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Community health literacy outcome measurement practices: A scoping review of recent interventions

Abstract Introduction Evidence suggests that, while a preference for functional Health Literacy (HL) outcome measurement exists, researchers are converging towards more all‐encompassing instruments. While this claim is present in the HL field, minimal research has comprehensively explored the state of community HL measurement practices at the direct and proxy level. The almost exclusive focus on direct, as opposed to proxy, community HL measurement indicates a review of progress is needed. Objective To identify HL outcome measurement practices for community HL interventions at the direct and proxy level of measurement. Search Strategy Medline, PsycINFO, Web of Science, ERIC, Embase, Scopus, CINAHL, ProQuest Dissertations and Theses, Google Scholar and targeted websites were searched. Inclusion Criteria Studies were sampled from the general population, included HL as an outcome of interest, involved an intervention aiming to improve HL, were English‐text publications and were published ≥2010. Data Extraction and Synthesis Study author(s) and publication years, sample characteristics, intervention profiles and direct and proxy instrument and outcome measurement information were extracted. Full‐text review retrieved 25 eligible studies. Main Results In total, 21 unique direct and 38 unique proxy instruments were extracted. The majority of interventions assessed functional compared to communicative, critical, and other HL domains, with objective instruments more frequently used than subjective or combined objective‐subjective types, though more unique subjective HL instruments were extracted overall. The Test of Functional HL in Adults was the most popular instrument, and perceived health, knowledge, behaviors and health intentions were the most frequent proxy outcome measures, with only the Healthy Lifestyle Behavior Scale‐II and Patient Activation Measure used across multiple interventions. Discussion and Conclusions Direct HL outcome practices endured a unidimensional profile, despite previous suggestions of a convergence towards holistic instruments. This review provides the first overview of proxy HL measurement across community HL interventions, identifying substantial variation in proxy outcome practices. Patient or Public Contribution A University‐based senior librarian contributed to the development of the search strategy, and reviewed iterations of the strategy until refinement was complete. No further public or patient contribution was made given the review‐based nature of the research.


| INTRODUCTION
Health literacy (HL) refers to a person's knowledge, competence, and motivation to understand, access, apply and appraise health information to make effective decisions and judgements concerning health promotion, disease prevention and healthcare to promote or maintain quality of life. 1 Although originally considered a person's health-related reading and writing capabilities, 2 HL is now considered more holistically, with various domains comprising a person's HL.
While many theories and models exist surrounding the domains encompassing HL, including the expanded model 3 and the structural model, 4 the most prevalent remains Nutbeam's (2000) model, which posits that three domains encompass HL: functional, comprising basic reading and writing skills for everyday functioning; communicative/ interactive, concerning more advanced literacy, cognition and social skills to enable active participation, information extraction and derivation of meaning across different communicative modes and circumstances; and critical, considering the appraisal of informationforming the most advanced domain in the model. 5 HL models have undergone a transition towards multidimensionality in recent decades, leading to an increase in HL measurement complexity. With HL now encompassing multiple skill dimensions, further consideration is needed during the measurement phase. However, despite the multifaceted, skillsbased nature of HL as a construct, 6 outcome practices appear to align with unidimensional assumptions of HL, 2 with evidence indicating almost a third of HL instruments being based upon common functional literacy screening tools. 7 While not all HL measurements should incorporate the same outcome practices, this divergence may be cause for concern. For instance, McCaffery et al., who conducted an adult education intervention, 8 assessed HL through five dimensions of the Health Literacy Questionnaire (HLQ), 9 along with thermometer, food and medicine label interpretation taskswith the former assessing communicative and critical HL and the latter measuring Functional HL (FHL). In contrast, Ayaz-Alkaya et al. 10  With estimates indicating 43% of working-age adults in England being unable to comprehend or utilise health-related information, 11 progression in the field is vital. Given the list of negative implications associated with low HL, including lower receipt of mammography screening and influenza vaccinations, 12 all-domain quality of life, 13 non-medication and medication nonadherence 14 and increased mortality risk, 15 enhancing practices in the field is vital for progression. Ensuring interventions appropriately evaluate HL strategies is an important next step, particularly given the suggested convergence towards more holistic, direct HL measurement in recent years. 5 The holistic measurement of HL is an important consideration at the direct level, with all model-based domains important to consider at the commencement of the study design phase. However, a truly holistic depiction of the construct requires consideration beyond model-specific domains alone.
Although direct HL measurements are important, the inclusion of proxy HL measurements may provide further insight into a person's overall HL. To distinguish direct and proxy HL measurement, we define direct HL as any domain(s) from existing HL models or models applied to HL, and proxy HL as any domain(s) not directly attributable to known HL models or which may have the potential to be useful adjunctive outcomes to determine a person's HL. Research has not yet established clear outcome measurement practices at the proxy level, despite community HL interventions measuring a range of variables, including patient activation, 16 health behaviors, 17 health knowledge, 18 and self-perceived health status, 10 among others.
While discussion surrounding direct HL is prevalent, 19 there is minimal discourse around proxy HL measures, and current knowledge surrounding proxy HL measures is minimal.
With community HL interventions being able to elicit behavioral and policy-level change, understanding current HL outcome measurement practices at the direct and proxy domain for community interventions is a necessary consideration, particularly to progress the field of HL overall. This is especially important for community populations, which we define as any nondisclosed disease/condition/ illness or otherwise healthy member of the general population-a definition used in a recent community HL intervention review, 19 whose HL considerations are more generalizable than clinical populations due to the unique characteristics presented by clinical samples. Although a recent review has investigated community HL interventions, 19 the criteria for inclusion was restrictive, did not extend into the grey literature, and focused on the intervention methodology more than the outcome measurements implemented.
The need for a measurement-oriented overview of recent community HL intervention practices is therefore needed.
Consequently, a scoping review was conducted to identify direct and proxy HL outcome measurement practices for recent community HL interventions. The identification of measurement trends at study and instrument-specific levels was the main focus throughout. Given that existing reviews are now dated 12 or had stringent inclusion criteria, 19 the current literature would benefit from further exploration to determine current measurement practices at the direct and proxy level within community HL intervention research.

| Protocol and registration
The scoping review protocol was drafted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses: Scoping Review Checklist and Explanation guidelines, 20  There are less factors to consider for community population HL compared with patient population HL, who may have unique characteristics to consider with regard to HL measurement, particularly given their increased exposure to the healthcare system and impairments which may impact HL assessments. Uncovering current measurement practices in HL interventions for community participants subsequently provides more generalizable findings for measurement consensus across community samples than patient/ noncommunity samples.
The decision to conduct a scoping review was based on reach, enabling a broader scope of inquiry and promoting a wider overview of the literature. 21 As scoping reviews typically do not include quality/appraisal assessments, 22 24 In reference to consulting with contact experts, consultations with two HL experts yielded the above series of websites as appropriate resources (See Table 3 for the search strategy).

| Review process and data charting
One reviewer worked independently to screen eligible abstracts for full-text review. After the initial screening, two reviewers worked independently to screen full-text items for inclusion. Once reviewed, both members discussed the decisions made and verified the screening accuracy. A third reviewer was available to make final decisions on any items in the event that discrepancies arose between the first and second reviewers. The researchers resolved disagreements that could not be resolved by consultation with the third reviewer through discussion with the remaining members of the team.

| Screening and extraction
The scoping review yielded 270 items after the initial screening, with full-text review identifying 25 items for synthesis (see Figure 1).

| Data charting table
A plethora of study characteristics and outcome practices were retrieved, including author and publication details, listed under the study column; sample characteristics, sizes, and nationality, identified within the sample and sample size column; intervention delivery, type, and material covered, extracted in the intervention column; direct and proxy instrument names, provided under the namesake columns, and the instrument domains assessed at the direct and proxy level, listed under the direct and proxy outcomes column (see Table 4).  Figure 2).

| Direct health literacy outcome and instrument frequencies
The Test of Functional HL in Adults (TOFHLA) was the most frequently extracted direct HL instrument, with short-form (n = 3 10,28,29 ) and normal variants (n = 5 31

| Categorized direct health literacy outcome and instrument frequencies
Frequencies were charted across six formats Figure 3. None.

Individual domains extracted
Direct: other HL. Proxy: N/A.

Note:
Under the sub-heading Delivery, within the wider Intervention column, we reported the location of the intervention being conducted where possible. We reported this information when available to provide further context, with the inconsistent presentation being due to studies failing to report study location information. The Adult Health Literacy Scale was described in minimal detail within Ayaz-Alkaya et al., 10 and the original instrument development paper was used to support the categorization of the measure as a direct or proxy measurement. However, the original paper by Sezer and Kadioğlu (2014) was non-English, and subsequently uninterpretable. The instrument was subsequently identified as an unknown direct health literacy measurement. c We were unable to gain access to the Fernández-Gutiérrez 34 full-text paper, and were unable to categorize the outcomes assessed for the HLS-APP-Q14, which appears to be a study-specific intervention knowledge measurement. Given our lack of confidence in the categorization, we categorized the HLS-APP-Q14 as an unknown direct HL measurement.

| Proxy instrument frequency analysis
In summary, 38 unique proxy HL instruments were extracted, with thematic analysis retrieving the following measurement themes: anthropometric, developmental, and physiological characteristics; perceived health, knowledge, behaviors, and health intentions; perceptions of healthcare, usage and patient experiences; intervention experience-based evaluations; psychosocial, general and nonhealth factors; and miscellaneous (n = 1).
One proxy HL outcome tested the capacity to teach HL for education center directors, but this was not tested in the primary sample within which HL improvement was sought. 28 The measure was not an assessment of active participants in the intervention, and was listed separately-forming the miscellaneous group-and did not feature in further data representations in Figure 4.

The Healthy Lifestyle Behavior Scale-II (HLSBS-II)/Health-Promoting
Lifestyle Profile-II (HPLP-II) was the most common proxy HL instrument utilized across community HL interventions (n = 3 17,10,37 ). The second most frequently implemented instrument was the PAM (n = 2 16,44 ), and the remaining 36 instruments were utilized once.

| Proxy outcome categorization
Proxy measures were categorized into one of five measurement categories (see Figure 5).

| Combined direct and proxy measures
Two instruments measured direct and proxy HL simultaneously. The study-specific theory of planned behavior questionnaire (n = 1 16 ) con- The majority of proxy instruments were utilized individually across the studies, excluding the PAM and HLSBS-II/HPLP-II, which were utilized three and two times, respectively.
Across both direct and proxy HL measures, a significant degree of measurement variance was reported, demonstrating variation and potential disagreement towards outcome measurement at the domain, instrument, direct, and proxy level within present-day community HL intervention research.

| Functional domain frequency
The prioritization of FHL is expected, reflecting existing evidence in the field. Around one in every three HL instruments were previously suggested to be based on popular functional measures, 7 with a functional preference noted across adult 50  with aims relating to the improvement of HL in general-implying an intended improvement across multiple HL levels-but only incorporated direct outcomes targeting FHL. 17,28,42 These practices indicate that, while the majority of studies successfully apply FHL outcomes in reference to their intervention aims, research may struggle to identify appropriate direct HL evaluations beyond the functional level, ignoring the assessment of potentially relevant HL skills.
Given the frequent use of the HL term in titles and key word sections of many interventions, these unidimensional practices infer that HL may be seen as a label for established interventions and outcomes 19 rather than as the multidimensional, skills-based construct that it is, 6 with communicative and critical components frequently overlooked. This may explain why investigations referring to HL as a general concept only assessed FHL, as they indirectly attribute HL as more of a descriptor rather than a construct. An individual's skill in one HL domain does not represent their overall HL, yet this approach infers the opposite is true, which may lead to inaccurate representations of public HL.
One problem with the label perspective is that it does not explain the preference for FHL outcomes observed, as only a subset of studies did not successfully match FHL outcomes with their intervention goals. This preference may be a consequence of the hierarchical nature of Nutbeam's model. 5 To build upon an individual's communicative or critical HL, they must first possess adequate FHL, and because of this interventions may attempt to focus exclusively on FHL to understand, identify and improve a person's foundational HL before they can explore higher levels of the construct. In this regard, FHL acts as an important catalyst to enable access to higher order HL skills in the public, and is a fundamental level for people to self-manage their health. The scope for public HL change may be most opportune at the functional level, and may contribute to the long-standing FHL prioritization at both the domain and instrument level.
Although a functional prioritization for direct HL outcomes is appropriate when the intervention aims are concerned with FHL, this review identifies a problem with HL outcome practices when considered with respect to community HL intervention aims. More specifically, some studies incorporated measurements that do not necessarily evaluate the proposed intervention HL-oriented goals, 17,28,42 indicating a misrepresentation with the construct as opposed to a preference for evaluating FHL. Although the majority of studies appropriately applied direct HL measurements relative to their intervention aims, a minority did not, and there may consequently be scope for an expert-led measurement framework to clarify HL assessment at the direct level to simplify the HL-related evaluation process.
Such a framework could also consider the instruments used to measure the outcomes. Currently, the functionally-focused TOFHLA

| Communicative and critical health literacy omission
While communicative and critical HL were measured more consistently than previous evidence indicates, 19

| Instrument type and functional trend
The focus towards functional instruments like the TOFHLA may be a consequence of community HL intervention research prioritising instrument type in addition to the domain assessed. While less unique objective instruments were identified (n = 6) compared to subjective instruments (n = 9), the frequency by which interventions used objective instruments was greater than that of subjective instruments, with 13 interventions using objective HL instruments 16,17,10,[28][29][30][31][32][33][34][35][36]42,43 versus the 10 interventions incorporating subjective instruments. [37][38][39][40][41][43][44][45]47,48 Though the difference between these frequencies was minimal, a preference emerged for objective instruments.  Although this review provides a fruitful, informative overview of HL measurement practices for community HL interventions on a broad scale, some limitations emerged. First, the findings do not evaluate the quality of HL interventions, primarily due to scoping reviews typically not including quality or appraisal elements. 22 Ensuring that interventions are being evaluated appropriately is arguably a greater consideration in the short-term, and understanding existing community HL intervention outcome practices will foster an efficient and knowledgeable appraisal moving forward. Additionally, only English-text studies were included, leading to potentially relevant intervention omissions.

| CONCLUSION
This scoping review provides important evidence regarding the trends in HL outcome measurement across current community HL interventions.
Despite previous suggestions of a potential convergence towards a more holistic HL measurement practice, 7

ACKNOWLEDGMENTS
We would like to express our gratitude to the colleagues who supported us throughout the review process, providing in-depth feedback to further improve the research process. We would particularly like to thank our senior librarian at the University of Nottingham, who helped provide the framework for a comprehensive and improved search strategy aligned with the objectives of this review. This investigation was partially funded by the principal investigator's PhD Studentship (L.S.), provided by the University of Nottingham.

DATA AVAILABILITY STATEMENT
The data which support the findings of this study are openly available at the Open Science Framework (DOI 10.17605/OSF.IO/4WRMQ), with the main body of evidence provided within the article.

TRANSPARENCY STATEMENT
I confirm that this manuscript is an honest, accurate and transparent account of the findings reported from this review; that no important parts of the study have been omitted; and that any discrepancies from the review have been highlighted and discussed.