Chromosomenegative

Chromosome-negative is a term in cytogenetics and clinical genetics indicating that a targeted chromosomal abnormality is not detected in a sample. The designation is relative to a specific abnormality and does not imply that all chromosomes are normal or that the genome has no anomalies. It is common in hematologic testing and prenatal/postnatal genetics to describe the absence of a tested-for chromosomal change.

In hematology, for example, Philadelphia chromosome-negative status means the BCR-ABL1 fusion is not detected, which affects prognosis and treatment choices. The term can also apply to absence of other tested rearrangements, deletions, or translocations in a disorder or patient.

Detection methods include conventional karyotyping, fluorescence in situ hybridization (FISH), microarray, and molecular assays such as PCR or targeted sequencing. The method chosen depends on the suspected abnormality and required sensitivity.

Negatives must be interpreted with caution. A negative result may reflect true absence, but can also arise from technical limits, low disease burden, sampling issues, or mosaicism. Clinicians integrate results with clinical data and may repeat testing or use a more sensitive assay if indicated.