Incorrect measurement of leukocyte counts in post-bone marrow transplantation (P-BMT) patients

Excerpt

Recent hematological analyzers [1] can measure a very small number of leukocytes (10/μl), but some types of analyzers do not wash the detection chamber between each measurement. Leukocyte carryover is negligible in hematological analysis for patients with large numbers of leukocytes (>1000/μl) [2]. However, there is no study investigating leukocyte carryover in patients with small numbers of leukocytes (<500/μl). Recently, the number of patients with leukocytopenia has been increasing as intensive therapies such as post-bone marrow transplantation (post-BMT) and chemotherapy prevail. Therefore, we examined the effect of leukocyte carryover on the measurement of leukocyte number in patients with post-BMT. Ethylenediaminetetraacetate (EDTA)-2K-anticoagulated venous blood samples were obtained from specimens sent to the hematology laboratory for routine testing. Using the hematological analyzer Sysmex NE-8000 (Kobe, Japan) with the impedance method, we examined the reproducibilities of measurements of small numbers of leukocytes from seven post-BMT patients by washing the detection chamber between each measurement. Furthermore, we examined the effect of leukocyte carryover on the measurement of a small number of leukocytes from three post-BMT patients by not washing the detection chamber after measurement of each routine sample. Standard deviations (SDs) of the measurements of a small number of leukocytes (means: 20/μl–400/μl) from seven post-BMT patients were very small (10/μl–20/μl) when we washed the detection chamber between each measurement. Therefore, the washing procedure facilitates correct and stable measurement of small numbers of leukocytes in the hematological analyzer. Without the washing procedure between each measurement, however, the numbers of leukocytes from three post-BMT patients increased after measurement of routine samples (Table 1). The effect of leukocyte carryover was larger in routine samples with larger numbers of leukocytes (Table 1). …