Interpretation by clinicians of probability expressions in cytology reports and effect on clinical decision-making

Cytology often is used to obtain a diagnosis, such as that of malignant neoplasia. When a diagnosis is uncertain, pathologists often express probability using qualitative terms, such as "probable," that have imprecise meanings.

Terms expressing probability are interpreted variably by veterinary practitioners and affect decisions regarding treatment and euthanasia.

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An online survey of members of the Veterinary Information Network was conducted. Veterinarians were asked to assign percentage probabilities to 18 modifiers of a diagnosis of lymphoma. They also were asked to select their most likely clinical action based on a diagnosis of lymphoma qualified one of 4 modifiers. Results were analyzed using descriptive and nonparametric methods. Percentage probabilities were analyzed by ANOVA after variance stabilization.

For 871 valid surveys, probabilities assigned to the 18 modifiers overlapped substantially, with medians (interquartile range) of 50% (50-70%) for "possible," 66% (66-85%) for "probable," and 70% (70-90%) for "consistent with." More (P < .001) veterinarians (50.4%) chose to initiate treatment with a diagnosis of "consistent with lymphoma" as compared with "probable" (14.6%) or "possible" (1.6%) lymphoma. For clients considering euthanasia if the diagnosis was cancer, more (P < .001) veterinarians recommended euthanasia with a diagnosis of "consistent with lymphoma" (62.5%) as compared with "probable" (35.3%), or "possible" (2.0%) lymphoma.

Probability expressions are interpreted variably yet have a major impact on clinical decision-making, including the decision to recommend euthanasia. Standardized terminology could improve decision-making and enhance clinical outcome.