two of three important capabilities of self-care agency: power components and enabling capabilities. More specifically, the capability of older adults with hypertension can be predicted by three capabilities related to self-care agency. The first five items, categorized as proficiency, and another three items, grouped as resourcefulness, are potentially appropriate to measure power components. The three other items, categorized as persuasiveness, were close to enabling capabilities. The self-care agency of older adults with hypertension to lower salt consumption has not been widely investigated or understood. The DSR-SCA Scale has provided the necessary components of those capabilities in assessment of proficiency, persuasiveness, and resourcefulness, which hopefully is useful for health care providers to gain insight and be able to understand, screen, plan, and implement appropriate strategies for these patients.

Limitations

Although the sample size was acceptable, a limitation of this scale that should be mentioned is the convenience sampling of populations, resulting in the samples being dominated by active and social older adults with hypertension. Although the sample was older adults with hypertension, it might not be the most representative of older adults who are more vulnerable. Further study of the instrument in a wider range of samples with various comorbid conditions and those who are less independent, as well as replications of this scale in similar samples for validation, are suggested for future research.

Conclusion

The 11-item DSR-SCA Scale is a self-report instrument that can be used to reflect the perceptions of older adults, which may not fully translate into action, toward their capability to reduce sodium intake. However, heterogeneous samples or those older adults who have low physical activity, performance, and socialization need further investigation in applying this scale. Replicating the study and applying the confirmatory factor analysis in similar samples to test the factor structure and other psychometric properties would also be recommended.

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Rasch Analysis for Fit Statistic of the 24-Item DSR-SCA Scale

Fit Statistics
Infit Outfit
Item MNSQ ZSTD MNSQ ZSTD
1. I can ask my family members to cook a low-salt diet for me if I cannot do it by myself. 0.88 −1.0 0.80 −1.5
2. When I intend to cook low-salt diet, I can do it by myself. 0.91 −0.7 0.91 −0.8
3. I try to decrease an amount of salt in my food. 0.94 −0.6 0.92 −0.7
4. I can find ways to control salt in my food. 0.99 −0.1 0.89 −1.0
5. I can motivate myself to reduce salt in my food. 0.96 −0.4 0.93 −0.6
6. I apply my past successful experience to reducing salt in food. 1.02 0.2 1.00 0.0
7. I can convince my family members to eat a low-salt diet though they do not have high blood pressure. 0.88 −1.3 0.86 −1.5
8. I can take care of myself to control salt in my food. 1.00 0.1 0.90 0.9
9. I ask family members to cook low-salt diet for me when I am unable to by myself. 1.11 1.2 1.25 2.5
10. I know the people who can advise me regarding reduction of dietary salt. 1.03 0.3 0.97 0.3
11. I care for dietary salt reduction. 0.82 −1.5 0.72 −2.2
12. I can consult with health care providers to help me reduce salt in diet. 0.87 −1.2 0.84 −1.5
13. I have enough power to tell my family members to cook a low-salt diet for me. 1.79 7.9 1.89 8.5
14. I can evaluate dietary salt reduction every day. 0.99 −0.1 0.91 −0.9
15. I can cook a low-salt diet for my family members. 0.96 −0.3 0.91 −0.7
16. I try to eat a low-salt diet every day. 0.96 −0.3 0.94 −0.6
17. I know the amount of salt in my food. 0.94 −0.5 0.89 −1.0
18. I can share information about dietary salt reduction with other people. 0.92 −0.9 0.88 −1.2
19. I update my salt-reduction information. 0.91 −0.9 0.89 −1.2
20. I know resources of information about dietary salt reduction. 1.04 0.4 0.94 0.5
21. I have willpower to control myself to eat a low-salt diet. 0.89 −1.0 0.83 −1.6
22. I intend to control the amount of salt in my food. 0.98 −0.2 0.90 −0.8
23. I think limiting a salty diet is easy. 0.95 −0.5 0.92 −0.9
24. I think I am not too old to change myself to eat a low-salt diet. 1.18 1.8 1.33 3.1

Rating Scale Analysis for the Four Categories of the 11-Item DSR-SCA Scale

Category Label Observed Score (%) Observed Average Outfit MNSQ Structural Calibration Category Name
1 10 (4%) −0.90 0.60 None Strongly disagree
2 59 (24%) 0.22 0.90 −2.26 Disagree
3 135 (56%) 1.26 0.77 −0.41 Agree
4 37 (15%) 2.00 1.08 2.67 Strongly agree

Factor Analysis with Promax Rotation, Fit Statistics, and Cronbach’s Alpha Coefficients of the 11-Item DSR-SCA Scale

Fit Statistics
Three-Factor Solution Infit Outfit
Item (Number on the 24-Item Scale) Cronbach’s Alpha h2 Factor 1 Factor 2 Factor 3 MNSQ ZSTD MNSQ ZSTD
PROFICIENCY 0.66
1. (4) I can find ways to control salt in my food. 0.73 0.39 0.61 0.96 −0.3 0.88 −0.8
2. (15) I can cook a low-salt diet for my family members. 0.74 0.29 0.51 1.03 0.3 0.94 −0.5
3. (17) I know the amount of salt in my food. 0.73 0.56 0.65 0.97 −0.3 0.93 −0.7
4. (21) I have willpower to control myself to eat a low-salt diet. 0.72 0.67 0.63 0.88 −1.3 0.86 −1.5
5. (23) I think limiting a salty diet is easy. 0.73 0.52 0.72 1.08 0.7 0.98 −0.1
PERSUASIVENESS 0.60
6. (1) I can ask my family members to cook a low-salt diet for me if I cannot do it by myself. 0.73 0.58 0.73 0.98 −0.1 0.94 −0.6
7. (8) I can take care of myself to control salt in my food. 0.74 0.67 0.81 0.89 −1.0 0.81 −1.8
8. (18) I can share information about dietary salt reduction with other people. 0.73 0.38 0.52 1.00 0.0 0.96 −0.4
RESOURCEFULNESS 0.60
9. (5) I can motivate myself to reduce salt in my food. 0.73 0.52 0.69 1.18 1.7 1.13 1.2
10. (7) I can convince my family members to eat a low-salt diet though they do not have high blood pressure. 0.72 0.53 0.60 1.05 0.4 1.00 0.0
11. (10) I know the people who can advise me regarding reduction of dietary salt. 0.75 0.67 0.82 0.93 −0.6 0.88 −1.0
Authors

Dr. Smith is Nursing Instructor, Boromarajonani College of Nursing, Bangkok, Thailand, and Dr. Phillips is Professor and Associate Dean for Research and Evaluation, The University of Tennessee, College of Nursing, Knoxville, Tennessee.

The authors have disclosed no potential conflicts of interest, financial or otherwise. The authors acknowledge all four nursing professors who provided expert assistance for this project, as well as the bilingual individuals who performed translation and back-translation. In addition, the authors thank all participants for their willingness to participate in the study and the hospital for allowing data collection, as well as providing staff support while collecting the data.

Address correspondence to Pratsani Smith, PhD, RN, Nursing Instructor, Boromarajonani College of Nursing, 2/1 Phayathai Road, Rajthevi, Bangkok, 10400 Thailand; e-mail: pratsanii@gmail.com.

Received: September 17, 2011
Accepted: September 19, 2012
Posted Online: January 17, 2013

10.3928/19404921-20130108-01

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