A questionnaire designed to measure how well pet owners understand cancer information has shown that veterinary communication may need to be tailored to the people receiving it. In a study of 1,548 owners of dogs and cats, researchers tested not only whether participants knew the correct answers, but also whether individual questions could distinguish between people with higher and lower cancer health literacy. The results suggest that a tool developed specifically for veterinary oncology can identify owners who may need additional support, even though the questionnaire was generally easy for this highly educated group. The findings offer a technical foundation for improving conversations when a companion animal receives a cancer diagnosis, a moment when unfamiliar terminology, treatment choices and emotional stress can make information difficult to absorb.
Health literacy refers to the ability to obtain, process and understand health information and use it when making decisions. Cancer health literacy is a more specific form concerned with concepts encountered in cancer prevention, diagnosis and treatment. In veterinary medicine, the construct applies not to the animal patient directly but to the owner who must interpret professional advice, weigh options and often make decisions on the animal’s behalf. Those decisions can involve surgery, chemotherapy, radiation, palliative care, prognosis and treatment risks. The research team had previously developed a 30-question cancer health literacy questionnaire for veterinary clients. In this second analysis, the investigators examined the statistical behavior of each question and explored whether questions worked differently for groups defined by education and previous experience with cancer.
The survey was distributed remotely through the Qualtrics platform to clients attending the Pet Health Service, the general-practice branch of the Kansas State University Veterinary Health Center. Invitations were sent between January 2015 and December 2020. Of 13,446 emails distributed, 1,773 responses were received, producing a response rate of 13 percent. Researchers included 1,548 respondents who answered at least 75 percent of the 30 cancer health literacy questions and supplied some demographic information. The questionnaire also included 14 demographic questions, although completing every demographic item was not required. Participants’ scores ranged from six to 30 correct answers, with a mean of 26.7 and a median of 27, indicating that most respondents performed near the top of the available range.
That concentration of high scores created a ceiling effect, meaning many participants answered the easiest questions correctly and left relatively little variation for the test to measure. The item-difficulty index used by the researchers was the proportion of respondents answering a question correctly; unlike ordinary language, a high value meant an easy item. Across the questionnaire, the median difficulty index was 0.94, with values ranging from 0.50 for a question about feline leukemia virus risk to 0.99 for several questions, including items concerning the next pill, biopsy, appointment location, cancer stages, inoperable tumors and radiation treatment. The average difficulty index was 0.89. These figures show that the instrument was not demanding for this sample, but ease alone does not determine whether a question is useful.
The researchers therefore also calculated item discrimination, which measures how effectively a question separates respondents who perform strongly overall from those who perform weakly. The index compares correct responses from the highest-scoring 25 percent with those from the lowest-scoring 25 percent. Values can range from minus one to one, with larger positive values indicating stronger discrimination. The median was only 0.05, and the mean was 0.08. Ten questions had negative discrimination, meaning lower-performing respondents were more likely to answer them correctly than higher-performing respondents. Such a result can arise from ambiguous wording, misunderstanding, measurement error or a question that draws on a different skill from the one the test is intended to assess. Only six items exceeded 0.2: questions concerning feline leukemia virus risk, high-calorie diets, book chapters, airborne tumor spread, dose timing and palliative care. These questions appeared to provide the clearest information about differences in ability.
To examine the structure of the questionnaire, the team used item response theory, a family of statistical methods that models the probability of a correct answer as a function of an unobserved trait—in this case, cancer health literacy. Unlike a simple total score, item response theory can estimate how difficult a question is and how sharply it discriminates across the underlying ability scale. Analyses using parallel analysis and the Hull method supported a single underlying factor, or unidimensional structure. Although a three-parameter logistic model could in principle account for guessing on multiple-choice questions, its guessing estimates had large standard errors and the model encountered convergence problems. A likelihood-ratio comparison found no meaningful advantage for the more complex model, while information criteria and overall fit favored a two-parameter logistic model. The researchers used that model for subsequent analyses, finding that it fit the data well and was especially informative at lower ability levels.
The study also tested differential item functioning, or DIF. DIF occurs when people with comparable levels of the underlying ability have different probabilities of answering a particular question correctly because they belong to different groups. Detecting DIF can reveal wording or content that introduces bias unrelated to the construct being measured. Among education groups, seven questions displayed DIF: oral cancer, risk of complications, palliative care, airborne tumor spread, survival rate, feline leukemia virus risk and book chapters. The pattern suggested that some questions relied partly on numeracy, vocabulary, reading comprehension or basic biology in addition to cancer-specific knowledge. However, the combined differences did not produce significant differential test functioning, meaning the questionnaire as a whole did not show a statistically significant education-related scoring bias. Participants with at least a bachelor’s degree scored 1.21 points higher overall, but that difference was not significant.
Personal experience with cancer produced a different pattern. Respondents who had not experienced a cancer diagnosis in a family member scored 1.47 points lower than those who had, while respondents without a cancer diagnosis in a pet scored 1.41 points lower than those who had. Both differences were significant, but they were concentrated among people with lower cancer health literacy; at average and higher ability levels, the groups performed similarly. Individual questions involving inoperable tumors, palliative care and cancer stages showed differences between experienced and inexperienced groups. The investigators caution that some subgroup estimates were imprecise because only a small number of respondents answered certain items incorrectly. For example, the pet-cancer analysis included a group with previous experience, but only two people in that group answered the cancer-stages item incorrectly.
The researchers say the findings could help veterinarians identify owners who may benefit from clearer explanations, teach-back techniques or other communication support, but they do not present the questionnaire as a validated clinical screening tool. The sample came from a single academic veterinary center, was highly educated—70 percent had at least a bachelor’s degree—and was predominantly White or Caucasian, at 93.7 percent. Socioeconomic information was not collected, and the sample was too limited for analyses of differences by race or ethnicity. In addition, more than half of respondents, 879 people or 56.8 percent, reported owning only dogs, raising concerns about the strong performance of the feline leukemia virus question: an incorrect answer might reflect limited cat-specific knowledge rather than low cancer health literacy. Future work must test revised, species-neutral or species-specific versions in larger and more diverse populations. For now, the study’s central message is practical: effective veterinary oncology communication depends not only on the information clinicians provide, but also on how that information functions for owners with different experiences, skills and levels of understanding.
Item response theory is particularly useful when a questionnaire is intended to guide communication rather than simply rank respondents. It treats cancer health literacy as a latent characteristic inferred from response patterns, rather than assuming that every correct answer contributes identical information. In the two-parameter logistic model used here, each question is described by its difficulty and discrimination. A question may be easy overall yet still provide useful information if it distinguishes people near the lower end of the ability continuum. Conversely, a difficult question is not automatically valuable if responses are poorly aligned with the construct being measured.
The distinction between differential item functioning and differential test functioning is important for interpreting the results. DIF flags a question whose response probability differs between groups after accounting for estimated ability; it is therefore a signal for review, not proof that the item is unfair or defective. Differences may reflect vocabulary, numeracy, prior exposure to a clinical setting or genuine differences in relevant knowledge. DTF considers the aggregate effect across the questionnaire. In this study, education-related differences at individual-item level did not accumulate into a statistically significant overall scoring effect, suggesting that the instrument’s total score was more stable across those education groups than some of its component questions.
The findings also illustrate why validation must continue after an instrument has been developed. A questionnaire can have an apparently strong average score while providing limited precision for most respondents if answers cluster near the maximum. Its practical value may instead lie in the lower-ability range, where the study found greater separation between respondents and where communication difficulties may be most consequential. Revisions could therefore focus on replacing redundant, very easy questions with items that probe comprehension without depending unnecessarily on specialist vocabulary or species-specific assumptions. Any revised version would need fresh calibration, because changing wording or content alters item parameters and can change how scores should be interpreted. Testing across different practices, regions, cultural groups and levels of veterinary experience would also help establish whether the observed pattern reflects the questionnaire itself or the particular clientele who completed it.
Subject of Research: Cancer health literacy measurement among dog and cat owners in veterinary oncology
Article Title: Initial implementation of a cancer health literacy questionnaire among owners of pet dogs and cats attending a primary veterinary healthcare service: Part II. Item difficulty and discrimination
Article References: Dixon, A. L., Cernicchiaro, N., Grimes, E., Hocker, S. E., Higginbotham, M. L., & Wouda, R. M. (2026). Initial implementation of a cancer health literacy questionnaire among owners of pet dogs and cats attending a primary veterinary healthcare service: Part II. Item difficulty and discrimination. Veterinary Oncology, 3(1), Article 23. https://doi.org/10.1186/s44356-026-00072-5
Image Credits: AI Generated
DOI: 10.1186/s44356-026-00072-5
Keywords: veterinary oncology, cancer health literacy, pet owners, health communication, item response theory, questionnaire validation, psychometrics, dogs, cats, Initial, implementation, cancer
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Scienmag. “Pet Owners’ Cancer Knowledge Test Exposes Gaps in Veterinary Communication.” Scienmag, 28 August 2026, https://scienmag.com/pet-owners-cancer-knowledge-test-exposes-gaps-in-veterinary-communication/. Accessed 28 August 2026.
Scienmag. “Pet Owners’ Cancer Knowledge Test Exposes Gaps in Veterinary Communication.” Scienmag. August 28, 2026. https://scienmag.com/pet-owners-cancer-knowledge-test-exposes-gaps-in-veterinary-communication/
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