The effects of 99mTc-HMPAO-labelled leucocyte scan on human karyotype

Technetium-99m hexamethylpropylene amine oxime (HMPAO) white blood cell scan (WBCS) requires separation and labelling of mixed leucocytes, which include particularly radiosensitive cells, lymphocytes. Lymphocytes labelled during the mixed leucocyte labelling procedure could represent a problem for patients owing to the possible induction of chromosomal aberrations. Lymphocytes labelled in mixed leucocyte preparations are probably killed by the high-dose radiation. Nevertheless, it has been reported that some of these lymphocytes can proliferate after in vitro stimulation. If these cells were to reproduce themselves in vivo, onset of, or increase over time in, chromosomal aberrations could occur on peripheral blood lymphocytes. The present study was performed on 21 patients who underwent WBCS for suspected infection/inflammation. Blood samples of these patients were submitted to cytogenetic study, comprising karyotype determination, evaluation of sister chromatid exchanges (SCE) and evaluation of induced chromosomal breakages or rearrangement rate (B/R). This study was performed 2 h before and 7 days and 6 months after the WBCS. The results demonstrated no statistically significant differences between SCE and B/R values before and after WBCS. No cause-effect relationship appeared to exist between WBCS and the onset of chromosomal aberrations in peripheral blood lymphocytes, at least during the first 6 months post WBCS and within the limits of this study's approach. The high-dose radiation administered to lymphocytes was almost certainly sufficient to kill these cells.