Introduction

Background

Amid a constant influx of health information in modern society, the ability to find, understand, and utilize health information necessary for oneself is one of the basic abilities required for individuals to maintain and promote their health. Health literacy refers to important knowledge and skills needed for individuals to manage their health, prevent diseases, and perform health promotion activities [1]. It is a complex concept that goes beyond simply understanding information and includes the ability to critically analyze information and utilize it in the process of social interactions [2]. Nutbeam [3] explained health literacy by dividing the concept into three subconcepts: functional, interactive, and critical health literacy. According to Nutbeam [3], functional health literacy is the ability to understand and utilize general health information, interactive health literacy is the ability to utilize health information in the social context, and critical health literacy is the ability to critically analyze the effectiveness of heath information and utilize it. According to the definition of health literacy presented by Nutbeam, health literacy can be regarded as an essential ability for community residents to manage and promote their health in the research and practice of community nursing. In other words, the functional aspect of health literacy enables basic personal health management in daily life, the interactive aspect allows people to solve health problems together within the community, and the critical aspect helps people to evaluate the quality of information and make appropriate decisions [3]. Therefore, in community nursing, it is considered very important for the health promotion of residents to comprehensively evaluate and strengthen the above-mentioned three aspects of health literacy.

This health literacy is closely related to the health status of individuals. A lack of health literacy may lead to not performing disease prevention behaviors [4] or not practicing health promotion behaviors [5]. In addition, inadequate health literacy prevents individuals from properly judging the quality of health information, which may result in higher medical expenses [6,7], and low health literacy also negatively affects hospital readmission rates [7,8] and mortality rates [9]. As described above, adequate health literacy is essential for individuals, but previous studies to evaluate health literacy in the general population using the European Health Literacy Survey (HLS-EU-Q47) showed that the proportion of people with inadequate or poor health literacy was 21.4% in Korea [10], 47.6% in Europe [11], and a very high percentage of 85.4% in Japan [12], showing that inadequate health literacy is a common problem in Korea and abroad. These results suggest that education and interventions are required to improve health literacy, and for this purpose, it is necessary as a prior step to find or develop a valid and reliable assessment tool that can accurately assess the health literacy of participants.

Currently, various tools have been developed and used to assess health literacy, but these existing tools have several problems. For example, HLS-EU-Q47 [13] allows the multidimensional assessment across four domains of processing health information (finding, understanding, judging, and applying health information) and three domains of health (health management, disease prevention, and health promotion). However, since it contains 47 questions, it has a disadvantage in that it gives a burden to respondents due to a large number of questions and requires a long assessment time.

The Korean Health Literacy Assessment Tool (KHLAT) [14] is a tool focused on measuring the understanding of medical terms, but for this tool, only the rates of understanding and comprehension for items and the reliability coefficient for internal consistency have been presented, and its validity has not been sufficiently verified. Moreover, since it consists of 66 items, it also has the disadvantage that it contains a large number of items. The Test of Functional Health Literacy in Adults (TOFHLA) [15] is divided into math and comprehension domains, but it also has the disadvantage of having a large number of questions since it contains 67 questions. The Newest Vital Sign (NVS) [16,17] is a simple tool that consists of 6 items, but it measures only the decision-making ability on health behaviors, based on the responses to the questions about calorie, the amount of food, nutrients, and allergy that the respondents are asked to answer by using the nutrition facts table of ice cream given with the questions. Chun et al. [18] presented a Korean version of a 16-item health literacy assessment tool developed by Chew et al. [19] by translating, modifying, and supplementing the original version. The tool developed by Chun et al. [18] is a 12-item health literacy assessment tool for older adults. It has the advantage that it can be used to assess understanding about the use of medical services unlike the REALM tool about medical terms or TOFHLA or NVS, which is focused on numerical calculations, but it has limitations on its use since it was validated only for older adults aged 60 or older.

As described above, each of the existing tools has different strengths, but since they contain a large number of items, they give a burden to respondents, and require a relatively long time for assessment, so they are not suitable as a tool for a large-scale community survey or a survey of the general population in the community because they are designed to be used for specific age groups or people with particular cultural backgrounds. Moreover, the majority of existing tools have limitations in that they do not sufficiently reflect various aspects of health literacy since they generally approach health literacy as a single-dimensional concept. Therefore, there is a need for a simple but comprehensive health literacy assessment tool that can be effectively utilized in the field of community nursing and public health.

The Health Literacy Assessment Tool 8 (HLAT-8) developed by Abel et al. [20] consists of 8 items, and is a simple but comprehensive assessment tool for health literacy. In a meta-analysis study [21], it was evaluated as the tool with the highest construct validity among the 29 health literacy assessment tools selected and analyzed in the study.

HLAT-8 was developed based on the definition of health literacy presented by Nutbeam [3], and this tool can effectively assess how community residents understand and utilize health information in their daily life since it can assess various aspects of health literacy, such as understanding health information, finding health information, and interactions related to health information. In addition, HLAT-8 has also been translated in Brazil [22] and China [23]. These translated versions were made through modification and supplementation to reflect the cultural characteristics of each country, and the reliability and validity of them have been verified.

Therefore, this study aimed to develop a Korean-translated version of HLAT-8, and verify the reliability and validity of the Korean version in order to utilize it as a tool suitable for research in community nursing and public health in Korea.

Methods

Study design

This study is a methodological study to make a Korean-translated version of HLAT-8 developed by Abel et al. [20], and verify the validity and reliability of the Korean version by applying it to Korean adults.

Participants

The participants of this study were a total of 220 adults aged 19 to 64, and they were selected by convenience sampling among people who visited the outpatient clinic of a university hospital or a forest bathing site in D City and current students or workers of E University in D City. The same size of this study was determined based on a previous study’s suggestion that the minimum sample size required for confirmative factor analysis to test construct validity is 150 people [24]. In consideration of the dropout rate, 220 copies of the questionnaire were distributed and collected, and 210 copies were included in the analysis excluding 10 copies with a lot of missing data. Test-retest reliability was measured using data collected from 20 people selected by convenience sampling, based on the minimum sample size of 10 people required for reliability analysis for stability [25].

Measures

1. Health literacy assessment tool

HLAT-8 developed by Abel et al. [20] is a simple questionnaire to measure health literacy in terms of individuals’ ability to deal with health problems in daily life, and it was developed using large-scale nationwide data of 8,349 young adults aged 18 to 25 in Switzerland. This instrument consists of 4 subdomains, each with 2 items, and thus contains 8 items in total. The 4 subdomains of health literary are the two areas of the functional aspect, the critical aspect, and the interactive aspect. More specifically, the functional aspect is divided into the ability to understand health information and the ability to find health information, the critical aspect is related to judging whether health information is accurate or useful, and the interactive aspect includes interactions such as answering questions and giving advice in the relationships with the family and friends. In this tool, 5 items (questions 1, 2, 5, 6, and 7) are rated on a 5-point Likert scale, but 3 items (questions 3, 4, and 8) are assessed on a 4-point Likert scale, and response options are different depending on questions. In addition, this instrument includes ‘not applicable’ as a response option, and if the response is ‘not applicable (=0 points)’, it is treated as a missing value. The total scores range from 8 to 37 points, and higher scores indicate higher levels of health literacy. Regarding the reliability of the instrument, Cronbach’s α was reported as .64 by the developer of the tool.

2. Self-care assessment tool

To assess convergent validity, a Korean version of the Self-As Carer Inventory (SCI) was used. The SCI is a 40-item self-care competency assessment tool developed by Geden & Taylor [26]. The Korean version used in this study consists of 34 items, and was developed by H-S So [27] through the translation and modification of the original version. The construct validity of the Korean version was verified by So [27]. This Korean version of SCI consists of 6 subdomains: cognitive aspects of self-care (11 items), physical skills (9 items), decision-making and judgement processes (5 items), information-seeking behaviors (4 items), perception of self-monitoring (2 items), and attention to self-management (3 items). Each item is rated on a 6-poing scale ranging from 1 point (=‘Strongly disagree’) to 6 points (=‘Strongly agree’). Higher scores indicated higher levels of self-care competency. Regarding the reliability of the original version of SCI, Cronbach’s α was reported as .96 by Geden & Taylor [26] and for the Korean version, Cronbach’s α was reported as .92 by So [27]. For Cronbach’s α of each subdomain, the Cronbach’s α values were .812 for cognitive aspects, .842 for physical skills, .871 for decision-making and judgement processes, .852 for information-seeking behavior, .864 for perception of self-regulation, and .873 for attention to self-management. In this study, Cronbach’s α for the total items was .94.

4. Procedure

This study was conducted in the following three steps: 1. translation of the scale and establishment of content validity; 2. preliminary survey; 3. scale validation.

1. Stage of translation of the scale and establishment of content validity

In this study, translation of HLAT-8 was conducted after receiving permission for its use from the developer of the tool. The translation of HLAT-8 was carried out by the forward-backward translation method, which is the method of translation and reverse translation. Initially, translation of the tool into Korean was conducted by a Korean-English bilingual speaker from an English-speaking country who had a bachelor’s degree in nursing. Then, researchers had a meeting to revise and supplement the translation through a review regarding the clarity of the content of the translated version and the appropriateness of the expressions and words used. Afterwards, for reverse translation, a nursing professor who was fluent in both English and Korean was requested to back-translate the items translated into Korean. In this process, independence from each other between the translator and the back-translator was maintained. As a next step, a nursing professor and the back-translator together compared the back-translated version with the original version, and discussed and checked whether there were any differences in meaning between the two versions or any problems such as the ambiguity of expressions and distortions due to cultural differences. In this process, it was considered difficult to understand the term ‘information brochures on health issues’, so it was revised to ‘pamphlets on heath information’, and other items were not revised.

Regarding the response option of ‘not applicable’ included in the original tool, there is a problem that if a respondent chooses ‘not applicable’, the response is treated as a missing value and excluded from analysis. Moreover, respondents may be confused regarding whether it is appropriate to regard ‘not applicable’ as a missing value and exclude it from analysis when a respondent chooses the response, so they may misunderstand the questions or give inaccurate responses. In consideration of these problems, it was agreed via email with the author of the original tool that it is considered appropriate to delete the response option ‘not applicable.’ As a result, the final Korean-translated version was completed.

The content validity of the Korean-translated version was verified by checking the content validity index (CVI), and was verified by a total of six experts: four nursing professors, a public nursing official with 10 years or more of work experience, and a nurse with 10 years or more of clinical experience. Content validity was assessed on a scale from ‘Very much’ (4 points) to ‘Not at all’ (1 point) regarding whether the items of the tool were appropriate for measuring health literacy and whether the respondents had no difficulty reading and understanding the items. As a result, the item content validity index (Item-CVI) values of all the eight items were 1.0, and the scale content validity index (Scale-CVI) was also found to be 1.0.

2. Stage of the preliminary survey

To check the Korean version of 8-item Health Literacy Assessment Tool (K-HLAT-8) in terms of the level of understanding of the questions and easiness or difficulty in responding to them, a preliminary survey was conducted among 10 adults, who consisted of current students or workers of * University in * City. The survey was conducted after explaining the purpose of the study to the participants and receiving their permission. The mean age of the participants was 32.4 years, and they included 3 males (30.0%) and 7 females (70.0%). Regarding the education level, the participants consisted of 2 high school graduates (20.0%), 2 people with the education level of college or higher in health-related fields (20.0%), and 6 people with the education level of college or higher in non-health-related fields (60.0%). The results of the preliminary survey showed that all the questions were easy to understand and not difficult to respond, so the final translated version was completed without making any revisions.

3. Stage of scale validation

The validity of K-HLAT-8 was verified by assessing construct validity and convergent validity. Construct validity was verified by confirmatory factor analysis [CFA] and calculating the item convergent and discriminant validity values. Since HLAT-8 has sub-concepts derived through the verification of construct validity at the time of the development of the original version, this study conducted confirmatory factor analysis to present structural equations for each sub-category and the items of the original tool [28]. The item convergent validity of the tool was verified firstly by estimating the factor loadings, secondly by calculating the Average Variance Extracted (AVE) value, and thirdly by computing the Construct Reliability (C.R.) value. The item discriminant validity was verified by the following two methods. Firstly, item discriminant validity was verified by computing the AVE value, based on the following criterion: ‘If the AVE value is greater than the square of the correlation coefficient, discriminant validity can be considered to be secured’ [29], and Secondly, discriminant validity was verified by the estimation of the standard error confident interval based on the criterion that ‘the range of values obtained by adding or subtracting the standard error × 2 from the correlation coefficient value must not include 1.’ [29]. The convergent validity of the tool (scale convergent validity) was verified by examining the correlation between the scores of the K-HLAT-8 and the Self-As Carer Inventory (SCI). Reliability was verified by assessing internal consistency reliability (Cronbach’s α) and test-retest reliability. Test-retest reliability was assessed by performing the retest with 20 adults selected from the participants of the first survey by convenience sampling. The 20 participants were people who agreed to participate in the second survey after explaining the second meeting to the participants at the time of the first data collection. The retest was conducted two weeks after the first data collection.

Data analysis

The general characteristics of the subjects were analyzed using descriptive statistics. For item analysis, the mean, standard deviation, and skewness and kurtosis of each item and each factor, the corrected item-total correlation coefficient (ITC), and the ceiling and floor effects were computed. Skewness and kurtosis values were analyzed to assess normality, and they were evaluated based on the criterion that normality is satisfied when the skewness and kurtosis values are less than the reference value ±1.97 at a significance level of 5% [29]. The corrected item-total correlation coefficient (ITC) is a value for evaluating the correlation between individual items and the total items, and it is evaluated as showing a low correlation when the ITC value is less than [30,31]. The ceiling effect and floor effect are the percentage frequencies (%) of the lowest and highest scores of items, respectively, and they are considered appropriate if they are less than 30% [32]. Construct validity was assessed by confirmatory factor analysis (CFA). In assessing model fit, for absolute model fit indices, it was examined whether they met the following criteria: p value of .05 or higher for Chi-square(χ²); less than 3 for Normed χ²it; .05~less than .80 for Root Mean Square Residual (RMR) and Root Mean Square Error of Approximation (RMSEA); .90 or higher for Goodness of Fit Index (GFI). For incremental fit indices, it was checked whether Comparative Fit Index (CFI) and Incremental Fit Index (IFI) are .90 or higher as the acceptable thresholds for the indices [29]. Item convergent validity was verified using the following criteria: a standardized factor loading of .50 or higher, a construct reliability (C.R.) coefficient of .70 or higher, and the average variance extracted (AVE) of .50 or higher [29]. Item discriminant validity was assessed by examining whether there is a low correlation between the subfactors and thus whether the factors are independent, and item discriminant validity was verified by confirming that the two conditions were met. More specifically, firstly, discriminant validity was verified based on the criterion that ‘if all AVE values are greater than the square of the correlation coefficient, discriminant validity is considered to be secured [29]. Secondly, discriminant validity was also verified based on the second criterion that ‘the range of values obtained by adding or subtracting the standard error multiplied by 2 from the correlation coefficient value must not include 1’ [29]. As a result, the calculated values for discriminant validity did not include 1 within the range, indicating that discriminant validity was secured. Convergent validity was verified by computing the Pearson’s correlation coefficient between K-HLAT-8 and Self-As Carer Inventory (SCI) to verify the hypothesis that health literacy and self-care competency are positively correlated [33, 34]. Reliability was verified based on the criterion that Cronbach’s α values of .70 indicate acceptable internal consistency [32]. As for the test-retest reliability for assessing reliability for stability, it was verified based on the following criterion: if the correlation coefficient (r) between two measurement scores and the intra-class correlation coefficient (ICC) are .75 or higher but less than .90, they indicate good test-retest reliability, and if the values are .90 or higher, they indicate excellent test-retest reliability [35].

Data collection and ethical considerations

This study was conducted after receiving approval from the Institutional Review Board of Eulji University (IRB No. EU20-21), and the permission for the use of the assessment tool was received from its developer before using the tool. Data collection was carried out from April 1 to May 30, 2020, and the locations of data collection were the outpatient clinic of a university hospital in D city, a forest bathing site, and a university campus. As to the location of data collection, to secure the diversity of participants, three places that had different characteristics and were easily accessible for the researchers were selected.

The researcher collected data in a face-to-face manner by a self-administered questionnaire survey, and conducted the second data collection 2 to 4 weeks after the first data collection among the 20 people who agreed to participate in the retest among the participants of the first survey.

Before conducting a survey, the participants were given the explanations about the purpose and procedure of the study, voluntary participation, and the right to withdraw from the study at any time if they wanted to, maintenance of anonymity, and guarantee of confidentiality. Data collection was conducted after obtaining written informed consent forms from the participants who voluntarily agreed to participate in the study, and the respondents were given a small gift as a token of appreciation after they completed the questionnaires. The completed questionnaires were immediately put into sealed envelopes and collected by the researcher. Immediately after collecting the questionnaires, the researcher deleted personally identifiable information from the data and coded the data, and the research data was kept in a locked cabinet.

Results

General characteristics of the participants

A total of 210 people participated in this study, and females (60.0%) took up a larger portion of the participants than males (40%). In age, the 19-29 age group (28.6%) took up the largest proportion, followed by the 50-59 age group (27.1%), the 30-39 age group (20.0%), the 40-49 age group (19.5%), and the 60-65 age group (4.8%). As for education level, college or higher (69.0%) accounted for the largest proportion. For monthly income, the group earning 1 million to 2.99 million (37.1%) took up the largest proportion, followed by the group earning 3 million to 4.99million (26.7%). Regarding exercise, 57.6% responded that they ‘exercise irregularly’, 25.7% answered that they ‘exercise regularly’, and 16.7% responded that they ‘do not exercise.’ As to subjective health status, 59.0% assessed their health status as fair, 30 rated their health status as good, and 11.0% reported their health status as poor. As for the presence of chronic diseases, the group without chronic diseases took up 79.5%, and the group with chronic diseases made up 20.5%.

Item analysis

Analysis results showed that the mean scores of the items ranged from 2.75 to 3.60, and the stand deviation of each item ranged from .60 to .89. As for the mean and standard deviation of each subfactor, the mean score for functional health literacy 1 was 7.02±1.46, and the mean score for functional health literacy 2 was 5.90±1.17, The mean score for critical health literacy was 6.40±1.44 points, and the mean score for interactive health literacy was 5.92±1.18. The mean score and standard deviation of the total items were 25.25±4.16 points. The skewness and kurtosis values were less than ±1.97, so they were within the acceptable range for satisfying normality. The corrected item-total correlation coefficient (ITC) values were .46~.71, meeting the threshold criterion of .30 or higher. The ceiling effect and floor effect were less than 30% in all items (Table 1).

Confirmatory factor analysis

The standardized coefficients for the items through confirmatory factor analysis ranged from .54 to .95, meeting the threshold criterion of .50 or higher, so it was confirmed that the items of each factor were valid for measuring the relevant factors (Figure 1). However, the results of the test for multivariate normality did not satisfy normality (Mardia's coefficient of multivariate kurtosis=30.25, C.R.=17.33). Thus, the generalized least squares method was used as the estimation method for confirmatory factor analysis. As a result of examining the model fit of K-HLAT-8, the values of absolute fit indices indicated an acceptable fit as follows: Chi-square(χ²)=23.986 (p=.031), DF=13, Normed χ²(CMIN/DF)=1.85, RMR=.02, and RMSEA=.06. In addition, CFI and IFI, which are incremental fit indices, were both calculated as .94, indicating a good fit (Table 2).

Analysis of item convergent validity and item discriminant validity

The item convergent validity of K-HLAT-8 was verified by three methods as follows. First, the standardized factor loading (β) values of each item were higher than the threshold of .50, ranging from .53 to .95. Also, the average variance extracted (AVE) values ranged from .89 to .97, meeting the threshold criterion of .50 or higher. Additionally, the construct reliability (C.R.) values ranged from .94 to .99, meeting the threshold criterion of .70 or higher (Table 2).

For the item discriminant validity of K-HLAT-8, it was verified by the following two methods. First, in terms of the criterion that ‘if the AVE values are all greater than the squares of the correlation coefficients, the discriminant validity is considered to be secured,’ the range of the squares of the correlation coefficients between latent variables was .31~.71 and the range of the AVE values was .89~.97, indicating that discriminant validity was confirmed. Second, regarding the criterion that ‘the range of values obtained by adding or subtracting the standard error multiplied by 2 from the correlation coefficient value must not include 1’, it was found that the range of the values obtained by the above method did not include 1, meeting the criterion (Table 3).

Verification of convergent validity

To examine the convergent validity of K-HLAT-8, the correlation between the scores of K-HLAT-8 and SCI was analyzed, and it was found that there was a positive correlation between the scores of K-HLAT-8 and SCI (r=.51, p<.001).

Reliability analysis

The results of the assessment of internal consistency reliability showed that the Cronbach’s α value for the total items of K-HLAT-8 was .85. The Cronbach’s α values for each subfactor were .83 for functional health literacy 1 (understanding), .89 for functional health literacy 2 (exploration), .64 for critical health literacy, and .68 for interactive health literacy.

The results of assessing reliability for stability showed that there was a significant correlation between the total scores of the test and the retest (r=.98, p<.001), and the correlations of each factor were as follows: r=.73~.94 (p<.001). The intraclass correlation coefficient (ICC) was .99 (95% CI: .97~.99), and the ICC of each factor was .84~.96, confirming the reliability for stability of the tool (Table 4).

Discussion

Since there are differences in the level of health literacy among individuals, it is necessary for healthcare workers to assess the health literacy of healthcare service recipients and examine their comprehensive health literacy before providing them with a disease treatment process, nursing behavior, or health-related information. In this study, we developed a Korean version of HLAT-8 (K-HLAT-8) to present a comprehensive but simple health literacy assessment tool for Korean adults, and verified its reliability and validity of K-HLAT-8 among Korean adults aged 19 to 65.

During the translation and back-translation processes, the researchers checked for any problems such as the ambiguity of expressions or distortion due to cultural differences in the translated version. During this process, it was thought that respondents may have difficulty in understanding the term ‘information brochures on health issues’, so the term was revised to ‘health information pamphlets.’ Similarly, a Brazilian study [22] found that subjects had difficulty understanding the term ‘information brochures’, so the study revised the term to ‘folhetos/cartilhas’ meaning booklets/textbooks. In addition, although the ‘not applicable’ response option scored as 0 points is included in the original version, in the present study, it was judged to be potentially confusing to respondents and thus was deleted through agreement with the developer of the original tool. However, in the Brazilian study, the response option marked as ‘0 points, not applicable’ was considered semantically similar to the response option marked as 1 point, and was therefore analyzed as the identical response.

In the item analysis, the skewness and kurtosis values and the corrected item-total correlation (ITC) coefficient were all within the acceptable ranges, and there were no items showing the ceiling effect or floor effect higher than the threshold. Thus, the items were considered appropriate for discriminating differences in health literacy.

In the confirmatory factor analysis for testing construct validity, the results for the four factors indicated an adequate level of validity, as in the validation of the original tool and in the Brazilian study [22]. In other words, K-HLAT-8 was found to have suitability as a Korean version of the tool while maintaining the theoretical structure of the original tool.

In addition, through the testing for item convergent validity, it was found that there is a high correlation between the items constituting each subscale of the K-HLAT-8, indicating that each item was appropriately constructed to measure each subconcept. In addition, in the testing for item discriminant validity, testing results all indicated an acceptable level of discriminant validity, indicating that the items of each subscale are differentiated from the items constituting other subscales, and can measure the unique traits of the subscale.

The testing for convergent validity was conducted through verification of the hypothesis that there will be a significant correlation between the scores of K-HLAT-8 and SCI, based on previous studies [35,36] that reported a correlation between health literacy and self-care competency. The analysis results showed a statistically significant correlation, indicating that K-HLAT-8 is a reliable tool for measuring the relationship between mutually converging concepts.

The Cronbach’s α value for the total items of K-HLAT-8 was .85. This is significantly higher than both the Cronbach’s α value of .64 reported by the developer of the original tool and the Cronbach’s α value of .74 reported in a Brazilian study. These results suggest that K-HLAT-8 has a high level of consistency and that each item consistently assesses health literacy. In particular, the Cronbach’s α values for the two areas (understanding, exploration) of functional health literacy were .83 and .89, respectively, indicating a very high level of reliability. This is believed to be a result of improving the clarity and understandability of the items during the translation process. However, the Cronbach’s α values for critical health literacy and interactive health literacy were .64 and .68, respectively, which are not within the acceptable range of .70 or higher. It is thought that these low levels of reliability for critical health literacy and interactive health literacy may be attributed to the fact that there were only two items for each subdomain, and the items did not sufficiently reflect the cultural characteristics of the respondents. In this connection, in Korea, the most frequently used method in searching for health information was found to be web portals, followed by YouTube and the television, and ‘family members or friends’ were ranked relatively low [36]. These characteristics of Korean may have affected the responses to the questions on interactive health literacy, such as “How often can you give help to your family or friends when they ask you questions about health problems?” and “How often can you get information and advice from your family or friends when you have questions about health problems?”

One of the limitations of this study is that it did not evaluate whether specific items were culturally appropriate through cognitive interviews. Cognitive interviews are a method for an in-depth examination of how respondents understand the survey items and whether items are inappropriate or difficult to understand in terms of the cultural background or social context, and this method can increase reliability and cultural validity of the survey items [37]. However, in this study, this evaluation process was omitted, which may have affected the reliability of the tool. Therefore, in future studies, it is recommended that cognitive interviews should be utilized to increase reliability and cultural validity. In addition, the participants were recruited by convenience sampling at a university hospital, a university, and a forest bathing site in a specific region, and consequently, there are limitations in the generalization of research results due to bias in education level with a high proportion of highly educated participants. Moreover, among the participants, the proportion of people aged 60 or older was very low at 4.8%, making it difficult to claim that the tool has been properly validated for older adults. Therefore, in order to expand the scope of application of K-HLAT-8, an additional validation study should be conducted by using samples including participants with various characteristics in terms of variables such as age, education level, and place of residence from diverse communities.

With respect to the utilization of this tool, in terms of its use in the practice of community nursing, this tool can be used in large-scale communities to investigate the level of health literacy in the general population in Korea, and can also be employed to discover vulnerable groups in terms of health information and identify influencing factors for health literacy in order to explore measures to improve health literacy. Furthermore, in terms of health literacy education, K-HLAT-8 can also be used to assess health literacy for the purpose of providing customized health education for individual subjects, and it can also be used to evaluate the effectiveness of interventions, education programs or training programs to improve health literacy. In addition, the development of K-HLAT-8 in this study may also lead to follow-up studies to investigate the relationships between various variables related to health literacy, and K-HLAT-8 may also be employed for an international comparison of health literacy levels.

Conclusions

This study verified the reliability and validity of a health literacy assessment tool (K-HLAT-8) that consists of four factors and eight items. K-HLAT-8 is a comprehensive tool that includes the assessment of the various aspects of health literacy. The reliability of K-HLAT-8 was established through the confirmation of the good internal consistency of the items included in each factor and high test-retest reliability, and the validity of K-HLAT-8 was verified through the verification of construct validity, item convergent validity, item discriminant validity, and convergent validity. The results of this study are hopefully expected to contribute to the utilization of K-HLAT-8 as a simple, easy-to-use health literacy scale in assessing health literacy among adults living in the community.

Figure 1.

Measurement model of the Korean version of 8-item Health Literacy Assessment Tool (K-HLAT-8).

HL=health literacy.

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