Disparity in the detection of chromosome 15 centromere in patients of African ancestry with a plasma cell neoplasm.

PURPOSE

Fluorescence in situ hybridization (FISH) is the current gold standard assay that provides information related to risk stratification and therapeutic selection for individuals with plasma cell neoplasms. The differential hybridization of FISH probe sets in association with individuals' genetic ancestry has not been previously reported.

METHODS

This retrospective study included 1224 bone marrow samples from individuals who had an abnormal plasma cell proliferative disorder FISH result and a concurrent conventional G-banded chromosome study. DNA from bone marrow samples obtained from the G-banded chromosome study was genotyped, and a biogeographical ancestry prediction was carried out.

RESULTS

Using a cohort of individuals with a plasma cell neoplasm, we identified reduced hybridization of a chromosome 15 centromere FISH probe (D15Z4). Metaphase FISH studies of cells with 2 copies of chromosome 15 demonstrated a failure of the D15Z4 FISH probe to hybridize to one chromosome 15 centromere, revealing a false-positive monosomy 15 FISH result in some individuals. Surprisingly, individuals with a monosomy 15 FISH result had a median African ancestry of 77.2% (95% CI 74.1%-80.3%), compared with a median African ancestry of 2.2% (95% CI 2.0%-2.5%) in the non-monosomy 15 cohort ( value = 9.4 × 10). Thus, individuals with African ancestry had an 8.02-fold (95% CI 3.73-17.25) increased probability of having a false-positive monosomy 15 result ( value = 9.92 × 10).

CONCLUSION

This study emphasizes a concern regarding the reliability of diagnostic genomic tools and their application in interpreting genetic testing results in diverse patient populations. We discuss alternative methodologies to better represent different ancestry groups in clinical diagnostic testing.