64
ICCS 2011
P28
Experience with a High Sensitivity Flow
Cytometric Assay for Detection of Paroxysmal
Nocturnal Hemoglobinuria Clonal Populations.
Charles F. Repetti, Vanessa A. Jones, Daniel M.
Jones
Quest Diagnostics Nichols Inst, Chantilly, VA, USA
New guidelines for the diagnosis and monitoring
of PNH have been recently promulgated that
recommend use of high sensitivity testing of erythroid,
granulocytic or monocytic lineages (Borowitz, M
et al. Cytometry 78B 211:230 2010). We compare
here the detection rate of PNH clones using such a
high sensitivity assay (0.01%) with an older assay
with lower sensitivity (1%). Erythrocytes are stained
with Glycophorin A-FITC + CD59-PE and 250,000
cells are collected. WBCs are stained with a 6
color panel, including FLAER, CD24, CD16, CD33,
CD14, and CD45. Samples from 16 patients being
evaluated from PNH were tested with the old assay
compared to samples from 40 patients with the new
assay. Patient ages range from 11 – 90 years, with
a male/female ratio =0.86. Using the new assay, 10
patients (25%) showed minor PNH clones which
were below the sensitivity of the older assay with
clonal size for neutrophils ranging from 0.05% to
98.8% (mean 44.89% ). Clonal types found were:
Type III only: n=35; Type II only: n=6; Type III +
Type II: n=14; single Type III + double Type II: 1. No
relation between age and clonal size was evident.
The ratio of clonal sizes for neutrophils vs. monocytes
within a patient was similar (r2=1.13), suggesting
that monocytes can be of value in confrming status
in cases with MDS-associated (or other) aberrant
granulocyte immunophenotypes. Higher sensitivity
rates for PNH diagnosis and monitoring will reveal a
signifcant number of low-level PNH clones in routine
clinical samples.
POSTER ABSTRACTS