In this review, health literacy includes literacy (narrative), numeracy (numerical/mathematical), and digital (electronic/digital media) factors.

Health literacy definitions have changed over time, with their focus ranging from cognitive (comprehension, critical thinking skills) to behavioral (e.g., search and application of information, agency) to affective (e.g., self-awareness, self-efficacy) factors (20). Due to the variability of definitions and factors, Sørensen (21) proposed an integrated health literacy model encompassing public health and medical views of health literacy (i.e., competence/skills/abilities, action, information, objective, context, and time). More recently, Healthy People 2030 (HP2030), the decade-long initiative to improve the nation’s health through health promotion and disease prevention initiatives, updated the definition of personal health literacy to “the degree to which individuals have the ability to find, understand, and use information and services to inform health-related decisions and actions for themselves and others” (22). HP2030 also updated the role of health literacy and presented it as one of its overarching goals (23). Such updates were necessary to assess health literacy as a social determinant of health and bring closer and more careful attention to the critical role that health literacy skills have over health, health care, and health outcomes (24-26).

Narrative, as a concept of communicating in a written format, goes beyond such capacity and includes competencies that enable readers to acknowledge and understand structured textual elements and are fundamental to processing concepts and building meaning (27). Today, the written word is available to patients in paper, digital, and audio formats. Delivering information through digital media is more common, and its use is growing. Understanding this form of information delivery requires narrative and digital literacy skills. Such a combination may present additional challenges due to the parallel need for such skills. This may be evident in the disparities in activation of (e.g., accepting an electronic invitation) and access to patient portals by disproportionately affected populations, such as African American and Spanish-speaking Hispanic/Latino patients when reviewing their diagnostic tests (e.g., blood, urine, imaging) after emergency department visits (28). These disparities and the need to use multiple literacy factors mainly inhibit the accessibility and navigation of patient portals for patients with limited English proficiency due to a lack of multilingual options, internet access issues, and the complexity of a multistep process to activate an account by using an activation code found in discharge or visit summary papers or requesting an activation code (28).

Another factor impacting the successful understanding of health-related messages is the comprehension level at which the information is written. The general recommendation is to write health information at a sixth-grade level to match the general population’s reading level (29). However, Daraz et al. found in a systemic review (157 studies) that analyzed a total of 7891 US and Canadian websites (comprised of academic, government, non-profit, media, private/commercial, and other site types that included health information addressing/targeting the general public) that the mean readability grade level of the text (health information) presented in all websites ranged between grade 10 to 15, surpassing the recommended sixth-grade comprehension level (30). Presenting health information at a higher than the recommended readability grade level may make the information less appropriate for general public use and potentially impact the understanding of health information.

In 2022, Flores et al. argued that the value of health communication is negatively impacted if the needs of the intended audience (access to and understanding of messages) are not met while affecting the actionable nature of health communication (31). Thus, the narrative is a pillar of health communication. Patient-centered health communication would significantly benefit from systematically and consistently implementing the sixth-grade comprehension level in health communication publications allowing patients, regardless of their literacy level, to understand information the first time they read it. Communicating health information with simple messages benefits both low-and high-literacy individuals (32). Although the Plain Writing Act of 2010 indicates the use of plain writing in US federal documents providing information about government benefits or services, a new legislative initiative (Clear and Concise Content Act of 2023) would update the Plain Writing Act of 2010 and expand documents covered to nearly all information (except regulations) that public agencies post to the public (33, 34). Such an update may provide tangible options to address health literacy issues systematically.

A narrative factor to consider is the language in which information is communicated. The U.S. Census Bureau estimates that more than 350 spoken languages are represented in the US population (35), with more than 25.5 million people (8.2% of the US population) speaking English less than “very well” (36). Populations with such linguistic characteristics are categorized as having limited English proficiency (LEP). Anti-discrimination and enabling resources, guidelines, and regulations for these populations include Title VI of the Civil Rights Act (37), Executive Order 13166 (38), Executive Order on Advancing Racial Equity and Support for Underserved Communities Through the Federal Government (8), Culturally and Linguistically Appropriate Service (CLAS) standards (39), LEP.gov (12), and the Clinical Laboratory Improvement Advisory Committee (CLIAC) Recommendation 5 from October 2020 (40), among others. Despite those protections and resources, Hispanic/Latino and populations with LEP tend to have less access to patient web portals and laboratory testing portals, lower health literacy, and are more prone to medical errors (28, 41, 42).

Although the direct release of test results to patients increases patient engagement for English speakers, it may also cause anxiety and confusion, especially when there is no provider interpretation of the results or contextualized medical advice (43-45). These circumstances make understanding laboratory test results especially challenging for native English speakers with limited health literacy skills (46). Adding a lack of English proficiency to the existing narrative with readability higher than the recommended sixth-grade level may decrease access and understanding of health communication messages, including test results. The COVID-19 pandemic proved this effect on speakers of Spanish and Chinese (including traditional, simplified, and other languages from China), the 2 most commonly spoken languages in the US after English. Speakers of Spanish and Chinese languages were subject to disparities in 3 aspects: lack of receiving information consistently on protective health behaviors by public health and government agencies; instead, receiving that information from traditional (e.g., tv) and digital (e.g., social media), family and friends; and, facing challenges with information that was perceived as discriminatory toward Latinx and Chinese people (47).

Although narrative bears great importance, health communications, particularly laboratory test results, are presented or reported using numbers and reference intervals. The addition of digital components as part of the widespread availability of electronic health records and patient portal resources extends the need for digital literacy and potentially contributes to additional challenges. Addressing health literacy issues should account for the challenges arising from the interactions of all these factors.

Numeracy is the ability to read and understand numerical information. In the context of health literacy, it includes the ability to understand clinical and public health data (48). The 2 types of numeracy are subjective or self-identified “confidence in understanding mathematical data, and objective or measurement of a person’s actual math skills” (48). A patient’s specific numeracy type may affect their disease risk perception and health decisions. In the context of health literacy, numeracy plays a critical role in understanding public health, laboratory, clinical, and therapeutic assessments, recommendations, reports, and instructions. For example, numeracy can impact people’s understanding of data, decrease bias, and improve statistical information processing (49, 50). The COVID-19 pandemic offered the opportunity to prove the relevance of numeracy in health behavior and public health. For example, using epidemiological data about mask mandates, Hutmacher et al. studied how numeracy may interact with motivated reasoning to draw conclusions not necessarily based on rationale and objectivity (49). Similarly, Lau et al. conducted surveys in the US, United Kingdom, and Canada during the pandemic to understand basic numeracy, health numeracy in context, and health-related attitudes and behaviors. The authors found that basic numeracy was positively associated with health numeracy, but neither of those 2 factors were related to COVID-19 health-related attitudes and behavior in the 3 surveyed locations (50). The need for an unbiased understanding of public health information is paramount. This need became more evident during the COVID-19 pandemic in its association with greater susceptibility to misinformation in multiple countries, including the US (51).

Moreover, recent evidence in the context of the COVID-19 pandemic emphasizes the importance of numeracy for the population to understand the issues originating from a global pandemic (52). However, evidence also indicates that numeracy alone is insufficient to influence people’s attitudes toward health, disease severity, and their willingness to follow public health advice (50). Similar associations between numeracy and factors impacting health outcomes were identified in different types of cancer studies, such as breast (e.g., less understanding of disease stage and difficulties in completing decision aid tools), colorectal (e.g., attitude toward screening), and prostate cancers (e.g., risk assessment and treatment choice), as well as heart failure and other conditions (53-55). The role of numeracy becomes more essential due to the immediate availability, number, and frequency of epidemiologic reports and data sharing through digital media. Thus, numeracy and health literacy are critically in need of a cohesive articulation with digital literacy.

Our ever-advancing technology requires specific technology-based factors and skills, such as broadband access, updated hardware, and foundational digital literacy skills. Formerly known as computer literacy, digital literacy involves skills to adapt to accessing and managing hardware (desktops, laptops, and mobile devices) and user interfaces (UIs) that require other forms of hardware (e.g., mouse, touchscreen, stylus, and voice activation) and software (e.g., voice activation, talk to text). Managing the hardware/UI combination may appear more intuitive to digital natives, those individuals who were born or grew up with such electronic and digital stimuli (56).

The digital divide limits affected individuals’ ability to access, manage, and understand essential data points to make informed health decisions. This is particularly important for older patients with limited digital skills who have difficulty navigating mobile phone UIs (57). This confluence of factors may negatively impact the meaningful participation, access, and use of digital information and resources necessary to make informed health decisions (58).

Furthermore, the development and penetration of direct-to-consumer testing, wearable devices, and the Internet of Things (IoT) will likely change digital literacy skills from relevant to required (59, 60). Voice-activated IoT technologies may present challenges and opportunities in extending or addressing the disparities in overall language proficiency and health literacy, impacting the diagnosis and management of chronic diseases, such as diabetes and cardiovascular disease, that require laboratory testing where narrative and numeracy impact the interpretation of results and decision-making process to implement actions to improve health outcomes (45, 61, 62).

In 2003, results of the first nationwide US assessment of adult literacy skills showed a concerning baseline for health literacy in adults: below basic level (14%), basic level (22%), intermediate level (53%), and proficient level (12%). The assessment levels increased the difficulty of 3 tasks primarily: locating, identifying, and analyzing information in text and documents, going from the most simple and concrete literacy skills in below basic to more complex and challenging literacy activities in proficient; and identifying and using quantitative information to perform mathematical calculations to solve problems, from identifying and performing simple mathematics in one-step problems in below basic to using more abstract quantitative information to solve problems that require multiple steps (63). A more recent report using surveys from 2012 to 2014 from the Program for the International Assessment of Adult Competencies (PIAAC) showed overall improvement (64). However, updated PIACC data (2012 to 2017) showed low literacy and numeracy patterns in US southern and southwestern states (46).

Although internet connectivity varies within the US and other countries, the influence of digital environments and the ubiquity of connectivity and access to information require that improvement efforts account for health literacy and the salient effects of its components (digital literacy and numeracy). The United Nations Sustainable Development Goals attempted to address the global deficiencies in literacy, particularly numeracy, via Target 4.6, which aims for youth and adults to achieve literacy and numeracy by 2030 (65). Although the effects of the COVID-19 pandemic are yet to be fully assessed, a report from the United Nations pointed out the disruptive effects of the pandemic as a global education crisis (66), likely impacting health literacy as well. The differences in literacy levels are critical to understanding the numerous epidemiologic data and reports developed during the pandemic. In 2021, Abel and McQueen proposed the development of Critical Health Literacy in a Pandemic, contextualizing and accounting for sociocultural factors to support patients and communities and their active and informed participation (67).

Moreover, critical literacy skills are required for patients to successfully access and interact with information containing clinical laboratory testing instructions and results. Disparities in access have been reported for laboratory testing and radiology results in the emergency department in adults and children (28, 68). Housten (69) found a significant association between language acculturation (more use of English, less use of Spanish) and health literacy. Similarly, language acculturation also influences the perception of discrimination and quality of care by Spanish speakers and their overall patient experience (70). Language acculturation is a process that takes years, sometimes decades. During this transitional period, Spanish speakers with LEP, and speakers of other non-English languages, are at a disadvantage when interacting with health information. Regarding laboratory test results, individuals with LEP face multiple factors that hamper their understanding (e.g., language access, digital literacy, narrative, numeracy). Diminished access or lack of effective access and understanding of health information puts individuals with LEP at higher risk of negative events in healthcare and other life aspects, such as financial, civic, and in the workplace (71, 72). Thus, addressing these issues provides a way to decrease multiple disparities that individuals with LEP face and enhance their equity.

Once access and digital literacy barriers are overcome, patients face the complexities of medical terminology, reporting using different systems of units (the international and imperial systems of units), and limited understanding of laboratory testing results and the reported ranges (e.g., numbers, formats) in which they are presented (45, 73).

Although evidence indicates that patient engagement increases and is preferred by patients, the need for help in understanding and interpreting results is essential (43, 45). Narrative and numeracy play essential roles in understanding results. However, the visual display of results also plays an important role that may account for various learning styles and preferences (74).

Clinical testing results usually include reference intervals (RIs) to determine a comparison point and assist in the determination (quantification) of normal values, higher risk (pre-diagnosis), and diagnosis. RIs are generally determined using one of 2 ways. Through a direct method by gathering samples from healthy individuals representing the population to establish lower and upper-end references, and an indirect method by using research literature, information from equipment manufacturers, and data from other sources (75). Although the direct method may be ideal for establishing relevant RIs, it involves high costs, extended time, and logistics, making it a challenging route for most laboratory facilities to establish RIs (76). Transferring RIs from other sources (e.g., mining data from electronic health records and other large data sets) may also introduce heterogeneity (i.e., population representation different from the population where the RI will be applied), making it challenging to apply it to pediatric patient populations (77). Patients’ assessment of risk and the need to take action when reading laboratory test results requires a design that combines RIs with simple graphic designs that facilitate the interpretation of results (78). Such design would have to be studied in instances that include pre-test selection (e.g., direct-to-consumer testing kits), clinical sensitivity, and specificity (false positives and false negatives).

Although mining data may seem like a promising solution, unless there is a realistic representation of the population diversity in the research study population, the RIs may not effectively reflect the population’s needs and characteristics. Diversity in research remains an elusive reality with persistent barriers that require system-level changes in research recruitment, diversity of researchers, and buy-in from populations with multiple historical disappointments with research participation, both in voluntary and involuntary ways (79). An indirect method may continue existing disparities or create new ones by applying a “one size fits all” approach that does not account for biological and physiologic characteristics or mechanisms of underrepresented populations and overcoming recruitment barriers in biomedical research (80). A recent example is the removal of race from the estimated glomerular filtration rate (eGFR), given that race is a social construct, not a biological one. Using race to modify the eGFR in African American individuals rendered values that were 16% higher, potentially impacting diagnostic and therapeutic decisions, such as more aggressive treatment and less likelihood of getting a kidney transplant, among others (81). The American Association for Clinical Chemistry recently published a guidance document calling all laboratories for the immediate implementation of the creatinine-based eGFR equation in adults with chronic kidney disease (CKD). This equation, called CKD-EPI-2021, was developed without a race coefficient to provide a more accurate test, initial or confirmatory as appropriate in the clinical setting. The new CKD-EPI-2021 equation represents progress to achieve a more equitable management of kidney disease (82, 83). Accurate and timely methods to update RIs should account for the current and future changes in population demographics impacted by social determinants of health, immigration patterns, and global health needs.

Patients need to interact with laboratory test results with a minimum level of understanding of RIs to make informed health decisions and engage in health behaviors that are conducive to achieving all levels of prevention. Positive is not always good, and negative is not always bad.

Equitable access to patient portals is only the first step. Presenting laboratory test results to the general public requires standardization and systematic inclusion of 3 critical aspects: (a) health literacy, (b) foundational use of culturally and linguistically appropriate resources, and (c) tools to contextualize results to help patients understand laboratory test results and make decisions that lead to actions that prevent the onset of disease(s) or encourage patients to seek appropriate treatment(s).

Using culturally and linguistically appropriate resources provides a pathway to support the language acculturation process of individuals with LEP. For example, Spanish-speaking patients prefer in-person disclosure of results using their preferred language to understand and address concerns when receiving high-risk results involving complex concepts such as polygenic risk scores (96). Aside from the complexity of health-related concepts, preferences should be understood as ways to ensure understanding and learning concepts relevant to health and disease management processes. It is not feasible in healthcare, historical, social, cultural, and economic terms to ignore such needs if the goal is to offer a patient-centered system of care (97).

Current and future clinical and public health needs may lead to the rapid growth of direct-to-consumer (DTC) testing and wearable devices. Such growth may present opportunities to extend health communication outreach to disproportionately affected populations that may benefit from more affordable DTC testing. The challenges include avoiding the continuation of existing disparities that hamper understanding and an informed decision-making process based on health communication that does not fully account for low health literacy (60, 98).

Responding to multiple and diverse needs requires using design systems that innovate with enough flexibility to account for complex and changing needs, populations, and systems (e.g., testing, healthcare). The pillars of designing new approaches to healthcare benefit from human-centered designs and systems that focus on people’s needs and concrete experiences (e.g., language proficiency, cultural, and social assimilation) (99, 100).

A call to action is warranted to laboratory professionals and clinicians to support the review and redesign of patient portals with a patient-centered perspective, through multidisciplinary work to ensure systematic implementation of clear communication through plain writing to achieve health equity through improved health literacy efforts. Similarly, federal and state organizations may also contribute by providing guidelines, resources, and legislative initiatives, such as the Digital Equity Act of 2021 and the Clear and Concise Content Act of 2023.