2005 Scientific Session Abstracts
Terminology Used to Express Diagnostic Probability in Cytopathology: Interpretation by Veterinary Clinicians and Effect on Clinical Decision-Making
Mary M. Christopher, DVM, PhD (mmchristopher@ucdavis.edu) 1; Christine S. Hotz, DVM, MS 2; Sonjia M. Shelly, DVM 3; Paul Pion, DVM 4. 1School of Veterinary Medicine and 2School of Medicine, University of California-Davis; 3IDEXX Veterinary Laboratories, West Sacramento, CA; 4Veterinary Information Network, Davis, CA
Context : Fine-needle aspiration cytology often is used to obtain a diagnosis of lymphoma in dogs. When chemotherapy is not an option, the client may elect euthanasia for their pet. In a previous study, veterinary clinical pathologists were found to use a wide variety of terms to express the probability of a cytologic diagnosis. Such terms have imprecise meanings that may affect interpretation and clinical decisions.
Technology : A web-based survey was provided during Sept-Dec 2004 to veterinary clinicians enrolled in the Veterinary Information Network. Results were analyzed statistically using ANOVA following variance stabilization and nonparametric techniques.
Design : The survey included: A) demographic information; B) assignment of percentage probabilities to 18 modifiers of a positive diagnosis of lymphoma; and C) selection of a “most likely” clinical action based on diagnoses modified by probability terms. Results for (B) were compared with those obtained previously from veterinary pathologists.
Results : Respondents were veterinarians in general practice (86.4%), specialty practice (9.4%), and veterinary schools (4.2%).
Table. Probabilities assigned to modifiers by veterinary clinicians compared with pathologists.
Cytologic Diagnosis |
Clinicians (n = 740) |
Pathologists (n = 90) |
P |
Median (10-90 thpercentile) |
Median (10-90 thpercentile) |
||
Diagnostic for lymphoma |
99 (80-100) |
100 (95-100) |
.0001 |
Consistent with lymphoma |
80 (60-99) |
85 (70-95) |
.0015 |
Probable lymphoma |
75 (50-90) |
80 (60-90) |
.1463 |
Suggestive of lymphoma |
75 (50-90) |
75 (60-88) |
.1230 |
Possible lymphoma |
50 (40-75) |
50 (34-75) |
.3358 |
No evidence for lymphoma |
10 (0-90) |
5 (0-38) |
.0071 |
Clinicians were 3X more likely to initiate treatment with a diagnosis of consistent with- as compared to probable-; and 31X more likely to initiate treatment with a diagnosis of probable- as compared to possible-. For clients electing euthanasia if the diagnosis was cancer, clinicians were 2X as likely to recommend euthanasia with a diagnosis of consistent with- as compared to probable-; and ~18X as likely to recommend euthanasia with a diagnosis of probable- as compared to possible-. About 12% of clinicians indicated they usually ignore any descriptive terms altogether.
Conclusions : Veterinary clinicians are highly variable in their interpretation of probability expressions. Probability terms have a major impact on clinical decision-making, including the decision to euthanize pets.