Utilization of Cytogenetic Testing in Acute Myeloid Leukemia

From the 2018 HVPAA National Conference

Mark Girton (University of Virginia School of Medicine), Eli Williams (University of Virginia School of Medicine)

Background

Cytogenetic testing is performed at various time points for patients with acute myeloid leukemia (AML) to monitor treatment response and for restaging. At the University of Virginia (UVA), the increased demand for cytogenetic and molecular testing led us to evaluate the utility of repeat genetic testing over the disease course.

Objectives

The UVA cytogenetics lab typically performs fluorescence in situ hybridization (FISH) for new and repeat AML testing, using probes specific for nine genetic abnormalities. Karyotyping is also performed in the majority of these workups. We sought to determine if a complete FISH panel (nine probes) was warranted for repeat testing of AML or if a personalized, focused FISH panel would provide the same clinical sensitivity while using less resources.

Methods

Cytogenetic chart reviews were performed on all patients tested by the UVA cytogenetics laboratory that had a cytogenetics study in 2016 and had at least one prior cytogenetics study (n=31). The frequency of new cytogenetic abnormalities detected by karyotype and FISH analysis was monitored over the course of each patient’s disease.  The ability of our standard cytogenetic workup to detect these abnormalities was compared to a focused cytogenetic workup consisting of a karyotype and a focused FISH panel, or a karyotype alone if cytogenetically normal at initial workup. The focused AML FISH panel was selected for each patient based on their cytogenetic workup at diagnosis.

Results

42% (13/31) of AML patients meeting criteria for this study were cytogenetically normal at initial workup. Ten of these patients remained normal in all subsequent studies by both karyotype and FISH, while three showed cytogenetic evolution. The remaining 18 patients presented with cytogenetic abnormalities detectable by FISH.  The focused workup detected disease in 100% of subsequent studies for these patients.

Conclusion

The focused AML FISH panel detects disease with the same efficacy as the full AML FISH panel in the setting of residual disease. Six of 31 patients studied had cytogenetic evolution and all new findings were detected with conventional karyotype.  This indicates that pairing the focused FISH panel with karyotype reliably detects disease.  Based upon these results, the proposed testing algorithm will indicate karyotype only for monitoring disease in patients with initially normal cytogenetics and the focused AML FISH paired with karyotype to monitor patients with initially abnormal cytogenetic studies.  Reflex to the full AML FISH panel may be indicated in the context of a new complex karyotype or clinical restaging.

Implications for the Patient

ing the focused workup as proposed would have saved up to $514,226 in laboratory cost for the 31 patients studied as well as significant laboratory time and resources.  Appropriate test utilization allows the laboratory to devote limited resources to improving care for all patients served.

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