Jim Fairles

Animal Health Laboratory, University of Guelph, Guelph, ON

AHL Newsletter 2020;24(1):2.

It is understood that any diagnostic workup needs to have results that are accurate, meaningful and interpretable as the endpoint. This workup should provide a cost-effective approach (best “bang for the buck”) to solving the problems that are encountered.

More than once, I have heard in our AHL anatomic pathology rounds that the diagnostic outcome would have been better if only “X” had been done. It behooves us all to make sure that we adhere to the best “diagnostic standard of care” (1) and minimize diagnostic errors when possible.

Listed below are some common questions and issues that we encounter.

• To test or not to test: will the test results be used to direct a change or take an action? This thought process can become complex as it may take more than a single test to establish a pattern from “normal”.
• Samples numbers: this is especially important in population medicine to provide confidence with a diagnosis or confirm freedom from disease.
• Avoiding common diagnostic errors:
  • Point of care and in-clinic testing - while these can provide valid, rapid answers, please keep in mind all of the issues around sample integrity, calibration, maintenance and quality control.
  • Insufficient information - no history provided on the submission form. This precludes our laboratory diagnosticians from getting involved and helping with the interpretation of diagnostic results. The complete medical history is not necessary, just a brief summary of your thought process around the case.
  • Wrong sample submitted - we are always available to consult if you have questions!
  • Sample degradation - the cold chain (hot vs cold weather), spinning serum samples, including EDTA blood smears, using virus transport media.  These are just some examples to help mitigate deterioration of samples that interfere with laboratory testing.
  • Selecting tests that are not “fit for purpose” - antigen vs antibody testing and biology-related issues that affect sensitivity and specificity. Please consult us if unsure which test is best suited for the diagnostic outcome that you are seeking.
  • Sample selection - consult the AHL Users’ Guide and diagnostic plans. A full set of formalin-fixed and fresh tissues increases diagnostic success. Fresh tissues can be held at the laboratory until preliminary histopathology results direct appropriate microbiologic analysis, thereby decreasing overall testing cost.

We encourage you to contact us and discuss your disease investigation so that we may assist you in getting the most out of your diagnostic laboratory submissions.  AHL

Reference

1. Thompson BS. On the journey for great diagnostics – Tips and tricks to let the magic happen. AABP, St. Louis, Sept. 2019.