How Do You Obtain Informed Consent When Participants Have Limited Literacy?

What if a participant can understand your study but struggles with written information?

A consent form can satisfy every institutional requirement and still fail the person reading it. Long sentences, unfamiliar research terminology, dense pages, percentages, and technical descriptions of risk may make important information difficult to understand, particularly for participants with limited literacy or numeracy.

The problem is not solved simply by handing someone an easier-looking form. Informed consent is a communication process, not a reading test. CIOMS describes consent as a two-way process in which researchers provide relevant information and ascertain that the prospective participant adequately understands the material facts before deciding whether to participate.

That distinction matters. Limited literacy should not automatically be treated as limited capacity to make a consent decision. A person may have difficulty reading a research document yet be entirely capable of understanding the study when the information is communicated appropriately.

Adapt the consent process to the participant, not the participant to the form

Design consent around understanding rather than reading ability

Limited literacy does not automatically make consent invalid

The ethical question is not whether someone reads quickly, writes fluently, or has reached a particular educational level. The central questions are whether the person receives the information needed to make the decision, adequately understands that information, has an opportunity to ask questions, and decides voluntarily.

CIOMS explicitly recognizes that comprehension depends partly on educational level, but also on how researchers communicate, the circumstances in which consent occurs, and whether information is presented patiently and sensitively. In other words, comprehension is not simply a characteristic of the participant. The design of the consent process can either support or obstruct it.

This distinction also prevents an ethically troublesome shortcut: asking someone else to decide merely because the prospective participant does not read well. Whether another person may consent on a participant's behalf depends on the participant's authority and capacity to consent and on applicable law and ethics requirements, not simply on literacy.

Start by making the information itself easier to understand

Consent information should use ordinary language appropriate to the intended participant population. OHRP recommends replacing technical terminology with familiar words, keeping sentences relatively short and conversational, breaking dense material into manageable sections, and explaining unfamiliar concepts. Its current consent-form checklist also cautions researchers not to assume that a favorable readability score necessarily means the material is clear.

That last point is easy to miss. A readability formula can flag difficult text, but it cannot tell you whether a participant understands randomization, confidentiality, placebo, withdrawal, research-related risk, or the difference between research and ordinary care. Simplifying vocabulary is therefore useful, but simplification should preserve the information necessary for an informed decision.

Do not rely on the written form as the entire consent process

For participants with limited literacy, oral communication becomes especially important. FDA guidance on low literacy and numeracy specifically emphasizes oral presentation of consent information when necessary to make the process understandable. OHRP likewise describes informed consent as an ongoing exchange rather than merely a signed document.

A researcher might therefore explain the study conversationally, pause after important concepts, invite questions, and use approved diagrams, pictures, videos, narration, or other aids where these genuinely improve understanding. CIOMS specifically recognizes oral presentation, pictographs, summary tables, and appropriate audiovisual aids as useful supplements to written information.

These supports should clarify the same study that the ethics committee or institutional review board approved. Researchers should not improvise materially different descriptions of risks, benefits, procedures, or participant rights simply because the conversation is oral.

Check understanding instead of asking, "Do you understand?"

A yes-or-no question provides weak evidence of comprehension. Participants may answer yes because they are embarrassed to admit difficulty, want to please the researcher, assume they are expected to agree, or simply do not realize that they have misunderstood something.

A better approach is to ask the participant to explain important information in their own words. This is often described as a teach-back approach. The purpose is not to examine the participant. It is to discover whether the research team has explained the study effectively enough.

Useful prompts might include:

• "Can you tell me in your own words what you would be asked to do in this study?"
• "What could happen if you decide not to join?"
• "What are the main risks or inconveniences you remember?"
• "If you join today and change your mind later, what can you do?"
• "What would you like me to explain again?"

If an answer reveals a misunderstanding, explain the point again in another way and check comprehension once more. WHO consent materials similarly recommend targeted questions rather than treating a participant's statement that they understand as sufficient evidence of understanding.

Literacy and numeracy are related but not identical problems

A participant who can comfortably read ordinary prose may still struggle with probabilities, percentages, frequencies, or comparisons used to describe risk. FDA guidance therefore discusses low literacy and low numeracy together when considering whether modifications to the consent process are needed.

When numbers matter to the decision, explain them in a consistent and concrete form. For example, an approved explanation might present a probability as a frequency such as "about 1 out of 100 people" rather than expecting the participant to interpret a percentage without context. Visual aids may help, but they should represent the underlying information accurately rather than make a risk appear larger or smaller than it is.

Limited literacy is different from being unable to read the form

These situations overlap, but they should not be treated as identical. Someone with limited literacy may be able to read parts of a simplified consent document while benefiting from oral explanation. Someone who cannot read the document requires a process that does not depend on reading it independently.

For clinical trials conducted under ICH E6(R3), when a participant or legally acceptable representative is unable to read, an impartial witness should be present throughout the informed consent discussion. The witness attests that the information was accurately explained and apparently understood and that consent was freely given. Other regulatory systems have their own requirements. The specific procedures for a participant who cannot read the consent form therefore need to be determined under the framework governing the study.

Do not confuse a literacy problem with a language problem

Simplifying an English consent form does not solve the problem if the prospective participant primarily understands another language. Literacy concerns how readily a person can use written information; language concerns whether the information is being communicated in a language the person understands.

If language is also a barrier, the research team needs to address informed consent across different languages. Translation and interpretation requirements may apply in addition to literacy adaptations.

Think about literacy before recruitment begins

If the target population is reasonably expected to include people with limited literacy, accessibility should be built into the protocol and consent materials rather than improvised after recruitment starts. OHRP suggests considering characteristics of the prospective participant population when developing understandable consent information, while CIOMS expects researchers to allocate adequate time and resources to the consent process.

Researchers can also ask people unfamiliar with the study, or members of the intended participant population where appropriate, to review draft materials and explain what they think the information means. That kind of testing can reveal ambiguities that a research team has stopped noticing after reading its own protocol for the forty-seventh time.

What an adapted consent conversation might look like

The important feature of this example is not the particular visual aid or wording. It is the sequence: communicate, discuss, assess understanding, clarify, allow a decision, and then document it. A signature records the decision; it should not substitute for the process that makes the decision informed.

Common mistakes when literacy is limited

Build accessibility into the consent process before you meet participants

If limited literacy is reasonably foreseeable in your study population, plan for it when developing the protocol, recruitment procedures, consent materials, staff training, and ethics submission. Do not leave individual fieldworkers to invent their own solution at the moment of enrollment.

Your research ethics committee or institutional review board should review the planned consent process. Requirements differ across jurisdictions and types of research, particularly concerning witnesses, short-form consent procedures, oral consent, signatures or marks, and waivers of documentation. A method permitted in one regulatory setting should not automatically be assumed acceptable in another.

The broader principle is more stable: informed consent should give people a genuine opportunity to understand what participation means and decide for themselves. The form is one instrument for accomplishing and documenting that task. It is not the task itself.

Before recruiting participants with limited literacy

Questions about limited literacy and informed consent

Consent should measure a decision, not reading ability

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