Clinically the patients have
(1) pancytopenia
(2) moderate to severe splenomegaly
(3) usually no lymphadenopathy.
Splenectomy is performed in patients with severe pancytopenia in order to reverse the low cell counts by reduction of splenic sequestration, but not all patients show adequate post-operative cell counts. One explanation for this failure to respond is that severe bone marrow involvement by tumor reduces marrow production of the normal cellular elements.
hairy-cell index (HCI) =
= ((decimal fraction of bone marrow that is cellular) * (decimal fraction of marrow cellularity that is hairy-cells)
where:
• Each decimal fraction is a number between 0 and 1.
• The index is a number between 0 and 1.
Interpretation:
• If a post-splenectomy platelet count of 200,000 /µL is defined as a satisfactory post-splenectomy platelet count, the pre-operative HCI correlates with the frequency of a satisfactory post-splenectomy platelet count.
|
HCI
|
% with Satisfactory Post-Splenectomy Platelet Counts
|
|
<= 0.50
|
81%
|
|
0.51 - 0.69
|
52%
|
|
>= 0.70
|
40%
|
Significance:
• A patient who has a HCI >= 0.7 and who does not show a satisfactory platelet count after splenectomy may be a candidate for early intervention with low-dose chemotherapy.
