Multiple-laboratory comparison of in vitro assays utilized to characterize hematopoietic cells in cord blood.
BACKGROUND
Understanding the variability in results obtained by multiple laboratories is important because cord blood units are distributed worldwide for transplantation.


METHODS
Four exercises were conducted by multiple laboratories to assess assay variability on nucleated cell (NC), mononuclear cell (MNC) by hematology analyzers [HAs], and CD34+ cell (flow cytometry) measurements. Exercise 1 was an intralaboratory exercise in which the reproducibility of cell measurements was determined. Exercises 2 and 3 involved the shipment of identical processed cord blood samples. In Exercise 2, laboratory-specific methods were utilized. In Exercise 3, two commercial CD34+ cell methods (Stem-Kit and TruCOUNT) were used. In Exercise 4, CD34+ cell levels were determined on repetitive regating of identical list-mode files.


RESULTS
Intralaboratory reproducibility was highest for NC measurements and lowest for CD34+ cell measurements. In Exercise 2, all laboratories except one utilized HA with an impedance technology and determined comparable results for NC and MNC levels, whereas the other laboratory utilized a HA with an optical counting method. Substantial variation was observed on measuring CD34+ cells with ranges of 32 to 141, 32 to 66, and 25 to 116 CD34+ cells per microL for the three identical samples. In Exercise 3, on the use of one specific commercial assay, the ranges of CD34+ levels were 214 to 411 and 62 to 178 cells per microL for the two identical samples. Nearly all participating laboratories determined comparable CD34+ levels on the use of identical list-mode files.


CONCLUSIONS
These studies indicate that substantial variability in CD34+ cell levels were determined with flow cytometry. The variability in NC and MNC levels was minimal with HA methodology.
American Red Cross, Jerome H. Holland Laboratory for the Biomedical Sciences, Rockville, MD 20855, USA. moroff@usa.redcross.org
Gary
G
Moroff
Hermann
H
Eichler
Anneke
A
Brand
Riitta
R
Kekomäki
James
J
Kurtz
Magdalena
M
Letowska
Derwood
D
Pamphilon
Elizabeth J
EJ
Read
Laura
L
Porretti
Lucilla
L
Lecchi
Jo-Anna
JA
Reems
Ronald
R
Sacher
Shalini
S
Seetharaman
Tsuneo A
TA
Takahashi
D015703:Antigens, CD / Q000097:blood; D018952:Antigens, CD34 / Q000097:blood; D005312:Fetal Blood / Q000166:cytology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D007753:Laboratories / Q000592:standards*; D015203:Reproducibility of Results
D015703:Antigens, CD; D018952:Antigens, CD34