Laboratory Test Reference Guide

A CBC must be performed at the same time as a HPC Test.

Send at 4°C

See interpretive comment below.

The current method of guiding stem cell harvests is to perform flow cytometry (CD34) for all patients. A stem cell harvest is performed every 1 to 2 weeks on ward M5. A patient undergoing a stem cell harvest may need CD34 quantitation by flow cytometry once or up to 4 consecutive days depending on the harvest yield. CD34 testing, although it is the gold standard test is laborious, time consuming, expensive and requires special skill which limits it's availability.

The Sysmex XN 9000 automated haematology analyser (Haematology Department - Laboratory) has a WPC (white cell precursor) channel that can enumerate HPCs (haematopoietic progenitor cell) in peripheral blood by gating on a different population using the principles of fluorescent flow cytometry. By using this test to triage whether or not flow cytometry is required when patients have autologous stem cell harvests, we can avoid performing flow cytometry on a significant proportion of these patients. A verification cohort (65%) has showed that positive and negative HPC cut-offs can avoid processing flow cytometry safely on the majority of patients undergoing stem cell harvests. HPC assessment is quick, cheap and can be performed by a routine scientist/technician. It is thus preferable to use HPC where possible instead of flow cytometry. 

HPC ≤ 5.3 cells/mcL – Correlates with CD34 <10 cells/mcL thus predicts an inadequate stem cell yield. It is advised to not proceed with stem cell apheresis. It may be appropriate to optimise adjunctive mobilising medications. 

HPC 5.4 – 17.2  cells/mcL – Indeterminate HPC result that did not meet negative or positive cutoffs in validation cohort. Correlate and be guided by CD34. 

HPC ≥ 17.3 cells/mcL – Correlates with CD34>20 cells/mcL and predicts a good harvest. Proceeding with stem cell apheresis is recommended. 

1 mL EDTA (purple)