Value of CD16/CD66b/CD45 in comparison to CD55/CD59/CD45 in diagnosis of paroxysmal nocturnal haemoglobinuria: An Indian experience

BACKGROUND & OBJECTIVES: Diagnosis of paroxysmal nocturnal haemoglobinuria (PNH), a rare haematopoietic stem cell disorder, is challenging in patients with bone marrow failure (BMF) syndrome like aplastic anaemia (AA). This study was conducted with the aim to test the efficacy of the newly recommended markers viz. anti-CD16 and CD66b antibody over the existing anti-CD55 and CD59 antibody for PNH diagnosis in India. METHODS: This study was conducted on 193 suspected cases of PNH by flow cytometry using lyse wash technique to stain the granulocytes with CD16/CD66b and CD55/CD59. RESULTS: Of the 193 suspected cases, 62 patients showed the presence of PNH clone. Forty six patients were detected by CD55/CD59/CD45, whereas 61 were detected by CD16/CD66b/CD45. CD16/CD66b detected 16 (25.8%) additional patients over CD55/CD59 (P<0.05) and was more sensitive in detecting the PNH clone with higher negative predictive value. Most of the patients (11/16) who were picked up by CD16/CD66b were of AA who had small clone sizes. Further, the PNH clones were more discreetly identified in CD16/CD66b plots than by CD55/CD59. Clone size assessed by CD16/CD66b which reflects the clinical severity of classical PNH (thrombosis/haemolysis), was more representative of the underlying clinical condition than CD55/59. INTERPRETATION & CONCLUSIONS: In our experience of 62 patients of PNH, CD16/CD66b proved to be more efficacious in detecting PNH. The new panel was especially useful in monitoring PNH associated with BMF which had small clone sizes.