P3397Risk Or Benefit IN Screening for CArdiovascular disease (ROBINSCA): results from screening for a high cardiovascular disease risk by using a risk prediction model or coronary artery calcium scoring

Introduction

The ROBINSCA (Risk Or Benefit IN Screening for CArdiovascular disease) trial is a large-scale population-based randomized controlled screening trial with the aim to investigate whether screening for a high risk of cardiovascular disease (CVD) by means of either the Systematic COronary Risk Evaluation (SCORE) model or coronary artery calcium (CAC) scoring followed by preventive treatment is effective in reducing morbidity and mortality from coronary heart disease (CHD). This study shows the results of the CVD risks as assessed by the two screening tools.

Methods

Based on the Dutch population registry, 394,058 men aged 45–74 years and women aged 55–74 years received an information brochure, an invitation to participate in the trial, a baseline questionnaire with waist circumference tape and an informed consent form. Eligible individuals with an expected high CVD risk were randomized (1:1:1) into a control arm (n=14,519), intervention arm A (n=14,478) or intervention arm B (n=14,450). In the control arm, usual care was continued. In intervention arm A, participants were screened for a high risk of CVD using the SCORE model based on traditional risk factors. In intervention arm B, CAC scoring after computed tomography scanning was used for screening. After screening en risk communication, preventive treatment according to the Dutch guidelines is advised for high risk persons.

Results

Screening uptake was 84.2% in intervention arm A and 89.6% in intervention arm B. Of the screened participants, 48.7% was female, median age at screening was 62 (Interquartile Range 10), 35.2% was high educated, 19.6% was baseline smoker and 41.4% had a positive family history of myocardial infarction. The assessed CVD risk status according to SCORE screening was stratified into three risk categories; 45.1% was at low risk (SCORE<10%), 26.5% was at intermediate risk (SCORE 10–20%), and 28.4% was at high risk (SCORE ≥20%). According to CAC screening, 76.0% was at low risk (Agatston <100), 15.1% was at high risk (Agatston 100–399), and 8.9% was at very high risk (Agatston ≥400). Associations between baseline variables and increased CVD risk will be analyzed soon and will be available in summer 2019.

Conclusions

Using different screening tools resulted in reclassification of the CVD risk. CAC screening caused a substantial shift to more low risk individuals. This might, when screening is found to be effective, lead to less overtreatment in prevention of CVD events. Future 5-year follow-up data should provide evidence about whether population-based screening with subsequent preventive treatment is (cost-)effective in reducing CHD-related morbidity and mortality.

Prognostic value of circulating tumour cells for early recurrence after resection of colorectal liver metastases

BACKGROUND

Despite good outcomes for many, a substantial group of patients undergoing metastasectomy for isolated liver metastases from colorectal cancer (CRC) experience early recurrence. We have investigated whether circulating tumour cell (CTC) detection can identify patients developing disease recurrence within 1 year after liver metastasectomy.

METHODS

In CRC patients undergoing liver metastasectomy, 30 ml peripheral blood was withdrawn preoperatively. CTCs were detected by the CellSearch system after a density-gradient-based enrichment step.

RESULTS

One hundred and seventy-three samples from 151 individual patients were analysed. In 75 samples (43%), CTCs were detected, 16% had ⩾3 CTCs/7.5 ml of blood. Eighty-two patients (47%) experienced early disease recurrence (<1 year). The 1-year recurrence rate between patients with or without detectable CTCs were similar (47% vs 48%) or with a low or high CTC count (<3 or ⩾3 CTCs/7.5 ml of blood) (50% vs 47%). Also disease-free and overall survival were similar between patients with or without CTCs.

CONCLUSIONS

The presence of CTCs in preoperative peripheral blood samples does not identify patients at risk for early disease recurrence after curative resection of colorectal liver metastases. Other parameters are needed to better identify patients at high risk to relapse after liver metastasectomy for CRC.

Tumor heterogeneity makes AML a "moving target" for detection of residual disease

Detection of minimal residual disease is recognized as an important post-therapy risk factor in acute myeloid leukemia patients. Two most commonly used methods for residual disease monitoring are real-time quantitative polymerase chain reaction and multiparameter flow cytometry. The results so far are very promising, whereby it is likely that minimal residual disease results will enable to guide future post-remission treatment strategies. However, the leukemic clone may change between diagnosis and relapse due to the instability of the tumor cells. This instability may already be evident at diagnosis if different subpopulations of tumor cells coexist. Such tumor heterogeneity, which may be reflected by immunophenotypic, molecular, and/or cytogenetic changes, can have important consequences for minimal residual disease detection, since false-negative results can be expected to be the result of losses of aberrancies used as minimal residual disease markers. In this review the role of such changes in minimal residual disease monitoring is explored. Furthermore, possible causes of tumor instability are discussed, whereby the concept of clonal selection and expansion of a chemotherapy-resistant subpopulation is highlighted. Accordingly, detailed knowledge of the process of clonal evolution is required to improve both minimal residual disease risk stratification and patient outcome.

Tumor heterogeneity makes AML a "moving target" for detection of residual disease

Detection of minimal residual disease is recognized as an important post-therapy risk factor in acute myeloid leukemia patients. Two most commonly used methods for residual disease monitoring are real time quantitative polymerase chain reaction and multiparameter flow cytometry. Results so far are very promising, whereby it is likely that minimal residual disease results will enable to guide future post-remission treatment strategies. However, the leukemic clone may change between diagnosis and relapse due to instability of the tumor cells. This instability may already be evident at diagnosis if different subpopulations of tumor cells coexist. Such tumor heterogeneity, which may be reflected by immunophenotypic, molecular and/or cytogenetic changes, can have important consequences for minimal residual disease detection, since false-negative results can be expected to be the result of losses of aberrancies used as minimal residual disease markers. In this review the role of such changes in minimal residual disease monitoring is explored. Furthermore, possible causes of tumor instability are discussed, whereby the concept of clonal selection and expansion of a chemotherapy resistant subpopulation is highlighted. Accordingly, detailed knowledge of the process of clonal evolution is required to improve both minimal residual disease risk stratification and patient outcome. © 2013 Clinical Cytometry Society.

A new approach for rapid and reliable enumeration of circulating endothelial cells in patients

BACKGROUND

Mature circulating endothelial cells (CECs) are surrogate markers of endothelial damage/dysfunction. A lack of standardized assays and consensus on CEC phenotype has resulted in a wide variation of reported CEC numbers (4-1300 per mL).

OBJECTIVES

Given the need for a quick, reliable, robust and validated CEC assay at an affordable price, we present a novel approach to enumerate CECs using a multi-parameter flow cytometric (FCM) method without immunological pre-enrichment.

METHODS

CECs were defined as CD34+, CD45neg, CD146+ and DNA+ events based on the immunophenotype of endothelial cells from vein-wall dissections. As CECs express high levels of CD34, we based our assay on absolute CD34 counts after analyzing all CD34 positive events in a total blood volume of 4 mL needed for a precise enumeration of CECs at a frequency of < 1 cell μL(-1).

RESULTS

The endothelial origin of CECs was confirmed by morphology, immunohistochemistry and gene expression. The new FCM assay was tested in parallel with a validated assay (i.e. CellSearch). CEC levels ranged from 4 to 79 CEC mL(-1) in healthy individuals and were significantly higher in patients with advanced solid malignancies (P = 0.0008) and in patients with hematological malignancies (P < 0.0001).

CONCLUSIONS

This flow cytometric method should be useful as a fast and economical assay to enumerate and characterize CECs.

Abstract P3-02-05: Evaluation of Gene Transcripts in Primary Tumors at Time of Diagnosis and Circulating Tumor Cells (CTCs) at Time of Metastatic Disease

Introduction: The enumeration of CTCs has already shown to bear clinical relevance as a prognostic and predictive factor in metastatic breast cancer. In addition to enumeration, isolation of CTCs enables their molecular characterization and thus holds great promise to establish association of their genetic profile with patient outcome and to identify potential drugable targets. In this study we established epithelial-specific mRNA and microRNA profiles in CTCs of patients with metastatic breast cancer, compared these profiles to the profiles measured in corresponding primary tumors, and determined their association with clinical parameters.

Study design:

For this study we included 50 breast cancer patients, of which 32 presented themselves with over 5 CTCs at the time of metastatic disease. From 14 of these patients with more than 5 CTCs at the time of metastatic disease also the primary tumor at time of breast cancer diagnosis was evaluated. Total RNA was extracted 1) from blood of the 50 patients with metastatic disease after EpCAM-based enrichment of 7.5 mL whole blood with the CellSearch™ Profile Kit [Veridex LCC], 2) from 14 unprocessed whole blood preparations from healthy blood donors, and 3) from 14 primary tumors. Gene transcript levels of CTC-specific and potentially clinically relevant mRNAs and microRNAs were compared in CTCs isolated at time of metastatic disease and the corresponding primary tumors. In addition, the association of these transcript levels with clinical data was assessed.

Results:

We identified 24 mRNA and 14 microRNAs more abundantly expressed in CellSearch-enriched fractions from patients with at least 5 CTCs compared with those without CTCs and/or compared with unprocessed whole blood prior to CellSearch enrichment (Mann-Whitney U-test P&lt;0.05). In addition, when comparing transcript levels present in CTCs during metastatic disease and those measured in the corresponding primary tumor, potentially clinically relevant discrepancies were observed. Findings of interest included changes in transcript levels of genes such as ESR1, ERBB2, TOP2A and MGB1, and in genes associated with proliferation and EMT. Finally, associations were observed between transcript levels measured in CTC preparations and clinical data like nodal status and size of the primary tumor.

Conclusion:

Our results show that molecular characterization of CTCs is feasible and has potential for a more tailored clinical approach above CTC enumeration in the treatment of metastatic breast cancer patients.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-02-05.

Human chorionic gonadotropin treatment of anti-Hu-associated paraneoplastic neurological syndromes

OBJECTIVE

Paraneoplastic neurological syndromes associated with anti-Hu antibodies (Hu-PNS) are mediated by a T-cell immune response that is directed against the Hu antigens. In pregnancy, many Th1-mediated autoimmune diseases such as rheumatoid arthritis and multiple sclerosis regress. We hypothesised that this decreased disease activity during pregnancy may be related to high human chorionic gonadotropin (hCG) levels.

METHODS

15 Hu-PNS patients were treated in a prospective, uncontrolled and unblinded trial with 10,000 IU daily of hCG administered by intramuscular injection during 12 weeks. Primary outcome measures were functional improvement defined as a decrease of one or more points on the modified Rankin Scale (mRS) or stabilisation in patients with mRS score ≤3 and improvement of neurological impairment assessed with the Edinburgh Functional Impairment Tests (EFIT). Secondary end points included the change in activities of daily living as evaluated using the Barthel Index.

RESULTS

Seven of 15 patients (47%) improved on the mRS or stabilised at mRS score ≤3. Four patients (27%) showed significant improvement of neurological impairment as indicated by an overall Edinburgh Functional Impairment Tests score of ≥1 point. Five patients improved on the Barthel Index (33%).

CONCLUSION

Comparison with previous studies suggests that hCG may have immunomodulatory activity and may modify the course of Hu-PNS, although well-established confounding factors may have contributed in this uncontrolled trial.

Circulating endothelial cells, circulating tumour cells, tissue factor, endothelin-1 and overall survival in prostate cancer patients treated with docetaxel

PURPOSE

We investigated whether serum markers of angiogenesis endothelin-1 (ET-1) and tissue factor (TF), and/or markers of vascular damage such as circulating endothelial cells (CECs), or their relative changes during treatment, were prognostic for overall survival (OS) in castration resistant prostate cancer (CRPC) patients. Additionally, we combined these markers with circulating tumour cells (CTCs) to construct a predictive nomogram for treatment outcome.

PATIENTS AND METHODS

One hundred and sixty two CRPC patients treated with a docetaxel containing regimen had blood drawn before and at 2-5 weeks and 6-8 weeks after treatment start. Prospectively determined CTC and CEC levels, and retrospectively measured serum concentrations of ET-1 (pg/mL) and TF (pg/mL) were evaluated to determine their prognostic value for OS.

RESULTS

Baseline CEC, TF and ET-1 were not prognostic for OS. A > or = 3.8-fold increase in CEC 2-5 weeks after treatment initiation was associated with decreased OS (median 10.9 versus 16.8 months; P=0.015), as was any decrease in TF levels compared to baseline levels (median 11.9 versus 21.5 months; P=0.0005). As previously published, baseline and CTC counts > or = 5 at 2-5 weeks were also predictive of decreased OS. Combining CTC with changes in TF and CEC 2-5 weeks after treatment initiation yielded four groups differing in OS (median OS 24.2 versus 16.0 versus 11.4 versus 6.1 months; P<0.0001).

CONCLUSION

CEC, CTC and TF levels alone and combined can predict early on OS in CRPC patients treated with docetaxel-based therapy. A prospective study to confirm the use of these markers for patient management is needed.

Retronectin-assisted retroviral transduction of primary human T lymphocytes under good manufacturing practice conditions: tissue culture bag critically determines cell yield

BACKGROUND

For our clinical immunogene therapy study for the treatment of renal cell carcinoma (RCC) patients, we had developed a protocol for gene transduction and expansion of human T cells in compliance with good manufacturing practice (GMP) criteria. Critical to our successful clinical-scale transductions of patient T cells was the use of Retronectin in combination with Lifecell X-foldtrade mark cell culture bags.

METHODS

In our current study, we evaluated two alternative types of bags for the Retronectin-mediated retroviral transduction of human T cells: the Miltenyi DC-generation bag and the Takara CultiLife Spin bag.

RESULTS

In static transductions, but not in spinoculation, the DC-generation bags and CultiLife Spin bags performed as well as Lifecell X-foldtrade mark bags in Retronectin-assisted retroviral transduction of human T cells with respect to transduction efficiency, lymphocyte subset composition and lymphocyte function. However, both types of bags performed less well than Lifecell X-foldtrade mark cell culture bags in terms of cell yield.

DISCUSSION

Adjusted numbers of cells at the start of transduction should be used when using the Miltenyi or Takara bags in order to compensate for the lower cell yield following transduction.

Bone-marrow transplantation fails to halt intrathecal lymphocyte activation in multiple sclerosis

BACKGROUND

Given the presumed key role for autoreactive lymphocytes in multiple sclerosis (MS), treatment strategies have been developed to ablate lymphocyte activity. Intrathecal lymphocyte activation can be measured by CSF-soluble(s)CD27.

OBJECTIVE

To determine the effect of maximum whole-body immune ablation on two different markers that detect lymphocyte activation in CSF-oligoclonal IgG bands and levels of CSF-sCD27.

DESIGN, SETTING AND PATIENTS

The study quantified sCD27 levels and assessed the presence of oligoclonal IgG bands in CSF samples of secondary progressive patients with MS treated by autologous bone-marrow transplantation. In eight individuals, CSF was taken before and 6-9 months after conditioning. CSF-sCD27 levels were compared with other MS and non-inflammatory neurological disease controls. Regarding the effect of stem-cell transplantation on CSF oligoclonal bands, the study analysed pooled data of this and four other international studies on stem-cell transplantation in MS.

RESULTS

CSF-sCD27 was significantly lower after the extremely immunoablative protocol. However, levels remained elevated compared with non-inflammatory controls and stayed within the range observed in other MS controls. The joint analysis of CSF oligoclonal bands demonstrated persistence of this immune abnormality in 88% of the reported cases (n = 34).

CONCLUSIONS

The persistence of CSF lymphocyte activation markers sCD27 and intrathecal oligoclonal IgG bands after maximum immunoablative treatment indicates that complete eradication of activated lymphocytes from the CNS has not been established. This is paralleled by disease progression observed in several studies on the effect of stem-cell transplantation in MS.

Circulating endothelial cells in oncology: pitfalls and promises

Adequate blood supply is a prerequisite in the pathogenesis of solid malignancies. As a result, depriving a tumour from its oxygen and nutrients, either by preventing the formation of new vessels, or by disrupting vessels already present in the tumour, appears to be an effective treatment modality in oncology. Given the mechanism by which these agents exert their anti-tumour activity together with the crucial role of tumour vasculature in the pathogenesis of tumours, there is a great need for markers properly reflecting its impact. Circulating endothelial cells (CEC), which are thought to derive from damaged vasculature, may be such a marker. Appropriate enumeration of these cells appears to be a technical challenge. Nevertheless, first studies using validated CEC assays have shown that CEC numbers in patients with advanced malignancies are elevated compared to healthy controls making CEC a potential tool for among other establishing prognosis and therapy-induced effects. In this review, we will address the possible clinical applications of CEC detection in oncology, as well as the pitfalls encountered in this process.

Imbalances in circulating lymphocyte subsets in Hu antibody associated paraneoplastic neurological syndromes

In paraneoplastic neurological syndromes (PNS) associated with small cell lung cancer (SCLC) and Hu antibodies, neuron-specific Hu antigens expressed by the tumour hypothetically trigger an immune response that cross-reacts with Hu antigens in the nervous system, resulting in tumour suppression and neuronal damage. To gain more insight into the hypothesized cell-mediated immune pathogenesis of these syndromes, we analysed the circulating lymphocyte subsets in untreated patients with SCLC, PNS and Hu antibodies (n = 18), SCLC without PNS (n = 19) and controls (n = 29) using flow cytometry. SCLC patients with PNS had a variety of imbalances within their circulating lymphocyte subsets as compared with SCLC patients without PNS and healthy controls: (i) a lymphopenia of the major subsets (i.e. B, CD4+ and CD8+ T lymphocytes); (ii) increased proportions of activated CD4+ and CD8+ T cells; (iii) reduced numbers of terminally differentiated effector CD8+ T cells and cells with a cytotoxic T-cell phenotype (CD56+ and CD57+). Although indirect, our data provide further support for the involvement of T cells in the pathogenesis of Hu antibody associated PNS.

CSF flow cytometry greatly improves diagnostic accuracy in CNS hematologic malignancies

OBJECTIVE

To assess the diagnostic accuracy of flow cytometric immunophenotyping in comparison with classic cytomorphology for diagnosing CNS localizations of hematologic malignancies, and to evaluate the implications of CSF pleocytosis and protein content in this context.

METHODS

We reviewed the results of diagnostic evaluations of all CSF samples analyzed for localization of a hematologic malignancy between 2001 and 2004 at our center.

RESULTS

A total of 1,054 samples from 219 patients were available for analysis. Sixty patients had a CSF localization diagnosed by positive flow cytometry, cytomorphology, or both. The first sample was positive by flow cytometry in 44 (73%) patients, by cytomorphology in 19 (32%). Four first samples were positive by cytomorphology but negative by flow cytometry. Patients with positive cytomorphology had more frequent clinical symptomatology (95% vs 58%) and CSF pleocytosis (84% vs 25%), and tended to a poorer progression-free survival than patients with positive flow cytometry only. OR for CNS localization in case of CSF pleocytosis was 10.1 (95% CI 4.9 to 20.8); OR for CNS localization in case of elevated protein content was 2.9 (95% CI 1.5 to 5.4). Nevertheless, 26 of 137 (19%) patients with normal cell count and protein concentration had a CNS localization.

CONCLUSIONS

The diagnostic value of flow cytometry is more than twice that of cytomorphology. However, cytomorphologic examination of the CSF has additional diagnostic and possibly prognostic value, and should still be performed in conjunction with flow cytometry.

Discriminant function analysis as decision support system for the diagnosis of acute leukemia with a minimal four color screening panel and multiparameter flow cytometry immunophenotyping

Despite several recommendations for standardization of multiparameter flow cytometry (MFC) the number, specificity and combinations of reagents used by diagnostic laboratories for the diagnosis and classification of acute leukemias (AL) are still very diverse. Furthermore, the current diagnostic interpretation of flow cytometry readouts is influenced arbitrarily by individual experience and knowledge. We determined the potential value of a minimal four-color combination panel of 13 monoclonal antibodies (mAbs) with a CD45/sideward light scatter-gating strategy for a standardized MFC immunophenotyping of the clinically most relevant subgroups of AL. Bone marrow samples from 155 patients with acute myeloid leukemia (AML, n=79), B-cell precursor acute lymphoblastic leukemia (BCP-ALL, n=29), T-cell precursor acute lymphoblastic leukemia (T-ALL, n=12) and normal bone marrow donors (NBMD, n=35) were analyzed. A knowledge-based learning algorithm was generated by comparing the results of the minimal panel with the actual diagnosis, using discriminative function analysis. Correct classification of the test sample according to lineage, that is, BCP-ALL, T-ALL, AML and differentiation of NBMD was achieved in 97.2% of all cases with only six of the originally applied 13 mAbs of the panel. This provides evidence that discriminant function analysis can be utilized as a decision support system for interpretation of flow cytometry readouts.

Process validation and clinical evaluation of a protocol to generate gene-modified T lymphocytes for imunogene therapy for metastatic renal cell carcinoma: GMP-controlled transduction and expansion of patient's T lymphocytes using a carboxy anhydrase IX-specific scFv transgene

BACKGROUND

Adoptive transfer of autologous T cells that are gene-transduced to express Ag-specific receptors represents an experimental strategy to provide tumor-specific immunity to cancer patients. We studied this concept in patients with metastatic renal cell cancer (RCC) using retroviral transduction of T cells with a single-chain Ab-G250 chimeric receptor [scFv(G250)]. We describe the validation of our clinical protocol for gene transduction and expansion of human T lymphocytes.

METHODS

A batch of scFv(G250) transgene-containing retrovirus was produced under conditions of good manufacturing practice (GMP). In addition to quality control and safety testing of the virus batch, extensive potency testing was performed, i.e. assessment of its functional transduction efficiency in primary human T cells. Subsequently, the clinical gene transduction and cell-expansion protocol was subjected to a series of process validations and a clinical evaluation using T cells obtained from healthy donors and three RCC patients.

RESULTS

The clinical batch of scFv(G250) transgene-containing retrovirus met the quality and safety control criteria. Small-scale transductions yielded 62-92% scFv(G250)+ T cells and, at a clinical scale, 50-84% transduction efficiencies were obtained. Patient and healthy donor T cells showed similar expansion potencies, and also yielded similar levels of scFv(G250)-mediated immune functions, i.e. specific cytolysis of G250-ligand expressing RCC cells and production of IFN-gamma upon stimulation with such cells. All T cell cultures were free of replication competent retroviruses.

DISCUSSION

We have shown that the validated batch of scFv(G250) transgene-containing retrovirus in combination with our GMP T-cell transduction and expansion protocol successfully generates clinically relevant numbers of functional scFv(G250) gene-modified T cells for patient treatment.

T-lymphocyte reconstitution following rigorously T-cell-depleted versus unmodified autologous stem cell transplants

We compared the kinetics of T-cell recovery after extensive ex vivo and in vivo T-cell depleted autologous stem cell transplantation (SCT) for multiple sclerosis (MS; n=8) with unmodified SCT for hematological malignancies (HM; n=39). Both patient group showed a very protracted recovery of 'naive' CD4(+), 45R0(-) ( approximately CD45RA(+)) T-cells. Within the 'primed' CD4(+), 45R0(+) T-cells, the 'central memory' cells expressing the CD62L and CD27 markers were the slowest to recover. The repopulating T-cells were highly activated, as shown by increased expression of HLA-DR and the apoptosis marker CD95. The capability of CD4(+) and CD8(+) T-cells to produce IFN-gamma, IL-2 and TNF-alpha had reached normal ranges from 2 months post SCT onwards. Unexpectedly, the kinetics of T-cell recovery between 3 and 12 months post transplant was similar in T-depleted and unmodified SCT. Before SCT, the HM patients showed lymphopenia of all T-cell subsets, upregulated HLA-DR and CD95 expression and increased cytokine responses. We suggest that the similar kinetics of T-cell recovery in the two patient groups may be explained by the susceptibility to apoptosis of the activated CD4(+) T-cells in the autografts of the HM patients. This susceptibility to apoptosis would interfere with a swift and sustained CD4(+) T-cell regeneration post SCT.

Parallel Detection of Transduced T Lymphocytes After Immunogene Therapy of Renal Cell Cancer by Flow Cytometry and Real-Time Polymerase Chain Reaction: Implications for Loss of Transgene Expression

We have started a phase I/II immunogene therapy study of metastatic renal cell cancer (RCC), using autologous T lymphocytes transduced ex vivo with a gene encoding a single-chain receptor based on the monoclonal antibody (mAb) G250 [scFv(G250)]. G250 recognizes carbonic anhydrase IX, which is overexpressed by RCC cells. We have developed and validated flow cytometric and real-time polymerase chain reaction (PCR) assays to quantitatively detect transduced T cells in patient blood. The flow assay was based on staining with the anti-G250 idiotype mAb NuH82 and showed a sensitivity of 0.06% scFv(G250)(1) cells within CD3(1) T cells. The real-time PCR method showed a sensitivity of 14 copies of scFv(G250) DNA per 100 ng of total DNA, which enabled detection of 0.008% scFv(G250)(1) T cells within leukocytes. Both assays were further validated for their specificity and reproducibility. When applied to blood samples from three RCC patients treated with intravenous infusions of scFv(G250)(1) T cells, the kinetics of scFv(G250)(1) T cell counts as detected by flow cytometry were similar to those detected by real-time PCR, although PCR allowed detection of transduced T cells over a longer period of time (i.e., for patient 3, 7 versus 32 days, respectively). Interestingly, follow-up studies of patient 3 demonstrated that the number of circulating scFv(G250)(1) T cells remained fairly constant during the first 7 days posttreatment, whereas the number of gene copies increased during the same period of time. These results suggest loss of scFv(G250) membrane expression on adoptive transfer, which would have important implications for the antitumor efficacy of this form of immunogene therapy.

Phoenix-ampho outperforms PG13 as retroviral packaging cells to transduce human T cells with tumor-specific receptors: implications for clinical immunogene therapy of cancer

We have designed a transgene that encodes a scFv(G250) chimeric receptor, which is specific for carboxyanhydrase IX (G250-ligand, G250L), a molecule overexpressed by renal cell cancer (RCC). Retroviral transduction of this transgene into primary human T lymphocytes confers these cells with specific functional responses towards G250L-positive RCC cells. In preparation of a clinical phase (I/II) study in RCC patients, we set up a protocol for gene transduction and expansion of primary human T cells. For this purpose, we directly compared two packaging cell lines, that is, the GALV-pseudotyped MLV producing cell line PG13, and the MLV-A-producing cell line Phi-NX-Ampho (a.k.a. Phoenix-A). We generated and characterized stable scFv(G250)-positive clones of both PG13 and Phoenix cells and optimized the retrovirus production conditions. Transductions of primary human T cells yielded 30-60% scFv(G250)+ T cells using PG13-derived retrovirus versus up to 90% scFv(G250)+ T cells using Phoenix-derived retrovirus. The median number of transgene integrations per scFv(G250)+ T cell differed only 1.5-fold as determined by real-time PCR (mean number of integrations per T cell 2.6 and 3.7 for PG13 and Phoenix-based transductions, respectively). In addition, T cells transduced with Phoenix-derived retrovirus showed, on a per cell basis, 10-30% higher levels of scFv(G250)-mediated TNFalpha production and cytolysis of G250L+ RCC cells than T cells transduced with PG13-derived retrovirus. The improved functional transduction efficiency together with a limited increase in the number of integrations per recipient cell, made us select Phoenix clone 58 for our clinical immunogene therapy study.

An immunomagnetic epithelial tumor cell enrichment model for minimal residual disease detection of cytokeratin 8+ malignancies

Immunocytochemical detection of isolated tumor cells in peripheral blood and bone marrow is currently the most established method for monitoring early dissemination in epithelial cancer. In this study we used an immunomagnetic selection technique to develop an enrichment model for disseminated tumor cells in blood. Buffy coat cells spiked with varying numbers of BT-474 carcinoma cells were permeabilized and fixed, following which carcinoma cells were magnetically labelled with an anti-cytokeratin 8 mAb. Labelled cells were enriched by the use of magnetic columns. The eluted cytokeratin 8+ tumor cells were detected by flow cytometry and immunocytochemistry. Spiked samples were split and processed freshly in the immunomagnetic enrichment assay, as well as cryopreserved and processed in the assay after thawing. Enumeration of BT-474 cells demonstrated a detection limit of one BT-474 cell in 1.0 x 10(7) leukocytes in both fresh and cryopreserved-thawed samples. The pair wise comparison showed a significantly higher recovery of spiked BT-474 cells from freshly processed samples than from cryopreserved and thawed samples (57% vs 21%). Viability tests suggested that this outcome might be due to a greater susceptibility of BT-474 cells than buffy coat cells to the used cryopreservation and thawing technique. Altogether our findings show that the performance of the immunomagnetic enrichment assay on fresh samples is satisfactory with a recovery rate of almost 60% and a sensitivity of 10(-7). However, performance of the assay on cryopreserved and thawed cells needs to be improved.

The value of crossmatch tests and panel tests as a screening tool to predict the outcome of platelet transfusion in a non-selected haematological population of patients

BACKGROUND AND OBJECTIVES

Alloantibodies against platelets can be detected by using different laboratory tests. Most of these tests, which use panel cells or antigens as a target, perform poorly in non-selected haematological patients. In relation to these tests, a crossmatch test of transfused platelets and patient's serum may be viewed as the standard and may be superior in predicting donor platelet destruction by alloimmunization.

MATERIALS AND METHODS

In 95 randomly selected thrombocytopenic patients with haematological malignancies, who were receiving leucodepleted blood products, 184 serum samples were studied in an in vitro crossmatch test by using the technique of the platelet immunofluorescence test (crossmatch-PIFT), in an in vivo crossmatch test detecting in vivo binding of immunoglobulins to transfused platelets according to the PIFT technique (in vivo-PIFT), in the indirect PIFT using five random donors as a target (panel-PIFT) and in an enzyme linked immunosorbent assay using immobilized human leucocyte antigens (HLAs) of 100 standardized donors (ELIHLA). The results of all these methods were related to the recovery at 1 and 16 h post-transfusion.

RESULTS

The results of the crossmatch-PIFT were not associated with platelet recovery at 1 and 16 h after transfusion. Even in a subgroup of patients, in whom predefined clinical factors were excluded, no association with platelet recovery was found. The results of the crossmatch-PIFT correlated with those of the in vivo-PIFT (P = 0.02); however, 35 (19%) discrepant results were identified between these tests. The results of the crossmatch-PIFT were not related to the panel-PIFT (P = 0.25), but did relate to those of the ELIHLA (P = 0.02), still revealing 36 (20%) discrepant results. None of the in vivo-PIFT, the panel-PIFT or the ELIHLA was associated with platelet recovery after 1 h, whilst only a positive panel-PIFT was associated with poor platelet recovery at 16 h after transfusion (P = 0.03).

CONCLUSIONS

In a population at low risk for alloimmunization, the correlation of test outcome and platelet recovery is poor. None of these crossmatch tests or screening tests was identified as superior to any other in this population.

Three-color flowcytometric analysis of mature and immature hematological malignancies. A guideline of the Dutch Foundation for Immunophenotyping of Hematological Malignancies (SIHON)

Multiparameter flowcytometry offers an insight into differentiation pathways, maturation stages and abnormal features of cell (sub)populations thus helping to establish and classify hematological malignancies. The Dutch Foundation for Immunophenotyping of Hematological Malignancies (SIHON) has formulated a guideline for a rapid screening followed by confirmation and classification in a standardized way. For this aim seven carefully composed monoclonal antibody combinations are elucidated for screening the test sample in a first phase. In this phase a relative frequency distribution of the cells will be established and a decision will be made about abnormal cells present, as well as their mature or immature state and the cell lineage they belong to. In a second phase, panels with cell lineage dependent monoclonal antibody combinations may be used to confirm and classify the abnormal cell population indicated in phase 1, as well as to establish the presence or absence of an abberant immunophenotype.

The use of CD38 expression by monoclonal B lymphocytes as a prognostic factor in B-cell chronic lymphocytic leukemia

In B-cell chronic lymphocytic leukemia (B-CLL) the Rai and Binet staging criteria are not always able to accurately predict the prognosis of each patient. Rapidly evolving, violent disease is often seen in the so-called "good-prognosis" group, which highlights the need of additional and more refined prognostic markers. Several of these markers are described in the literature, with varying abilities to predict patient survival. Among the promising prognostic markers is flowcytometric analysis of CD38 on the monoclonal B cells in CLL. Several studies have shown that expression of CD38 is associated with a decreased overall-, or progression free survival. CD38 expression may be analyzed as percentage positive cells or as antibodies bound per cell. Addition of CD38 to the flow cytometry antibody panel for B-CLL analysis is a relatively easy way to obtain important prognostic information.

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.

Adoptive immuno-gene therapy of cancer with single chain antibody [scFv(Ig)] gene modified T lymphocytes

Adoptive transfer of antigen-specific T cells has recently shown therapeutic successes in the treatment of viral infections and tumors. T cells specific for the antigen of interest can be generated in vitro, and adoptively transferred back to provide patients with large numbers of immune-competent T cells. Adoptive T cell therapy, however, is a patient-tailored treatment that unfortunately is not universally applicable to treat viral infections and tumors. We and others have demonstrated that the transfer of genes encoding antigen-specific receptors into T cells (i.e., genetic retargeting) represents an attractive alternative to induce antigen-specific immunity. Currently, we evaluate this concept in a clinical protocol to treat patients with metastatic renal cell cancer (RCC) using autologous RCC-specific gene-modified T lymphocytes.

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.

Crossover study of three methods for low-level white blood cell counting on two types of flow cytometer

BACKGROUND

Flow cytometric methods were previously shown to be preferable to microscopic and volumetric methods for counting residual white blood cells (WBCs). In this study, three flow cytometric, low-level WBC counting methods were cross compared using two flow cytometers.

METHODS

Double-filtered red cell and platelet concentrates were spiked with different amounts of WBC to obtain panels of unspiked and 0.3, 1.0, 3.3, and 10.0 WBC/microl. The methods of BD Biosciences (BDB), Beckman-Coulter (BC), and an in-house method were performed on flow cytometers from BDB and BC. Samples were measured in ninefold. We required that (a) r(2) be at least 0.98 (linearity), (b) at least 80% of observations fell within 20% of expected values (accuracy), and (c) the coefficients of variation be at least 20% (precision) for samples containing at least 3.3 WBC/microl.

RESULTS

For the red cell panel, our requirements were met by the BDB method on both flow cytometers and by the BC and in-house methods on the BDB flow cytometer only. For the platelet panel, our requirements were met on all combinations of methods and flow cytometers, except for the in-house method on the BDB flow cytometer. Intra-assay variation was lowest for the BDB method, irrespective of the type of flow cytometer used.

CONCLUSION

Based on accuracy and precision, the BDB method on the BDB flow cytometer produced the best results for counting low-level WBCs.

Visual scoring versus histogram subtraction of in vivo binding of immunoglobulins against platelets after transfusion

BACKGROUND

We developed a technique, in vivo binding of immunoglobulins in the platelet immunofluorescence test (IVBI-PIFT), that detects immunoglobulins bound in vivo to transfused platelets. The visually scored results of this technique, however, are susceptible to interobserver variation. We describe a more objective method to generate results in IVBI-PIFT.

METHODS

We studied 201 samples in 120 patients with hematologic malignancies in the IVBI-PIFT. Histogram subtraction, i.e., fluorescence (anti-immunoglobulin G and fluorescein isothiocyanate) histogram before platelet transfusion subtracted from the histogram after platelet transfusion, was compared with visual scoring (pattern 1: no enhanced fluorescence before and after transfusion; pattern 2: enhanced fluorescence before and after platelet transfusion; pattern 3: enhanced fluorescence before transfusion; pattern 4: enhanced fluorescence after transfusion, interpreted as alloimmunization). After histogram subtraction, the number of remaining events (events post substraction, EPS) and the mean amount of fluorescence of these remaining events (mean channel post substraction, MCPS) were used and compared with the visual scoring and with platelet survival after transfusion.

RESULTS

In 26 (13%) of the 201 samples studied in the IVBI-PIFT, fewer than three of five observers agreed on the visually scored pattern. In the 175 (87%) remaining samples, histogram subtraction showed a significant differentiation between pattern 4 and patterns 1 and 2 by using EPS, whereas patterns 4 and 3 were distinguished by using MCPS. The combination of EPS and MCPS differentiated best between pattern 4 and patterns 1, 2, and 3 (73% sensitivity, 96% specificity, 79% positive predictive value, and 95% negative predictive value). In contrast, the predictive value for platelet recovery after 1 and 16 h of pattern 4 from the visual scoring method and the results of histogram subtraction were poor.

CONCLUSION

This objective method of histogram subtraction correlated well with the visual scoring method of IVBI-PIFT.

Diagnostic potential of tetramer-based monitoring of cytomegalovirus-specific CD8+ T lymphocytes in allogeneic stem cell transplantation

Cytomegalovirus (CMV) infection remains a significant problem in allogeneic stem cell transplant (SCT) recipients despite the availability of effective antiviral drugs. This problem concerns patients which are unable to mount an effective T-lymphocyte response against CMV. Therefore, the development and use of tetramer technology to enumerate CMV-specific T cells will be valuable to identify these patients as early as possible. Here, we review clinical studies in which CMV-specific CD8(+) T cells have been monitored in allogeneic SCT recipients using tetramers in the context of similar studies that are based on functional assays of CMV-specific T cells. The results thus far warrant the further development of tetramer technology as a diagnostic tool to monitor CMV-specific T cells in SCT recipients and other groups of immunocompromised patients threatened by CMV.

Intracellular detection of Bcl-2 and p53 proteins by flow cytometry: comparison of monoclonal antibodies and sample preparation protocols

Several techniques have been proposed for flow cytometric evaluation of intracellular antigens. This approach is particularly important for detection at the single cell level of proteins which correlate to tumour progression. Bcl-2 and p53 are two of the most relevant proteins. In the present study we have compared five different cell fixation-permeabilisation protocols and nine fluorochrome-conjugated (FITC or PE) monoclonal antibodies (mAb): four mAb directed against Bcl-2 and five against p53. For detection of Bcl-2 we have analysed three Bcl-2 positive cell lines (K562, Daudi and MCF-7), and peripheral blood samples obtained from nine healthy subjects. To distinguish internal positive (lymphocytes) and negative control cells (granulocytes), it was necessary to perform simultaneous detection of surface and intracellular antigens. For detection of p53 three cell lines, two p53 positive (Raji and CEM) and one p53 negative (HL-60), were analysed. Using these cells we have performed a combined analysis of the efficiency of monoclonal antibodies and sample preparation techniques. In conclusion, clones 124-FITC and Bcl-2/100-PE (Bcl-2), and clones BP53,12-FITC and G59-12-PE (p53) provided the highest specific fluorescence intensity of the respective markers independent of cell preparation protocols. Importantly, our results show that mAb background may depend on the specific fixation/permeabilisation kit and that mAb titration using negative and positive control cells is essential to determine the specificity and the sensitivity of the mAb used.

Diagnostic and prognostic value of flow cytometric immunophenotyping in malignant hematological diseases

Flow cytometry is a diagnostic cell analysis technique with ever increasing applications in modern hematological practice. To date immunophenotyping of clonal hematological diseases represents one of the primary clinical applications of flow cytometry. Immunophenotyping of abnormal cells is now considered a fundamental tool to establish the cell lineage assignment and to obtain a more precise identification of the various cell subtypes. A number of observations have emerged showing strong association between specific immunophenotypes and genetic recurrent abnormalities underlying the malignant transformation, with prognostic value.

Increased levels of soluble CD27 in the cerebrospinal fluid are not diagnostic for leptomeningeal involvement by lymphoid malignancies

Soluble CD27 (sCD27) reportedly is a sensitive and specific marker for leptomeningeal involvement (LI) of CD27-expressing lymphoproliferations such as B-cell non-Hodgkin's lymphoma (B-NHL) or chronic B-lymphocytic leukemia (B-CLL). Because morphological analysis of cerebrospinal fluid (CSF) in patients suspected of LI is false negative in one-third of patients, a diagnostic marker for LI by B-NHL or B-CLL would be very valuable. sCD27 was determined in the first CSF sample from each of 102 unselected patients submitted for (immuno)morphologic detection of malignant cells. The patients were considered to have LI if either (immuno)morphologic analyses showed tumor cells or if neuroradiological evaluation showed typical abnormalities consistent with LI. Patients were suspected of having LI if CSF samples revealed atypical lymphocytes and/or if clinical symptoms and signs suggestive of LI were present, but clinical follow-up was shorter than 3 months because of deterioration of the patient. LI was considered absent if (immuno)morphologic analyses of CSF samples were negative without evidence for LI during 3 months of clinical follow-up. In patients with chronic lymphoproliferative disorders [mainly B-non-Hodgkin's lymphoma (NHL)], sCD27 concentrations were significantly higher in the CSF samples of 16 patients with confirmed or suspected LI than in those of 46 patients without LI. However, sCD27 was also increased in a variety of other predominantly inflammatory neurological disorders including herpes simplex and zoster infections. The positive predictive value of sCD27 determination for LI was only 54%, but the negative predictive value was 92%. Normal sCD27 concentrations in CSF samples of patients with chronic lymphoproliferation makes LI unlikely, but the determination of CSF sCD27 is not sufficiently specific to serve as a reliable tumor marker.

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.

Tetramer-based quantification of cytomegalovirus (CMV)-specific CD8+ T lymphocytes in T-cell-depleted stem cell grafts and after transplantation may identify patients at risk for progressive CMV infection

Recovery of cytomegalovirus (CMV)-specific T-cell-mediated immunity after allogeneic hematopoietic stem cell transplantation (SCT) is critical for protection against CMV disease. The study used fluorochrome-conjugated tetrameric complexes of HLA-A2 molecules loaded with the immunodominant NLVPMVATV (NLV) peptide derived from the CMV protein pp65 to quantify A2-NLV-specific CD8+ T cells in partially T-cell-depleted grafts administered to 27 HLA-A*0201+ patients and to monitor recovery of these T cells during the first 12 months after SCT. None of the 9 CMV-seronegative patients became infected with CMV, whereas 14 of 18 CMV-seropositive patients developed CMV antigenemia after SCT. CMV-seropositive recipients of grafts from CMV-seronegative donors required more preemptive treatment with ganciclovir (GCV) than those of grafts from CMV-seropositive donors (3 [1-6] versus 1 [0-3] courses, respectively; P =.009). The number of A2-NLV-specific CD8+ T cells in the grafts correlated inversely with the number of preemptive GCV courses administered (r = -0.61; P =.01). None of the 9 CMV-seronegative patients mounted a CMV-specific immune response as measured by monitoring A2-NLV-specific CD8+ T cells after SCT. Thirteen of 14 CMV-seropositive patients without CMV disease recovered these T cells. In spite of preemptive GCV treatment, CMV disease developed in 4 patients, who all failed to recover A2-NLV-specific CD8+ T cells after SCT (P =.002). Thus, enumeration of HLA-restricted, CMV-specific CD8+ T cells in the grafts and monitoring of these T cells after SCT may constitute a rapid and sensitive tool to identify SCT recipients at risk for developing CMV disease.

Epstein-Barr virus (EBV) reactivation is a frequent event after allogeneic stem cell transplantation (SCT) and quantitatively predicts EBV-lymphoproliferative disease following T-cell--depleted SCT

Reactivation of the Epstein-Barr virus (EBV) after allogeneic stem cell transplantation (allo-SCT) may evoke a protective cellular immune response or may be complicated by the development of EBV-lymphoproliferative disease (EBV-LPD). So far, very little is known about the incidence, recurrence, and sequelae of EBV reactivation following allo-SCT. EBV reactivation was retrospectively monitored in 85 EBV-seropositive recipients of a T-cell--depleted (TCD) allo-SCT and 65 EBV-seropositive recipients of an unmanipulated allo-SCT. Viral reactivation (more than 50 EBV genome equivalents [gEq]/mL) was monitored frequently by quantitative real-time plasma polymerase chain reaction until day 180 after SCT. Probabilities of developing viral reactivation were high after both unmanipulated and TCD-allogeneic SCT (31% +/- 6% versus 65% +/- 7%, respectively). A high CD34(+) cell number of the graft appeared as a novel significant predictor (P =.001) for EBV reactivation. Recurrent reactivation was observed more frequently in recipients of a TCD graft, and EBV-LPD occurred only after TCD-SCT. High-risk status, TCD, and use of antithymocyte globulin were predictive for developing EBV-LPD. Plasma EBV DNA quantitatively predicted EBV-LPD. The positive and negative predictive values of a viral load of 1000 gEq/mL were, respectively, 39% and 100% after TCD. Treatment-related mortality did not differ significantly between TCD and non-TCD transplants, but the incidence of chronic graft-versus-host disease was significantly less in TCD patients. It is concluded that EBV reactivation occurs frequently after TCD and unmanipulated allo-SCT, especially in recipients of grafts with high CD34(+) cell counts. EBV-LPD, however, occurred only after TCD, and EBV load quantitatively predicted EBV-LPD in recipients of a TCD graft. (Blood. 2001;98:972-978)

Molecular quantification of viral load in plasma allows for fast and accurate prediction of response to therapy of Epstein-Barr virus-associated lymphoproliferative disease after allogeneic stem cell transplantation

Epstein-Barr virus lymphoproliferative disease (EBV-LPD) following allogeneic stem cell transplantation (allo-SCT) has a poor prognosis. We used a sensitive real-time polymerase chain reaction (PCR) assay for quantitative detection of EBV-DNA in plasma and serially measured EBV-DNA levels to assess the response to treatment in allo-SCT recipients with EBV-LPD. Fourteen allo-SCT recipients with EBV-LPD who received a T cell-depleted (TCD) sibling (n = 5) or matched unrelated donor (n = 9) graft were monitored from the time of EBV-LPD diagnosis, during therapy and assessment of clinical response. Seven patients had complete responses of EBV-LPD to therapy, of whom 21% (3 out of 14) survived beyond 6 months from EBV-LPD diagnosis. Clinically responding patients showed a rapid decline of EBV-DNA plasma levels within 72 h from the start of therapy. In contrast, all clinical non-responders showed an increase of EBV-DNA levels. Absolute EBV-DNA levels at the time of EBV-LPD diagnosis did not predict for response, but the pattern of EBV-DNA levels within 72 h from the start of therapy (> 50% decrease versus increase) strongly predicted for clinical response (P = 0.001). Quantitative monitoring of EBV-DNA levels from the start of and during therapy for EBV-LPD rapidly and accurately predicts for response to therapy as early as within 72 h. It may thus provide a powerful tool to adjust and select treatment in individuals with EBV-LPD following allo-SCT.

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.

SIHONSCORE: a scoring system for external quality control of leukaemia/lymphoma immunophenotyping measuring all analytical phases of laboratory performance

For the diagnosis of leukaemia and leukaemic lymphoma, clinicians frequently have to rely on the results of immunophenotyping. To improve the quality of these results, the Dutch Foundation for Immunophenotyping of Haematological Malignancies (SIHON) initiated external quality rounds in 1986. Over a period of more than 10 years, this has led to improvements in the interpretation of immunophenotyping results. However, the evaluation of results focused mainly on the correctness of the interpretation of the immunophenotypical data, leaving the preceding analytical phases unevaluated. Therefore, in 1996 SIHON developed a more comprehensive scoring system, called SIHONSCORE, covering all three phases of immunophenotyping, namely the pre-analytical (i.e. choice of the staining panels), analytical (i.e. the technical part consisting of sample preparation, data acquisition and analysis) and the post-analytical phase (i.e. the interpretation) of the laboratory process. Here, we report how SIHONSCORE was successfully applied to three consecutive external quality rounds consisting of a total of nine different cases tested. For laboratory certification, participation in external quality control programmes is required. Evidently, criteria are needed to define the minimum acceptable performance of a certified laboratory. With SIHONSCORE, a useful instrument is obtained evaluating all phases of the performance of laboratories in leukaemia and lymphoma immunophenotyping.

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 for evaluation of graft adequacy of peripheral blood stem cell grafts, and is also useful in planning the apheresis sessions necessary to obtain these grafts. The state-of-the-art method to enumerate CD34+ cells makes use of a multiparameter definition of HPC based on their light scatter characteristics and dim expression of CD45, and the use of counting beads to derive the concentration of CD34+ cells directly from the flow cytometric assessment. This method can be extended with a viability stain and additional markers for further immunological characterization of CD34+ cells, and has been successfully implemented in multicenter trials. Thus, the lower threshold of a safe HPC graft in terms of short- and long-term hematopoiesis may be more accurately defined.

Cytofluorometric methods for assessing absolute numbers of cell subsets in blood. European Working Group on Clinical Cell Analysis

The enumeration of absolute levels of cells and their subsets in clinical samples is of primary importance in human immunodeficiency virus (HIV)+ individuals (CD4+ T- lymphocyte enumeration), in patients who are candidates for autotransplantation (CD34+ hematopoietic progenitor cells), and in evaluating leukoreduced blood products (residual white blood cells). These measurements share a number of technical options, namely, single- or multiple-color cell staining and logical gating strategies. These can be accomplished using single- or dual-platform counting technologies employing cytometric methods. Dual-platform counting technologies couple the percentage of positive cell subsets obtained by cytometry and the absolute cell count obtained by automated hematology analyzers to derive the absolute value of such subsets. Despite having many conceptual and technical limitations, this approach is traditionally considered as the reference method for absolute cell count enumeration. As a result, the development of single-platform technologies has recently attracted attention with several different technical approaches now being readily available. These single-platform approaches have less sources of variability. A number of reports clearly demonstrate that they provide better coefficients of variation (CVs) in multicenter studies and a lower chance to generate aberrant results. These methods are therefore candidates for the new gold standard for absolute cell assessments. The currently available technical options are discussed in this review together with the results of some cross-comparative studies. Each analytical system has its own specific requirements as far as the dispensing precision steps are concerned. The importance of precision reverse pipetting is emphasized. Issues still under development include the establishment of the critical error ranges, which are different in each test setting, and the applicability of simplified low-cost techniques to be used in countries with limited resources.