Hot Topic

Common Test-Ordering Errors
Part 2: Misordered Tests

T & B Cells

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Published: May 2010

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Dr. Dale reviews test-ordering errors commonly seen at Mayo Medical Laboratories. This is the second presentation in the series and addresses the misordered tests for T and B cells.

Presenter: Jane C. Dale, MD

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Transcript

Introduction

Welcome to Mayo Medical Laboratories' Hot Topics. These presentations provide short discussions of current topics and may be helpful to you in your practice.

Our presenter for this 8-part series is Dr. Jane Dale, a consultant in the Department of Laboratory Medicine and Pathology at Mayo Clinic. Dr. Dale reviews test-ordering errors commonly seen at Mayo Medical Laboratories. This is the second presentation in the series and addresses the misordered tests for T and B cells.

Testing at Mayo Medical Laboratories

Here at Mayo Medical Laboratories we receive over 800,000 test orders each month. While by our estimation most of the orders we receive are appropriate orders, we do experience some recurring test-ordering problems. In this presentation, I will describe the most common problems that we see. I will also describe our efforts to decrease these problems and recommend ways that you too can help reduce these errors. Together, by decreasing inappropriate test orders, we can improve patient care and reduce costs.

Common Mayo Medical Laboratories Test-Ordering Errors

In this 8-part series, I will address 2 types of errors - misordered tests and overordered tests.

Misordered Tests

In the first parts of the presentation I will discuss misordered tests, that is, tests that are mistakenly ordered for the wrong purpose. This is a list of the most commonly misordered tests received by Mayo Medical Laboratories. In part 1, we discussed 3 chemistry tests--1,25-dihydroxyvitamin D, PTH-related peptide, and uroporphyrinogen III synthase. In part 2, we will discuss the most commonly misordered flow cytometry tests that measure T and B cells.

T- & B-Cell Tests by Flow Cytometry

We offer an array of T- and B-cell tests, ranging from those that measure only a few cell types to tests that quantitate and characterize many cell types and their subsets. In our experience, 3 of these tests are frequently misordered, providing more information than is necessary to manage the patient.

CD4 Count for Immune Monitoring, Blood (#84348)

We have a test for monitoring AIDS patients—“CD4 Count for Immune Monitoring.” This test measures only T cells and is sufficient for patients with AIDS, because it is the T-cell population of lymphocytes that is targeted by the AIDS virus, and T-cell counts play a key role in making the diagnosis, determining treatment, and following the course of the disease.

T- and B-Cell Quantitation by Flow Cytometry (#9336)

But we have found that another test, “T- and B-Cell Quantitation by Flow Cytometry,” is often ordered for AIDS patients. This test, which measures both T and B cells, is often ordered when the more focused and less expensive test of the T cells would suffice. “T- and B-Cell Quantitation” should be ordered when quantitative information is required on both B and T cells. It is a second-order test when evaluating patients with possible immunodeficiency states.

B-Cell Phenotyping Profile for Immunodeficiency and Immune Competence Assessment, Blood (#88800)

Next on our list is “Immune Assessment B Cell Subsets.” This is a large profile that includes the “T- and B-Cell Quantitation” test just discussed, plus 9 other B-cell markers, as well as an additional reflex test, if indicated.

Indications for Ordering #88800

Test #88800 should only be ordered if very detailed B-cell subset information is needed. Clinical examples of this include:

  • Common variable immunodeficiency: a primary immunodeficiency with a prevalence of 1:25,000 to 1:50,000
  • Hyper-IgM syndromes
  • Assessing B-cell subset reconstitution after stem cell or bone marrow transplant
  • Assessing response to B cell-depleting immunotherapy

In most other non-AIDS situations, “T- and B-Cell Quantitation by Flow Cytometry” is sufficient.

In the 3 examples that I just discussed, we are investigating T- or B-cell deficiencies (that is, situations with low cell counts).

Leukemia/Lymphoma Immunophenotyping (#3287)

But, flow cytometry is also used to diagnose hematologic malignancies. In such situations, cell counts are increased and a variety of cell markers may be required to accurately characterize the malignancy and determine appropriate therapy. Thus, a different test is indicated—“Leukemia/Lymphoma Immunophenotyping” is the blood test for increased counts and hematologic malignancies.

We want to make sure that your physicians get the information they need, but are not overloaded with additional information that is unnecessary for that particular patient. When you review the components of the various T- and B-cell tests that we offer, you can see how information overload can occur if the wrong test is selected. These more extensive tests are more expensive and we want to ensure that patients and insurers do not have to pay for larger test panels than are needed.

Because selecting the correct tests for T and B cells can be tricky, I encourage you to review our test information in our electronic test catalog. When questions arise, our physicians and laboratory scientists are available to help you select the appropriate test for your patient by calling our customer service center.

Conclusion

This concludes Part 2 of this series on some of the tests that, in our experience as a reference laboratory, are commonly ordered inappropriately.


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