AML1 / ETO t(8;21) Quantitative |
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Test Highlights |
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Clinical Use
| • | Diagnose acute myeloid leukemia (AML) with t(8;21) chromosome translocation |
| • | Monitor treatment response |
| • | Monitor minimal residual disease (MRD) |
| • | Predict early relapse |
Clinical Background
The translocation t(8;21)(q22;q22) is one of the most common structural chromosomal aberrations in patients with AML, occurring in about 15% of adult AML cases and 40% of AML cases with differentiation (AML-M2). AML with t(8;21) has a mean onset age of about 30 years and is most common in children and younger adults; it is relatively rare in elderly patients. The presence of t(8;21) is associated with the highest complete remission rate (90%) and the highest probability (50%-70%) of remaining in complete remission at 5 years. However, the disease may become resistant to therapy upon relapse.
Translocation t(8;21)(q22;q22) fuses the 5'-portion of the AML1 gene on chromosome 21 to the almost complete open reading frame of the ETO gene on chromosome 8. Thus, the transactivation domain in the middle of AML1 is replaced with part of the ETO. This results in constant expression of AML1/ETO fusion mRNA, which can be detected by reverse transcription-polymerase chain reaction (RT-PCR). The quantitative t(8;21) assay can be used not only to diagnose AML, but also to serially monitor patients for MRD, evaluate the effectiveness of treatment, and predict early relapse.
Method
In this real-time quantitative RT-PCR assay, the AML1-ETO fusion transcript and an internal control (ABL transcript) are amplified from the same RNA sample. The internal control serves as a control for real-time PCR performance and as a reference for relative quantitation; the relative ratio of AML1-ETO to internal control is reported. The current sample will be tested side-by-side with a previous stored sample, if available, to monitor quantitative changes with time (trend). This assay can detect 1 leukemic cell in a background of 105 normal cells. There is no known cross-reaction with other AML translocations.
CPT Codes:* 83891, 83898 x2, 83896 x2, 83902 x2, 83912
Interpretive Information
If the AML1-ETO (t[8;21]) translocation is detected, the result will be reported as positive and the ratio will be provided. Higher ratios are associated with higher percentages of leukemic cells. A negative result (a ratio of zero) indicates absence of the AML1-ETO translocation.
For monitoring MRD, we recommend monitoring trends rather than the absolute ratio of a single measurement.
Specimen Requirements
3 mL room-temperature or refrigerated whole blood in an EDTA (lavender-top) tube; ACD (yellow-top) whole blood is also acceptable.
Alternatively, submit 3 mL bone marrow.
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This test was developed and its performance characteristics determined by Quest Diagnostics Nichols Institute. It has not been cleared or approved by the U.S. Food and Drug Administration. The FDA has determined that such clearance or approval is not necessary. Performance characteristics refer to the analytical performance of the test.
* The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.
Polymerase chain reaction (PCR) is performed pursuant to a license agreement with Roche Molecular Systems, Inc.
