Predictors of the yield of mobilized peripheral blood CD34

Predictors of the yield of mobilized peripheral blood CD34

⁺

cells in HLA-matched sibling donor

S.A.W. Fadilah

^a,b,⇑

, M.I. Mohd-Razif

^a

, Z.A.Z. Seery

^a

, T. Nor-Rafeah

^a,b

, W.J. Wan-Fariza

^a,b

, A. Habsah

^c

, C.F. Leong

^d

aCell Therapy Centre, Kuala Lumpur, Malaysia

bDepartment of Medicine, Kuala Lumpur, Malaysia

cDepartment of Diagnostic Laboratory Services, Kuala Lumpur, Malaysia

dDepartment of Pathology, Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, Malaysia

a r t i c l e i n f o

Article history:

Received 21 May 2013

Received in revised form 23 July 2013 Accepted 29 July 2013

Keywords:

Healthy donors

Peripheral blood CD34⁺cell count Peripheral blood stem cell (PBSC) mobilization

a b s t r a c t

We examined the donor factors that may affect the yield of peripheral blood stem cell (PBSC) mobilized from healthy donors. Pre-apheresis PB-CD34⁺cell count was the only fac- tor that correlated with PBSC yield. Leukocyte count (LC) and monocyte count (MC) corre- lated with PB-CD34⁺cell. Male gender and PB-CD34⁺cell count of at least 87.1/lL and 69.8/

lL on day-4 and -5 of G-CSF were associated with the ability to harvest at least 510⁶/kg CD34⁺cells after one apheresis. We concluded that gender and PB-CD34⁺cell count are important predictors of PBSC yield. LC and MC may serve as surrogate markers for estimat- ing the PB-CD34⁺cell count.

Ó2013 Elsevier Ltd. All rights reserved.

1. Introduction

Peripheral blood stem cells (PBSCs) mobilized from healthy donors is now the preferred source of hematopoi- etic stem cells (HSCs) because of the relative ease of collec- tion, avoidance of general anesthesia, faster hematopoietic engraftment and more potent graft vs malignancy effects [1–3].

The numbers of PBSC infused significantly influenced the outcome of PBSC transplantation[4,5]. Previous studies [6,7]suggested that a minimum of 210⁶CD34⁺cells/kg of recipient body weight are required to achieve hemato- poietic engraftment, while a higher doses of CD34⁺ cell (above 510⁶CD34⁺cells/kg) have been associated with faster neutrophil and platelet engraftment [8–10]. Most

transplant centers utilize a threshold dose of 2–510⁶ CD34⁺ cells/kg as a goal for apheresis in healthy donors, and in our center, we aimed to harvest at least 510⁶ CD34⁺cells/kg from one to three cycles of apheresis. Gran- ulocyte colony-stimulating factor (G-CSF) is the standard mobilizing agent used to harvest PBSC. It has the advan- tage of being relatively safe and tolerated[11]and associ- ated with a predictable peak of CD34⁺ cells in the peripheral blood (PB) between day-4 and -5 of dosing [12,13]. However, there seems to be a wide variation in the yield of CD34⁺ cells obtained from healthy donors mobilized by G-CSF.

Poor mobilization is currently defined as collection of

<210⁶CD34⁺cells/kg, which may be associated with de- layed or failure of hematopoetic engraftment[14,15]. Poor mobilizers may represent up to 20% of healthy donors[16]

resulting in the need for additional apheresis or mobiliza- tion cycle or resorting to bone marrow harvesting.

Prior studies[12,17–21]have reported conflicting data regarding the effects of donor demographic and laboratory factors and apheresis procedure factors on total CD34⁺ 1473-0502/$ - see front matterÓ2013 Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.transci.2013.07.032

⇑Corresponding author. Address: Cell Therapy Centre, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Bandar Tun Razak, 56000 Cheras, Kuala Lumpur, Malaysia. Tel.: +60 3 9145 6449; fax: +60 3 9145 6679.

E-mail address:sfadilah@ppukm.ukm.edu.my(S.A.W. Fadilah).

Contents lists available atScienceDirect

Transfusion and Apheresis Science

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / t r a n s c i

cells yield after apheresis. As such, currently there are no specific well-accepted factors for identifying a potential poor mobilizer among healthy donors mobilized with G- CSF. Donor gender, weight, ethnicity and total dose of G- CSF are important factors in determining the yield of PBSC [12,18,22]. Suzuya et al.[17]showed only age, pre-apher- esis platelet count (PC) and circulating CD34⁺cells on day- 2 after G-CSF injection were significantly associated with PBSC yield.

This study aims to gain insight into the donor factors that may affect the yield of PBSC mobilized from healthy donors among the local Malaysian population.

2. Methods 2.1. Donors

A total of 84 healthy HLA-matched sibling donors who underwent PBSC harvesting in UKM Medical Center within a period of 10 years were included in this retrospective analysis. The study was approved by the institutional eth- ics committee. Informed consent for PBSC donation was obtained before the procedures.

2.2. PBSC and mobilization and collection

For PBSC mobilization, G-CSF (filgrastim; Roche, Basel, Switzerland) was administered subcutaneously at a dose of 10

l

g/kg of donor’s body weight daily[12,17,23]until completion of apheresis. From the third day after started G-CSF injection, PB samples were taken at 8 am from the donors for full blood counts and CD34⁺cells enumeration until completion of apheresis. The first apheresis for PBSC collection was initiated after 4 doses of G-CSF using the COBE Spectra (Cobe Laboratories, Gloucester, UK) and apheresis was repeated daily (up to 6 doses of G-CSF injec- tion) until the targeted CD34⁺cell ofP510⁶/kg recipient body weight has been obtained. The circulatory system was accessed via the femoral vein using a central venous catheter[24]. An apheresis was programmed to process two times the total blood volume and usually took about 4 h to complete. We did not practice the large volume leuk- apheresis protocol in our donors mainly due to the difficul- ties to increase the inlet flow rate beyond 40 mL/min in majority of our donors and to keep the harvesting time around 4 h to avoid unnecessary adverse effects of the har- vesting procedure.

2.3. CD34⁺cell enumeration by flow cytometry

CD34⁺cell enumeration was performed using FASCali- bur flow cytometer (Becton-Dickson, San Jose, CA) with monoclonal anti-CD34⁺ antibody as previously described [25]. In brief, 50

l

L of apheresis product was incubated with 20

l

L of CD34⁺reagent (ProCOUNT kit; BD, San Jose, CA) in an individual bead-containing TruCOUNT tube. The number of CD34⁺cell counts was analyzed using the mod- ified ISHAGE strategy and the ProCOUNT software pack- ages (BD). At least 60,000 of CD45⁺ events and 3000 of

BD TruCOUNT beads were acquired from each sample to ensure accuracy of the analysis[26].

The absolute and total numbers of CD34⁺cells were cal- culated by the following formula:

Absolute CD34⁺cells per microliter No:of CD34^þcells

No:of beads countedNo:of beads per TruCOUNT tube sample volume

Sample dilution factor

Total CD34^þcell countðYieldÞ

Total CD34^þcell count in¼Absolute CD34^þcells=

l

L total product volume

2.4. Statistical analysis

The statistical software package SPSS-version-19.0 was used to perform the data analysis. Data was tested for nor- mality using the Shapiro–Wilk test. Continuous data were compared using independent-sample t-test for normally distributed data and Mann–Whitney-U test for not nor- mally distributed data, while categorical data were com- pared using the Fisher exact test. Variables that were significant in univariate test were evaluated by stepwise logistic regression.

Associations between PB-CD34⁺ cell count and CD34⁺ cell yield and donor factors were assessed by the correla- tion test. Multivariate analysis was performed using linear regression to determine independent donor factors based on factors having significance in univariate analysis. AP value below 0.05 was considered to be statistically significant.

3. Results

3.1. Donors and apheresis data

The donor and apheresis data are shown in (Table 1).

Apheresis was commenced after 4 days of G-CSF in the majority (96.4%) of donors, which coincides with the high- est PB-CD34⁺ cell counts. Three of the donors did not achieve the target value of 15 cells/uL of PB-CD34⁺cell at day-4, hence were subjected to apheresis at day-5 and -6.

Total apheresis days were one, two and three in 45.2%, 52.4%, and 2.4%.

78.6% of donors achieved the target goal of 510⁶ CD34⁺ cells/kg after completion of apheresis with 45.2%

of donors achieving this value after one cycle of apheresis.

Median total CD34⁺cells/kg harvested was 7.310⁶/kg and total G-CSF vials used was 10 per donor. The median CD34⁺cells yield was 2-fold higher after the first apheresis compared to the second apheresis (4.810⁶/kg vs 3.010⁶/kg) (Table 2).

3.2. Procedure-related adverse effects

Placement of central venous catheter was possible in all donors without major complications. In general, most do-

nors tolerated G-CSF therapy and apheresis. Mild paresthe- sia was observed, which was resolved with calcium sup- plement and did not require discontinuation of apheresis Thrombocytopenia of less than 10010⁹/L was observed in 16 out of 84 donors (19%). No donors had platelet counts (PC) of less than 5010⁹/L. PC normalized within 1 week after completion of apheresis in all donors.

3.3. Kinetics of leukocyte count (LC), monocyte count (MC), PC, and PB-CD34⁺cell count

The mean LC, MC and PC prior to initiation of G-CSF were within normal range in all donors (Table 2).

The mean LC count increased rapidly after G-CSF injec- tion and peaked on day-6 of G-CSF (55.1 ± 8.1). The mean MC peaked at day-4 (3.9 ± 1.0) of G-CSF and declined to normal value at day-6. The mean PC started to decrease on day-5 of G-CSF (167.5 ± 5.9, P< 0.0005) and but re- mained within normal range after completion of six days of G-CSF injection (143.3 ± 23.2, P< 0.0005). The PB- CD34⁺ cell count rapidly increased with G-CSF injection, peaking at day-4 (mean; 83.1 ± 5.9) and significantly de- creased at day-5 and day-6 of G-CSF (53.2 ± 4.3, 22.7 ± 6.3, P= 0.01; P= 0.02) (Table 2). There was asyn- chrony between the kinetics of PB-CD34⁺cell count and LC following G-CSF injection; PB-CD34⁺cell count peaked on day-4 and markedly decreased on day-6 of G-CSF, Table 1

Donor and apheresis data.

Parameters Donor (n= 84)

Age (years) 28.0 ± 1.3 26 (11–63)^a

<18 years old 22 (26.2%)

Weight (kg) 61.4 ± 1.9 60 (27–113)^a

Body mass index (kg/m²) 23.2 ± 0.63 22.8 (13.7–37.8)^a

Gender

Male 54 (64.3%)

Female 30 (35.7%)

Numbers of apheresis day

1 38 (45.2%)

2 44 (52.4%)

3 2 (2.4%)

Total vial of GCSF 9.3 ± 0.1 10 (8–14)^a

Total CD34⁺cells harvested (10⁶/kg) 7.8 ± 0.4 7.3 (0.8–17.4)^a

Number of patients

YieldP5106 CD34⁺cells/kg after completed collection 66 (78.6%) Yield < 510⁶CD34⁺cells/kg after completed collection 18 (21.4%) Number of patients

YieldP210⁶CD34⁺cells/kg after completed collection 82 (97.6%) Yield < 210⁶CD34⁺cells/kg after completed collection 2 (2.4%) Number of patients

YieldP510⁶CD34⁺cells/kg at first collection 39 (46.4%) Yield < 510⁶CD34⁺cells/kg at first collection 45 (53.6%) Number of patients

YieldP210⁶CD34⁺cells/kg at first collection 74 (88.1%) Yield < 210⁶CD34⁺cells/kg at first collection 10 (11.9%) Values are mean ± SEM.

aMedian (range).

Table 2

Kinetics of Leukocyte, Monocyte, Platelet, PB CD34⁺cells and total CD34⁺cells harvested among healthy donors.

Days of G-CSF injection D0 (n= 84) D2 (n= 39) D3 (n= 52) D4 (n= 83) D5 (n= 58) D6 (n= 5) Pvalue

Leukocyte (10⁹/L) 7.6 (4.1–13.4) 37.0 (11–60) 43.3 (16–70) 47.9 (21–100) 50.9 (22–99) 52.5 (34–90) D0 vs D360.0005^a D0 vs D460.0005^a Monocyte (10⁹/L) 0.5 (0.1–0.9) 1.2 (0.5–3.7) 1.6 (0.2–4.9) 1.7 (0.2–57.4) 1.2 (0.1–62.9) 1.1 (0.2–2.6) D0 vs D4 = 0.004^a

D3 vs D4 = 0.928^a Platelet (10⁹/L) 289 (39–409) 258 (170–354) 257.5 (171–354) 247 (145–385) 156 (69–367) 125 (72–256) D4 vs D560.0005^a

D5 vs D660.0005^a PB CD34⁺cell count (cells/lL) 7.4 (0–73.4) 35.9 (8–173.3) 73.3 (10–277) 47.2 (12–166) 18.2 (8–42) D4 vs D5 = 0.011^a

D5 vs D6 = 0.020^a

CD34⁺cells harvested (10⁶/kg) 4.8 (0.6–15.9) 3.0 (1.1–7.6) 0.9 (0–5) D4 vs D5 = 0.044^a

n= no of patients.

Values shown are median (ranges).

aPaired samplet-test.

whereas LC kept increasing from day 2 until day-6 of G-CSF. The kinetics of PB-CD34⁺cell count seemed to syn- chronize with MC as both parameters peaked at day-4 and showed a declining trend from day-5 onwards. There was no relationship observed between PB-CD34⁺ cell count and PC (Fig. 1).

3.4. Factors associated with pre-apheresis PB-CD34+ cell count

We then examined the relationship between donor demographic data and blood counts and PB-CD34⁺ cell count to determine if we can use these parameters to pre- dict the timing of apheresis. Multivariate analysis showed that pre-apheresis LC and MC were the only parameters that independently correlated with PB-CD34⁺ cell count performed on day-4 and -5 of G-CSF injection. There were

no relationship between donor’s age, weight and pre- apheresis PC with PB-CD34⁺cell count (Table 3A).

3.5. Factors associated with the yield of G-CSF-mobilized CD34+ cell

Next, we examined the donor demographic data and blood counts that can influence the CD34⁺cell yield after apheresis. In a univariate analysis, pre-apheresis LC and PB-CD34⁺cell count on day-4 and -5 of G-CSF were signif- icantly correlated with CD34⁺ cells harvested per-day (Table 3B). Multivariate analysis showed that only PB- CD34⁺cell count on day-4 (r= 0.339,P< 0.0005) and day- 5 (r= 0.384, P= 0.01) had a significant association with CD34⁺cell yield while the association between CD34⁺cell yield and pre-apheresis LC was weak for day-5 LC (r= 0.09,P= 0.04) and absent for day-4 LC. There were no relationship between donor age, BMI and weight, pre- apheresis MC and PC with CD34⁺cells harvested.

We found that a pre-apheresis LC above 44.310⁹/L plus PB-CD34⁺cell count above 36.7/

l

L after day-4 of G- CSF, and LC above 50.510⁹/L plus PB-CD34⁺cell count above 43.9/

l

L after day-5 of G-CSF, correlated with at least 2.010⁶/kg CD34⁺cells collected per-day. A pre-apheresis LC above 54.310⁹/L plus PB-CD34⁺cell count above 87.1/

l

L; and LC above 60.310⁹/L plus PB-CD34⁺ cell count above 69.8/

l

L after day-4 and -5 of G-CSF, respectively, correlated with at least 5.010⁶/kg CD34⁺cells collected per-day.

Slightly less than half (39 of 84.45.2%) of the donors achieved the target collection of 510⁶ CD34⁺ cells/kg after the first apheresis, with a median of 8.310⁶/kg CD34⁺cells harvested.

The parameters of donors who were successful in obtaining a PBSC dose of 510⁶CD34⁺cells/kg after one cycle of apheresis (Group A) were compared to those who failed to achieve this target PBSC value (Group B) (Ta- ble 4). Multivariate analysis showed that gender and PB- CD34⁺cell count were different between the two groups.

The failure rates of female donor were 2 times higher (46.7% vs 23.1%,P= 0.021), while the mean PB-CD34⁺cell count was twofold lower (51.8 ± 4.6 vs 118.4 ± 8.4, 6

5 4 3 2 1 0

Days of G-CSF treatment Leukocyte, Monocyte, platelet (x109/L) PB CD34+(cells/ul)

0 50 100 150 200 250

300 LEUKOCYTE

MONOCYTE PLATELET PB CD34+ CELLS

Fig. 1.Kinetics of leukocyte count, monocyte count, platelet count (10⁹/ L), and PB CD34⁺cell count (cells/lL) vs days of G-CSF injection.

Table 3A

Relationship between pre-apheresis PB CD34⁺cell count and donor factors at Day 4 and Day 5 of G-CSF injection.

Leukocyte Monocyte Platelet Age BMI Weight

Pre-apheresis PB CD34⁺cell count at Day 4

Pvalue 0.00 0.03 0.82 0.77 0.38 0.40

rvalue 0.41 0.33 0.03 0.03 0.10 0.09

r^2* 0.23 0.00 0.00 0.000 0.00 0.00

Pvalue^* 0.00 0.01 0.58 0.86 0.65 0.55

Day 5

Pvalue 0.00 0.02 0.33 0.84 0.91 0.29

rvalue 0.50 0.32 0.14 0.03 0.02 0.15

r^2* 0.27 0.13 0.01 0.00 0.00 0.01

Pvalue^* 0.00 0.01 0.57 0.86 0.99 0.43

All using Spearman’s Rank Order Correlation test.

*Linear regression value.

P< 0.0005) in group B compared to group A. There were no significant differences in other parameters including age, weight, BMI, LC, MC and PC between the two groups.

4. Discussion

Although PBSC are widely used in allogeneic HSCT, there has been conflicting results regarding factors that may influence the yield of PBSC mobilized with G-CSF in healthy donors. The aim of this study was to determine do- nor factors that may influence the yield of PBSC mobilized with G-CSF and to identify factors that can be used to predict poor mobilizers among healthy adult donors.

In this study we aim to harvest a minimum of 510⁶ CD34⁺cells/kg per donor from one to 3 cycles of apheresis.

In the present study, we showed that donor gender and pre-apheresis PB-CD34⁺ cells were the most important

factors that consistently influence the yield of PBSC har- vested from healthy donors.

In agreement with previous studies [12,18,25], we showed that female gender was associated with a lesser ability to harvest the target stem cell dose of at least 510⁶CD34⁺cells/kg after a single apheresis compared to male donors. In contrast, two other studies[17,22]did not find significant correlation between donor gender and yield of harvested PBSC. The true underlying reasons for the relatively poor HSC mobilization by G-CSF in female donors remain to be elucidated. However, several explana- tions have been suggested including a different interaction between G-CSF and gender[26], and the inferior circula- tion access among female donors[12].

The current study confirms the findings of previous studies [17,25,27] that showed higher circulating CD34⁺ cells count was associated with a greater PBSC yield sug- gesting that the effectiveness of collection is related to Table 3B

Relationship between total CD34⁺harvested and donor factors at Day 4 and Day 5 of G-CSF injection.

Leukocyte Monocyte Platelet PB CD34⁺ Age BMI Weight

Total CD34⁺cells harvested Day 4

Pvalue 0.02 0.28 0.06 0.00 0.41 0.28 0.15

rvalue 0.26 0.12 0.20 0.72 0.09 0.13 0.16

r^2* 0.03 0.00 0.05 0.34 0.00 0.01 0.04

Pvalue^* 0.09 0.62 0.05 0.00 0.58 0.40 0.08

Day 5

Pvalue 0.04 0.95 0.53 0.00 0.39 0.81 0.73

rvalue 0.26 0.01 0.09 0.43 0.13 0.04 -0.05

r^2* 0.09 0.00 0.00 0.38 0.00 0.01 0.00

Pvalue^* 0.04 0.86 0.90 0.01 0.68 0.61 0.95

All using Spearman’s Rank Order Correlation test.

*Linear regression value.

Table 4

The demographic and blood count profiles in donors who achieved the target dose of CD34⁺cells >510⁶/kg (group A) vs donors who achieved <510⁶CD34⁺ cells/kg (group B) after 1st cycle of apheresis.

Parameters Group An= 39 Group Bn= 45 Pvalue

Age (year) 28 (11–57) 25 (11–63) 0.332^a

0.212^c

Weight (kg) 64.8 (38–113) 60 (27–106) 0.357^a

0.389^c

BMI (kg/m²) 23.8 (15.2–37.8)^⁄ 22 (13.7–37.6)^⁄ 0.543^a

0.700^c Sex

Male 30 (76.9%) 24 (53.3%) 0.039^b

Female 9 (23.1%) 21 (46.7%) 0.021^c

Leukocyte (10⁹/L) 48.5 (36–100) 47 (21–99) 0.074^a

0.388^c

Monocyte (10⁹/L) 1.6 (0.2–57.4) 1.7 (0.2–51.4) 0.362^a

0.293^c

Platelet (10⁹/L) 230 (145–369) 257.5 (154–385) 0.101^a

0.045^c

PB CD34⁺cell count (cells/lL) 104 (37–277) 47.3 (10–137) <0.0005^a

<0.0005^c CD34⁺cells harvested after 1st apheresis (10⁶/kg) 8.3 (5.0–15.9) 3.2 (0.6–4.9) <0.0005^a

<0.0005^c Values shown are median (ranges).

aMann–Whitney U test.

bFisher exact test.

c Stepwise logistic regression.

ability to mobilize stem cells from its niche in the bone marrow. PB-CD34⁺cell count is the most reliable predictor of CD34⁺cell yield, however due to its high cost it is not routinely performed prior to apheresis. This has prompted us to search for donor’s parameters that can be used to estimate circulating CD34⁺cell count.

We found that pre-apheresis LC and MC performed on day-4 and -5 of G-CSF injection were the only parameters that independently correlated with PB-CD34⁺cell count.

Furthermore, the kinetics of PB-CD34⁺cell count and MC were well synchronized with the peaks occurring on day- 4. Therefore, LC and MC may be useful surrogate markers for estimating the numbers of circulating CD34⁺cells and in a resource limited setting may be utilized as alternative tests to determine the timing of apheresis. Donor’s age, BMI and weight and PC did not influence the pre-apheresis PB-CD34⁺ cell count. The findings in our study are sup- ported by another study that showed PB-CD34⁺cell count is associated with pre-apheresis LC but not donor’s age [13]. The question whether age has a negative impact on mobilization among PBSC healthy donors remains contro- versial[18]. Previous reports showed that donor’s age is an important factor in predicting G-CSF induced PBSC yield [17,28,29]while we and others[12,22,25]showed that age did not significantly influence PBSC yield. Suzuya et al.[17]

showed that younger age was associated with a higher PBSC yield, while de la Rubia et al.[28]reported that donor age above 38 years as a factor associated with a low PBSC yield. The difference in the observations between our study and the previous studies could be related to the difference in the age distribution among the donors. For example, the donors studied by Suzuya et al.[17]were relatively youn- ger compared to our donors; median age: 16 vs 26 years;

respectively. It has been postulated that age-associated loss of BM hematopoietic function might play a role[30].

The negative effect of increased age on PBSC mobilization is important to consider in view of the increasing use of older donors for allogeneic reduced-intensity conditioning transplant. Further study is required to confirm the effect of age on PBSC yield and if age-associated reduced or loss of stem cell mobilization in response to G-CSF treatment truly exists.

In contrast to a previous study that showed an inverse relationship between PC and PBSC yield[17], we did not observe significant association between pre-apheresis PC with PBSC yield and hence PC alone might not be useful indicator of a poor mobilizer among healthy donors. We did not observe any correlation between donors’ weight or BMI and PBSC yield. This is in contrast to previous stud- ies[17,23,31]that showed donors with a lower BMI had a lower CD34⁺cells yield.

Next, we attempted to determine if we can identify do- nors that were able to achieve the target dose of PBSC after a single apheresis. Approximately less than half of our do- nors achieved the target PBSC dose of 510⁶CD34⁺cells/

kg after the first apheresis. This observation is in agree- ment with IBMTR/EBMT data that 60% of donors required more than one apheresis to collect at least 510⁶CD34⁺ cells/kg [32]. Gender and PB-CD34⁺cell count appeared to influence the target PBSC dose obtained in our study.

The failure rate of female donors to achieve the target PBSC

dose was 2–3 times more, while the mean PB-CD34⁺cell count was twofold lower among donors who failed to achieve the target PBSC dose after a single apheresis.

We showed that a pre-apheresis LC above 54.310⁹/L and PB-CD34⁺cell count above 87.1/

l

L after day-4 of G- CSF; and LC above 60.310⁹/L and PB-CD34⁺cell count above 69.8/

l

L after day-5 of G-CSF, correlated with at least 5.010⁶ CD34⁺ cells/kg harvested per apheresis. These cut-off values might be helpful in ascertaining if a donor would require more than a single apheresis to meet the target dose of PBCS required for HSCT.

5. Conclusion

In conclusion, our data suggest that pre-apheresis PB- CD34⁺cell count and gender are the only factors that con- sistently influence G-CSF mobilized PBSC yield in healthy adult donors. Other donor factors including age, BMI and pre-apheresis full blood counts had little impact with PBSC yield. Future studies should investigate if these parameters can be incorporated into a mathematical model that may be used to determine the timing of apheresis to achieve optimal PBSC yield and to predict the outcome of G-CSF mobilization among healthy donors. In donors at high risk of mobilization failure, new mobilization strategies may be considered in order to increase the yield and to minimize the exposure to G-CSF injections and reduce the number of apheresis. The underlying mechanisms by which the do- nor factors affecting the yield of mobilized PBSC merit fur- ther investigation.

Acknowledgments

We thank the doctors and nurses involved in the care of the donors and the Dean of the Faculty for supporting the study. All authors approved the submitted version.

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The author has requested enhancement of the downloaded file. All in-text references underlined in blue are linked to publications on ResearchGate.

The author has requested enhancement of the downloaded file. All in-text references underlined in blue are linked to publications on ResearchGate.