From the Guidelines
Neutrophil and platelet engraftment thresholds after SCT are defined as an absolute neutrophil count (ANC) of >500/mm3 and a sustained platelet count of >20,000, lasting >3 consecutive days without transfusions. These thresholds are critical markers of successful hematopoietic recovery following transplantation, as they indicate the restoration of effective phagocytic function and a decreased risk for bacterial and fungal infections 1. Key factors to consider in the context of engraftment include:
- The timing of engraftment, which can vary depending on the stem cell source, with a median of 22 days after HSCT for unrelated allogeneic recipients 1
- The importance of monitoring for engraftment through daily complete blood counts
- The potential for immune system dysfunction for months after engraftment, including abnormal CD4/CD8 T-cell ratios and immunoglobulin deficiencies 1
- The potential impact of corticosteroid use and CMV infection on engraftment and immune system recovery 1. In clinical practice, achieving these engraftment thresholds is crucial for reducing the risk of infections and other complications, and for improving patient outcomes in terms of morbidity, mortality, and quality of life.
From the FDA Drug Label
The median time to myeloid recovery (ANC ≥500 cells/mm3) in 53 patients receiving LEUKINE was 4 four days less than in 56 patients treated with placebo ANC ≥500 cells /mm3 ANC ≥1000 cells /mm3 A statistically significant reduction in the median number of days of severe neutropenia (ANC < 500/mm3) occurred in the NEUPOGEN-treated groups versus the control group
The engraftment threshold for neutrophils after stem cell transplantation (SCT) is ANC ≥ 500 cells/mm3 and for platelets is ≥ 20,000/mm3 by day 28.
- Neutrophil engraftment is defined as the first of three consecutive days with an ANC ≥ 500 cells/mm3.
- Platelet engraftment is defined as the first day with a platelet count of ≥ 20,000/mm3. 2 3
From the Research
Neutrophil Engraftment Threshold
- The traditional definition of myeloid engraftment is the first of 3 consecutive days with an absolute neutrophil count (ANC) of ≥0.5 x 10^9/L 4.
- However, a study found that the first day with ANC ≥0.5 x 10^9/L is consistently the first of 3 consecutive days with ANC ≥0.5 x 10^9/L in autografted patients, suggesting that the traditional definition can be changed to consider the first day with ANC ≥0.5 x 10^9/L as the day of engraftment 4.
- Novel markers such as mean-volume-neutrophils (MNV) and mean-conductivity-neutrophils (MNC) can predict engraftment 3.8±2.7 days earlier than ANC ≥0.5 x 10^9/L 5.
Platelet Engraftment Threshold
- There is limited information available on the specific threshold for platelet engraftment after stem cell transplantation (SCT) in the provided studies.
- However, a study compared the use of granulocyte colony-stimulating factor (G-CSF) after autologous peripheral blood stem cell transplantation and found no significant difference in time to platelet engraftment between the early and ANC-driven G-CSF groups 6.
G-CSF Administration and Engraftment
- G-CSF administration after SCT can accelerate neutrophil recovery and decrease hospitalization time 7, 8.
- The optimal timing for G-CSF infusion remains unknown, but studies suggest that early initiation of G-CSF (on day +5) and ANC-driven initiation of G-CSF are associated with similar times to neutrophil engraftment and length of stay post-transplantation 6, 7.
- A prospective, randomized trial found that G-CSF accelerates neutrophil engraftment following peripheral-blood stem-cell transplantation, with a median time to neutrophil count ≥500/μL of 10.5 days in the G-CSF group versus 16 days in the control group 8.