Analysis of abnormal clones by the fluorescent aerolysin method in paroxysmal nocturnal haemoglobinuria and other marrow disorders.

INTRODUCTION

Flow cytometry is the most sensitive and specific diagnostic modality for the assessment of clone size in paroxysmal nocturnal haemoglobinuria (PNH) and other bone marrow failure states. In this study, we attempt to distinguish PNH from aplastic anaemia (AA) and myelodysplastic syndromes (MDS) associated with PNH clones at diagnosis by clone size, clinical and laboratory features.

METHODS

A total of 29 samples included 19 PNH cases and 10 AA/MDS cases with PNH clones. Flow cytometry was performed using fluorescent aerolysin (FLAER)-based assay and comparison of clinical features, laboratory parameters and PNH clone size was carried out at diagnosis.

RESULTS

The PNH clone size on granulocytes varied from 0.4% to 99.2% and correlated with the clone size on monocytes (r = 0.966; P < 0.001). Paroxysmal nocturnal haemoglobinuria clone size on granulocytes (median = 34.6%) and monocytes (median = 49.9%) was always larger than erythrocytes (median = 10.9%). The median clone size in PNH (median granulocytes = 74.9%, monocytes = 71.8%) was significantly greater than in AA/MDS associated with PNH clone (median granulocytes = 2.9%, monocytes = 6%). In PNH patients, a significant negative correlation was seen between PNH clone on monocytes and the haemoglobin concentration.

CONCLUSION

In our small study using the FLAER method, the clone size was >70% in majority of PNH cases. In other marrow disorders like AA/MDS, the clone size was usually <10%.