Performance Characteristics of the Coulter LH 500 Hematology Analyzer

The challenge for modern hematology laboratories is to provide accurate and reproducible results, with seamless performance between facilities, in a cost-effective manner. Beckman Coulter recently developed the Coulter LH 500 to meet the needs of smaller laboratories or serve as a backup in larger laboratories. The principal goal of this study was to validate all parameters and performance specifications of the LH 500 compared to the Coulter LH 750 predicate analyzer. A total of 245 spent clinical samples from the London Health Sciences Centre (LHSC) and 251 from the University of Pittsburgh Medical Center Health System (UPMCHS) were analyzed during the study. The samples were selected to include 75% abnormal and 25% normal blood samples. According to the results of a rank sum test, there was no significant difference between the LH 500 and LH 750 for all complete blood count parameters (P > .05) except the red cell distribution width, which showed a slight negative bias on the LH 500. Differential parameters comparing the LH 500 to a 400-cell manual differential showed correlation coefficients (r2) from 0.75 to 0.99 for all parameters except basophils. Of the samples run on the LH 500 at LHSC, the false-positive differential flagging rate was 17.32% and the false-negative rate was 3.03%. Sensitivity was 82.93%, specificity 78.95%, and efficiency 79.65%. At UPMCHS, the false-positive differential flagging rate was 13.37% and false-negative rate 2.97%. Sensitivity was 91.89%, specificity 78.91%, and efficiency 83.66%. Overall, the LH 500 performed accurately and reproducibly compared to the LH 750 and the reference procedures. It would be an excellent second instrument for larger laboratories concerned with harmonization of instrumentation and reagents or as a primary instrument for smaller hematology laboratories with limited space.

Impact of standardization on clinical cell analysis by flow cytometry

The evolution of flow cytometry from a research tool to a pivotal technology for clinical diagnostic purposes has required significant efforts to standardize methods. The great advantage of flow cytometry is that it's applications are highly amenable to standardization. Here, we review the efforts that have been made for flow cytometric applications in four major fields of clinical cell analysis: CD4+ T-cell enumeration, CD34+ hematopoietic stem and progenitor cell enumeration, screening for the HLA-B27 antigen and leukemia/lymphoma immunophenotyping. These standardization efforts have been parallelled by the establishment of external quality assessment (EQA) schemes in many countries worldwide. The goal of these EQA exercises has been primarily educa-tional, but their results will increasingly serve as a basis for laboratory accreditation. This important development requires that the EQA schemes, in particular the quality of the distributed samples and the procedures for evaluating the results, meet the highest standards.

Validation of the single-platform ISHAGE method for CD34(+) hematopoietic stem and progenitor cell enumeration in an international multicenter study

BACKGROUND

Flow cytometric enumeration of CD34+ hematopoietic sterm and progenitor cells (HPC) is the reference point for undertaking apheresis and evaluation of adequacy for PBSC engraftment. An external quality assurance (EQA) scheme for CD34+ HPC enumeration has been operational in Belgium, Netherlands and Luxemburg (Benelux) since 1995. Within this group, a multicenter survey was held to validate the state-of-the-art methodology, i.e., multiparametric definition of HPC based on light scatter, expression of CD34 and CD45, and counting beads (i.e., 'single platform ISHAGE' method).

METHODS

'Real-time' EQA was used to monitor the application of the single-platform ISHAGE method by 36 participants. Three send-outs of stabilized blood with CD34+ cell counts 35-60 cells/microl were distributed to 36 participants, who were required to assay the samples on three occasions using the standard assay and their local techniques. These results were compared with thosed obtained by 111-116 UK NEQAS participants testing the same specimens.

RESULTS

Using the single platform ISHAGE methods, between-laboratory coefficients of variations (CVs) as low as 10% were achieved. Intra-laboratory CVs were < 5% for approximately 50% of the participants. Local single-platform techniques yielded between-laboratory CVs as low as 9% in both Benelux and UK NEQAS cohorts. In contrast, the lowest between-laboratory CVs using dual-platform techniques were 17% (Benelux) and 21% (UK NEQAS), respectively.

CONCLUSION

The single-platform ISHAGE method for CD34+ cell enumeration has been validated by an international group of 36 laboratories. The observed varation between laboratories allows a meaningful comparison of CD34+ cell enumeration.

Effect of 3.2 vs. 3.8% sodium citrate concentration on anti-Xa levels for patients on therapeutic low molecular weight heparin

In this study, we compared the effect of sodium citrate, a sample collection variable, on the anti-Xa levels of patients (n = 28) on dalteparin, a low molecular weight heparin. The median anti-Xa level for 3.2% sodium citrate was 0.235 U/ml while the median level for 3.8% sodium citrate was 0.230 U/ml. We conclude that different sodium citrate concentrations give statistically equivalent anti-Xa levels for the same samples. This conclusion is in contrast to the findings of the effect of sodium citrate concentration on International Normalized Ratio (INR) and activated partial-thromboplastin time (aPTT). In accordance with previous recommendations, we advocate the exclusive use of 3.2% sodium citrate in an effort to standardize coagulation testing.

Prospective assessment of the natural history of positive D-dimer results in persons with acute venous thromboembolism (DVT or PE)

The natural history of initially positive D-dimers for venous thromboembolism is not known. If it returns to negative in the majority of patients, it would be potentially helpful to diagnose a recurrence. In this study, we prospectively measured D-dimer levels in outpatients with a diagnosis of venous thromboembolism. There were a total of 152 patients with an average age of 57. D-dimer results were performed at baseline and repeated at one week, one month and three months. At baseline 120 of 152 (79%) had a positive D-dimer result. Of those with an initially positive result, 80% were still positive at one week and 39% were still positive at one month. Finally at three months, 13% remained positive. Seven patients had recurrent events and all had persistently elevated D-dimers at one month. This study suggests that a persistently positive D-dimer result after one month of treatment may indicate a higher risk of recurrent venous thromboembolism. D-dimer testing for the diagnosis of recurrence of venous thromboembolism deserves further study.

Validation of body fluid analysis on the Coulter LH 750

The role of the hematology laboratory in the analysis of body fluid has been to provide accurate enumeration of red blood cells (RBCs), total nucleated cells (TNCs), and differentials by manual analysis. Three hospitals (London Health Sciences Centre, University of Pittsburgh Medical Center, and University of Michigan Health System) participated in the assessment of the performance of automated analysis of body fluid by the Beckman Coulter LH 750, an impedance-based hematology analyzer. We evaluated the accuracy of analysis results for both the TNCs and RBCs of 372 samples (158 serous fluid, 148 cerebrospinal fluid [CSF], 66 synovial fluid) run on the LH 750 compared to results obtained from manual chamber counting. Of the 372 samples, 152 were suitable for evaluation of accuracy of the automated TNC. The remaining 220 samples were either flagged for interfering substances or the reference results were < 0.2 x 10(9)/L, below the background limit of the analyzer. Correlation coefficients for serous fluid were 0.895, P = .88; for CSF, 0.993, P = .84; and for synovial fluid, 0.836, P = .94. Of the 372 samples, 106 had RBC counts greater than 0.01 x 10(12)/L and were used for method comparison. Correlation coefficients for serous fluid were 0.957, P = .66; for CSF, 0.849, P = .55; and for synovial fluid, 0.667, P = .81. Linearity and precision studies showed excellent agreement for both TNC and RBC parameters. Low-level sensitivity excluded the majority of cerebrospinal (119) and a small number of peritoneal dialysate fluid samples (8), which require accurate enumeration at clinical decision points between 0 to 100 cells/microliter. In the case of synovial and serous fluids, however, most clinicians are interested in TNC counts above 0.2 x 10(9)/L, and RBC counts are relevant only if they are significantly increased (> or = 0.05 x 10(12)/L). Adopting the criteria of reporting TNC counts as < 0.2 x 10(9)/L or accurate enumeration on counts > or = 0.2 x 10(9)/L, clinically relevant results could be provided by automated analysis in 93.8% of serous fluids and 85.8% of synovial fluids.

Optimising parameters for peripheral blood leukapheresis after r-metHuG-CSF (filgrastim) and r-metHuSCF (ancestim) in patients with multiple myeloma: a temporal analysis of CD34(+) absolute counts and subsets

Patients (n = 69) with multiple myeloma undergoing peripheral blood stem cell collection (PBSC) were treated with cyclophosphamide and a combination of recombinant methionyl human granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim) and recombinant methionyl human stem cell factor (r-metHuSCF, ancestim). The objectives of this study were to determine: (1) The proportion of patients reaching a target yield of >or=5 x 10(6) CD34(+) cells/kg in one or two successive large-volume (20 liter) leukapheresis procedures; (2) the optimal collection time for leukapheresis; (3) mobilization kinetics of CD34(+) subsets in response to G-CSF/SCF. All patients were mobilized with cyclophosphamide (2.5 g/m(2)) on day 0 followed by filgrastim (10 microg/kg ) plus ancestim (20 microg/kg) commencing day 1 and continuing to day 11 or 12. Of the 65 evaluable patients, 57 were considered not heavily pretreated and 96.5% obtained a target of >or=5 x 10(6)/kg in one collection. The median CD34(+) cells/kg was 39.5 x 10(6) (range: 5.2-221.2 x 10(6)). Subset analysis demonstrated the number of CD38(-), CD33(-), and CD133(+) peaked at day 11; and CD34(+), CD90(+) cells peaked at day 10. The optimum day for leukapheresis was determined to be day 11. The median absolute peripheral blood CD34(+) cell numbers on day 11 was 665 x 10(6)/l (range: 76-1481 x 10(6)/l). Eight of the 10 heavily pretreated patients were evaluable: three achieved the target dose in one leukapheresis (37.5%) and three (37.5%) achieved the target dose with two leukaphereses. Use of this mobilization strategy allowed the collection of high numbers of CD34(+) cells and early progenitors and the ability to predictably schedule leukapheresis.

Functional analysis of human hematopoietic repopulating cells mobilized with granulocyte colony-stimulating factor alone versus granulocyte colony-stimulating factor in combination with stem cell factor

Using in vitro progenitor assays, serum-free in vitro cultures, and the nonobese diabetic/severe combined immune-deficient (NOD/SCID) ecotropic murine virus knockout xenotransplantation model to detect human SCID repopulating cells (SRCs) with multilineage reconstituting function, we have characterized and compared purified subpopulations harvested from the peripheral blood (PB) of patients receiving granulocyte colony-stimulating factor (G-CSF) alone or in combination with stem cell factor (SCF). Mobilized G-CSF plus SCF PB showed a 2-fold increase in total mononuclear cell content and a 5-fold increase in CD34-expressing cells depleted for lineage-marker expression (CD34(+)Lin(-)) as compared with patients treated with G-CSF alone. Functionally, G-CSF plus SCF-mobilized CD34(+)CD38(-)Lin(-) cells contained a 2-fold enhancement in progenitor frequency as compared with G-CSF-mobilized subsets. Despite enhanced cellularity and progenitor capacity, G-CSF plus SCF mobilization did not increase the frequency of SRCs as determined by limiting dilution analysis by means of unfractionated PB cells. Purification of SRCs from these sources demonstrated that as few as 1000 CD34(+)CD38(-)Lin(-) cells from G-CSF-mobilized PB contained SRC capacity while G-CSF plus SCF-mobilized CD34(+)CD38(-)Lin(-) cells failed to repopulate at doses up to 500 000 cells. In addition, primitive CD34(-)CD38(-)AC133(+)Lin(-) cells derived from G-CSF plus SCF-mobilized PB were capable of differentiation into CD34-expressing cells, while the identical subfractions from G-CSF PB were unable to produce CD34(+) cells in serum-free cultures. Our study defines qualitative and quantitative distinctions among subsets of primitive cells mobilized by means of G-CSF plus SCF versus G-CSF alone, and therefore has implications for the utility of purified repopulating cells from these sources.

Number of viable CD34(+) cells reinfused predicts engraftment in autologous hematopoietic stem cell transplantation

Reduced CD34(+) cell viability due to cryopreservation has unknown effects on subsequent hematopoietic engraftment in autologous transplantation. Thirty-six consecutive autologous peripheral stem cell collections were analyzed for absolute viable CD34(+) cell numbers at the time of stem cell collection and prior to re-infusion. Viable CD34(+) cells were enumerated using single platform flow cytometry and the molecular exclusion dye 7-amino actinomycin D. The median number of viable CD34(+) cells was 3.6 x 10(6)/kg at the time of harvest and 2.0 x 10(6)/kg after thawing. When viable CD34(+)cells enumerated after thawing were <2.0, 2.0-5.0, or >5.0 x 10(6)/kg, the median time to platelet engraftment was 17, 12 and 10 days, respectively (P < 0.05 for comparison of the group with <2.0 x 10(6)/kg and the other two groups), and the median time to neutrophil engraftment was 13, 14 and 12 days, respectively (P = NS). A minimum of 2.0 x 10(6) CD34(+) cells/kg was harvested in 33 of 36 patients (92%) but only 19 of 36 (52%) patients met this threshold at the time of reinfusion. The reduced numbers of viable CD34(+) cells measured prior to re-infusion is associated with time to platelet engraftment and may be useful in monitoring stem cell loss during processing and identifying patients at risk of graft failure.

Comparison of five platforms for enumeration of residual leucocytes in leucoreduced blood components

The need for quality control of leucoreduction of blood products has led to the development of various methods to count low levels of residual leucocytes. We compared five platforms side-by-side: the Nageotte haemocytometer and four based on fluorescent staining of nuclei: two flowcytometers (Beckman Coulter, BD Biosciences) with methods based on counting beads, a volumetric flow cytometer (Partec) and the microvolumic fluorimeter ImagN2000 (BD Biosciences), all according to their manufacturers' recommended methods. Analysis of double-filtered red cell concentrates (RCCs) and platelet concentrates (PCs), spiked with various numbers of leucocytes, revealed good linearity for all methods over the range of 1.6-32.7 leucocytes/microl, all with r(2) > 0.99. At the rejection level of leucocyte-reduced blood components, i.e. 1 x 10(6) per unit corresponding with approximately 3.3 leucocytes/microl, the Nageotte haemocytometer had low accuracy (0% for RCCs, 56% for PCs), and was relatively imprecise [coefficient of variance (CV) of 34% and 30% respectively]. The Partec flow cytometer gave good results for RCCs (accuracy 67%, CV 22%), but not for PCs (accuracy 0%, CV 25%). The ImagN2000 had an accuracy of 44% for RCCs and 89% for PCs, but the precision was variable (CV 32% for RCCs, 15% for PCs). The best results were obtained with the Beckman Coulter (RCCs: accuracy 86%, CV 13%, PCs: accuracy 67%, CV 16%), and BD Biosciences platforms (RCCs: accuracy 100%, CV 10%; PCs: accuracy 89%, CV 11%). We conclude that, at the rejection level of 1 x 10(6) leucocytes per unit, the widely used Nageotte haemocytometer performs poorly in terms of inaccuracy and imprecision, and that both counting-bead-based, flow cytometric methods performed best.

A comparison of three rapid D-dimer methods for the diagnosis of venous thromboembolism

We compared three rapid D-dimer methods for the diagnosis of venous thromboembolism. Patients presenting to four teaching hospitals with the possible diagnosis of deep vein thrombosis or pulmonary embolism were investigated with a combination of clinical likelihood, D-dimer (SimpliRED) and initial non-invasive testing. Patients were assigned as being positive or negative for deep vein thrombosis or pulmonary embolism based on their three-month outcome and initial test results. The three D-dimer methods compared were: (a) Accuclot D-dimer (b) IL-Test D-dimer (c) SimpliRED D-dimer. Of 993 patients, 141 had objectively confirmed deep vein thrombosis or pulmonary embolism. The sensitivity of SimpliRED, Accuclot and IL-Test were 79, 90 and 87% respectively. All three D-dimer tests gave similar negative predictive values. The SimpliRED D-dimer was found to be less sensitive than the Accuclot or IL-Test. When combined with pre-test probability all three methods are probably acceptable for use in the diagnosis of venous thromboembolism.

Inactivation of p53 sensitizes U87MG glioma cells to 1,3-bis(2-chloroethyl)-1-nitrosourea

We examined the effect of p53 inactivation on the response of U87MG glioma cells to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). These studies were motivated by three observations: (a) some human astrocytomas are sensitive to BCNU and some are resistant; (b) chemosensitive astrocytomas are more likely to be found in young adults whose tumors are more likely to harbor a p53 mutation; and (c) mouse astrocytes lacking the p53 gene are more sensitive to BCNU than wild-type cells. Here, we observed that p53 inactivation by transfection with pCMV-E6 sensitized U87MG cells to BCNU. Compared with control U87MG-neo cells with intact p53 function, the clonogenic survival of U87MG-E6 cells exposed to BCNU was reduced significantly. In U87MG-E6 cells, sensitization to BCNU was associated with failure of p21(WAF1) induction, transient cell cycle arrest in S phase, accumulation of polyploid cells, and significant cell death. In contrast, resistance to BCNU in U87MG-neo cells was associated with up-regulation of p53, prolonged induction of p21(WAF1), sustained cell cycle arrest in S phase, and enhancement of DNA repair. U87MG cells with disrupted p53 function were less able to repair BCNU-induced DNA damage and survive this chemotherapeutic insult. The question arises of whether p53 dysfunction might be a chemosensitizing genetic alteration in human astrocytic gliomas.

Flow cytometric enumeration and immunophenotyping of hematopoietic stem and progenitor cells

Flow cytometric enumeration of CD34(+) hematopoietic stem and progenitor cells (HPC) is widely used to evaluate the adequacy of peripheral blood stem cell grafts and is also useful for planning the apheresis sessions needed to obtain these grafts. A state-of-the-art method to enumerate CD34(+) cells has been developed that makes use of a multiparameter definition of HPC, based on their light scatter characteristics and dim expression of CD45, utilizing fluorescent counting beads. This approach allows the absolute CD34(+) cell count to be determined directly from a flow cytometer. The method can be extended with a viability stain and additional markers for further immunologic characterization of CD34(+) cells, and has been successfully implemented in multicenter trials. Using such a standardized assay, it should be possible to define more accurately the lower threshold for a safe HPC graft in terms of short- and long-term hematopoietic reconstitution. Semin Hematol 38:139-147.