Awareness of the range of additional parameters offered by many modern hematology analysers is increasing and some have found applications in today’s clinical diagnostic laboratories. In order to determine the white blood cell (WBC) count and differential, the Advia 120 (Bayer Diagnostics, Tarrytown, NY) uses low angle (0–5°) and high angle (5–15°) light scatter measurements to determine size and density of the cellular nuclei following removal of the cytoplasm by phthalic acid, as well as a cytochemical reaction involving hydrogen peroxide and a substrate (4-chloro-1-naphthol) to measure peroxidase activity in white blood cells. The latter are then displayed visually as 2-dimensional cytograms. The utility of these parameters to provide an early indication of the presence of leukemic cells was assessed retrospectively in 25 newly presenting cases of acute myeloid leukemia (AML) without peripheral blood pancytopenia. Using the French-American-British (FAB) classification, the cases comprised M0 (n=1), M1 (n=2), M2 (n=2), M3 (n=2), M4 (n=1), M5 (a+b) (n=4), and M6 (n=1). The remaining 12 patients were unclassified AML (although not M3). Using the classification system described by d’Onofrio (

Bloodline Reviews
2001
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2-R
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3
–6
), peroxidase activity was scored from P0 (peroxidase negative) to P6 (intense peroxidase positivity), and nuclear density was scored as D0 (normal profile) or D1 (abnormal mononuclear cell population shifted down and to the left - a region corresponding to the presence of blast cells). 23 out of 25 cases were correctly classified as probable AML (92%), comparing well with the findings of d’Onofrio (95.2%). 21 out of these 23 cases were also categorised correctly according to probable FAB type (91%). Of the 2 cases incorrectly classified, 1 case was classified as probable acute lymphoblastic leukemia (ALL), and 1 case was classified as probable myelodysplastic syndrome (MDS). Of note, only cases of M3 AML are allocated to the P6/D1 classification category. Both cases of M3 AML in this study were P6/D1and none of the remaining cases were misclassified into this category. The risk of associated coagulopathy and the unique response to treatment with all-trans retinoic acid (ATRA) makes prompt detection particularly important within this AML patient subgroup. Although not diagnostic in itself, the use of peroxidase activity and nuclear density analysis cytograms in routine complete blood counts (CBC) provides a valuable early indication of a possible case of AML, allowing the prompt initiation of confirmatory tests.

Topics:
leukemia, myelocytic, acute, peroxidase, tretinoin, acute lymphocytic leukemia, blood coagulation disorders, hydrogen peroxide, leukemic cells, myelodysplastic syndrome, naphthols, pancytopenia

Corresponding author

2005, The American Society of Hematology
2005
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