• Diagnose acute myelomonocytic leukemia (AML) with abnormal eosinophils, with inv(16) or t(16;16) (ie, CBFB/MYH11)

• Monitor effectiveness of treatment

• Monitor minimal residual disease (MRD)

• Predict early relapse

The pericentric inversion of chromosome 16(p13;q22), and less frequently the t(16;16) (p13;q22) translocation, accounts for 16% of the chromosomal aberrations associated with AML. This inversion results in fusion of the core binding factor β (CBFB) gene on 16q22 with the smooth muscle myosin heavy chain gene (MYH11) on 16p13, leading to the formation of a chimeric CBFB/MYH11 fusion protein. Clinically, the inv(16) or t(16;16) is associated with AML with abnormal eosinophils (French–American–British classification M₄E₀ subtype), with abnormal eosinophils being part of the malignant clone. Patients with inv(16) or t(16;16) generally have relatively good response and long-term disease-free survival rates.

The quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) assay for CBFB/MYH11 can be used as a sensitive tool for diagnosis of AML subtype M₄E₀, monitoring of MRD, and assessment of the potential for disease relapse during and after chemotherapy.

This quantitative real-time RT-PCR method utilizes primers to amplify the CBFB/MYH11 fusion transcript. Amplification of the ABL gene transcript is performed as a control for sample RNA quality and as a reference for relative quantification. Results are reported as positive or negative; if positive, the ratio of CBFB/MYH11 to ABL transcript amplification is reported. The current specimen will be tested side-by-side with a previous sample, if available, to monitor the quantitative change with time (trend).

This assay can detect 1 tumor cell in 100,000 cells.

Positive results are indicative of AML subtype M₄E₀. Results are reported as the ratio of amplified fusion product from the patient sample to that of the internal control. For monitoring MRD, we recommend monitoring changes with time (trend) rather than the absolute ratio of a single measurement.