Low end-tidal CO2 as a real-time severity marker of intra-anaesthetic acute hypersensitivity reactions.

BACKGROUND: Prompt diagnosis of intra-anaesthetic acute hypersensitivity reactions (AHR) is challenging because of the possible absence and/or difficulty in detecting the usual clinical signs and because of the higher prevalence of alternative diagnoses. Delayed epinephrine administration during AHR, because of incorrect/delayed diagnosis, can be associated with poor prognosis. Low end-tidal CO2 (etCO2) is known to be linked to low cardiac output. Yet, its clinical utility during suspected intra-anaesthetic AHR is not well documented. METHODS: Clinical data from the 86 patients of the Neutrophil Activation in Systemic Anaphylaxis (NASA) multicentre study were analysed. Consenting patients with clinical signs consistent with intra-anaesthetic AHR to a neuromuscular blocking agent were included. Severe AHR was defined as a Grade 3-4 of the Ring and Messmer classification. Causes of AHR were explored following recommended guidelines. RESULTS: Among the 86 patients, 50% had severe AHR and 69% had a confirmed/suspected IgE-mediated event. Occurrence and minimum values of arterial hypotension, hypocapnia and hypoxaemia increased significantly with the severity of AHR. Low etCO2 was the only factor able to distinguish mild [median 3.5 (3.2;3.9) kPa] from severe AHR [median 2.4 (1.6;3.0) kPa], without overlap in inter-quartile range values, with an area under the receiver operator characteristic curve of 0.92 [95% confidence interval: 0.79-1.00]. Among the 41% of patients who received epinephrine, only half received it as first-line therapy despite international guidelines. CONCLUSIONS: An etCO2 value below 2.6 kPa (20 mm Hg) could be useful for prompt diagnosis of severe intra-anaesthetic AHR, and could facilitate early treatment with titrated doses of epinephrine. CLINICAL TRIAL REGISTRATION: NCT01637220.

OC-06 - Pro-thrombotic biomarkers in pancreatic diseases: are they specific of cancer?

INTRODUCTION: Venous thrombo-embolic events (VTE) occur frequently in patients with pancreatic cancer and contribute to elevated morbidity and mortality. Clinical risk factors for thrombosis such as cancer stage and tumor grade have been clearly identified. Recently, several biomarkers have been proposed which may help identifying cancer patients at high risk of thrombosis. Those biomarkers have been studied in heterogeneous cohorts of patients with different cancer types. AIM: To compare pro-thrombotic biomarkers in pancreatic cancer and in chronic pancreatitis to determine whether these biomarkers are related to cancer or inflammation and to validate their association with thrombotic risk in a pancreatic cancer population. MATERIALS AND METHODS: 45 patients with pancreatic cancer, 49 with intraductal papillary mucinous tumor of the pancreas (IPMN), a precancerous lesion, and 50 with chronic pancreatitis were recruited. Plasma levels of factor VIII, D-dimers, thrombin-antithrombin complexes, soluble p-selectin, tissue factor-dependent procoagulant activity of MP (TF-MP), free Tissue Factor Pathway Inhibitor (TFPI) and extracellular DNA were measured. Thrombin generation triggered by 1pM of TF was evaluated with the Calibrated Automated Thrombogram assay. RESULTS: Levels of factor VIII, D-dimers, TF-MP, TFPI and extracellular DNA were significantly higher in cancer patients compared to IPMN or chronic pancreatitis (Table 1). Patients with metastatic cancer (n=27) presented higher levels of D-dimers (mean±sd 1.77±1.28 vs 0.80±0.96 µg/ml, p=0.004) and MP-TF (54.3±53.2 vs 15.8±10.4 fM, p=0.02) compared to patients with localized lesions (n=18). Among cancer patients, 42 were followed for a median duration of 187 days (min 21-max 802 days). VTE occurred in 10 (23%) patients. All had metastatic cancer at the time of thrombosis. Only D-dimers were significantly elevated in cancer patients with VTE compared to patients without VTE (median 1.85 vs 0.7 µg/ml, p=0.02). CONCLUSIONS: Elevation of factor VIII, D-dimers, TF-MP, TFPI and extracellular DNA seems to be related to cancer process, not to local or systemic inflammation as these parameters differentiate cancer from chronic pancreatitis. Interestingly, D-dimers and TF-MP are related to the disseminated cancer stage, suggesting that vascular invasion is a prerequisite to the release of TF-MP from the primary tumor into the bloodstream and to coagulation activation. However, only D-dimers are associated with the occurrence of future VTE. We propose that D-dimers could be a useful tool to predict thrombotic events in pancreatic cancer patients. This should be confirmed in a larger population.

Diagnosis of plasma cell leukaemia: findings of the UK NEQAS for Leucocyte Immunophenotyping scheme.

The diagnosis of plasma cell leukaemia, a rare disorder with an aggressive clinical course and poor prognosis, is not always straightforward and may be dependent on the results of immunophenotyping. Samples from two cases of plasma cell leukaemia have been issued by the UK NEQAS for Leucocyte Immunophenotyping Scheme during the last 5 years and on each occasion a significant number of laboratories failed to make the correct diagnosis. The details of the two samples issued and the results of both surveys are presented. The data highlights the need to adhere to guidelines for immunophenotyping, with respect to using the correct antibody panels, the importance of data interpretation in conjunction with morphological appearance as well as the need to participate in external quality assurance schemes.

Evaluation of leukocyte stabilisation in TransFix-treated blood samples by flow cytometry and transmission electron microscopy.

In this report, we have evaluated the effects of a TransFix-based stabilisation technique on leukocyte scatter characteristics, immunophenotyping, membrane permeability, absolute cell counting and morphology to extend previously reported flow cytometric data focused on the lymphocyte population. We show that scatter characteristics, immunophenotyping and absolute cell counting are well preserved, particularly in the lymphocyte population. Nevertheless, a general increase in membrane permeability, evaluated by propidium iodide (PI) uptake, was observed in TransFix-treated leukocyte subsets. Ultrastructural observations show selective morphological preservation (up to 10 days of storage) of lymphocytes and, to a lesser extent, of monocytes. In contrast, granulocytes have necrosis-like features, although the plasma membrane seems well preserved. Therefore, electron microscopy observations reflect modifications induced in different cell populations as evidenced by flow cytometry (FC). The data indicate that this short-term stabilisation method is particularly suitable for the analysis of human lymphocytes and it is a good procedure for quality control programmes for inter- and intra-laboratory performance evaluation; good results are obtained with respect to antigen definition and absolute cell counting procedures. Any apoptotic pathways in leukocyte subsets are blocked for at least 10 days.

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.

Affordable CD4+ T cell counts by flow cytometry. II. The use of fixed whole blood in resource-poor settings.

We tested the feasibility and precision of affordable CD4+ T cell counting in resource-poor settings using a recently standardised fixative, TransFix in whole blood (WB) by flow cytometry (FCM). The precision of the assays was established under optimal conditions for single-platform FCM such as the volumetric CytoronAbsolute and the bead-based FACSCan. Fresh WB samples from HIV-seropositive and seronegative patients were tested in Tanzania and South Africa, fixed and sent to the UK for reanalysis 7 days later. Correlation, bias and limits of agreements were analysed by linear regression and the Bland-Altman test. Absolute CD4+ T cell counts remained stable for at least 10 days when TransFix was added to WB in 1:10 dilution at 20-25 degrees C, and for 7 days when added in 1:10 or 1:5 dilution to samples stored to mimic 'tropical' conditions at 37 degrees C. Higher temperatures such as 42 degrees C were tolerated for only short periods since the recovery had decreased to 63% by day 3. The reproducibility of lymphocyte subset analysis remained unchanged by TransFix with coefficient of variations <6% for all T cell subsets. Absolute CD4+ T cell counts and CD4+ T cell % values on fixed samples in the UK showed a high correlation with the results using fresh samples in Tanzania (r=0.993 and 0.969, respectively) and with the samples handled in Johannesburg (r=0.991 and 0.981) with minimal bias. Primary CD4 gating using only a single CD4 antibody also remained accurate in TransFixed samples (r=0.999). Thus, TransFix permits optimal fixation and transport of WB samples in the developing world for FCM to local regional laboratories and for quality assurance in international centres. When used together with inexpensive primary CD4 gating, TransFix will allow reliable and affordable CD4+ T cell counting by FCM in resource-poor settings.

Low level leucocyte counting: a critical variable in the validation of leucodepleted blood transfusion components as highlighted by an external quality assessment study.

Leucocyte counts of < 5 x 106 per blood transfusion product are currently recommended in the UK in order to reduce transfusion-related infections and febrile reactions. Routine leucocyte depletion, however, requires the development of reliable internal and external quality assurance (EQA) programmes. We report preliminary findings from the UK NEQAS for Low-Level Leucocyte Counting from 18 UK Transfusion Centres over a four month period. Data analysis showed that the IMAGN 2000 had the lowest CVs (range 7.5-36%, mean 16.7) for samples with counts of 5-30 cells/microl when compared to the flow cytometric (range 13.8-88%, mean 29.5) and Nageotte methods (range 20.6-117%, mean 61.8). In addition, laboratories using commercial nuclear stains (LeucoCOUNTTM) had consistently lower CVs than those using 'in-house' propidium iodide staining methods. Important differences in flow cytometric gating strategies were also identified. This study highlights the current variability in low level leucocyte counting, especially within the critical range of 5-30 cells/microl (equating to < 5 x 106/l). The acceptance of consensus protocols, including gating strategies and nuclear staining techniques, is required to reduce the observed interlaboratory variation. Finally, we demonstrate that stabilized blood preparations can be successfully used to provide a national/international low-level leucocyte EQA scheme.

Reduction of intra- and interlaboratory variation in CD34+ stem cell enumeration using stable test material, standard protocols and targeted training. DK34 Task Force of the European Working Group of Clinical Cell Analysis (EWGCCA).

The European Working Group on Clinical Cell Analysis (EWGCCA) has, in preparation for a multicentre peripheral blood stem cell clinical trial, developed a single-platform flow cytometric protocol for the enumeration of CD34+ stem cells. Using this protocol, stabilized blood and targeted training, the EWGCCA have attempted to standardize CD34+ stem cell enumeration across 24 clinical sites. Results were directly compared with participants in the UK National External Quality Assessment Scheme (NEQAS) for CD34+ Stem Cell Quantification that analysed the same specimens using non-standardized methods. Two bead-counting systems, Flow-Count and TruCount, were also evaluated by the EWGCCA participants during trials 2 and 3. Using Flow-Count, the intralaboratory coefficient of variation (CV) was

Standardization of lymphocyte antibody binding capacity - a multi-centre study.

As quantitative flow cytometry is being increasingly used to characterize non-malignant and malignant disorders, interlaboratory standardization becomes an important issue. However, the lack of standardized methods and process controls with predefined antibody binding capacity values, limits direct interlaboratory comparison. The present study has addressed these issues using a stable whole blood product and a standardized antigen quantification protocol. It was demonstrated that: (i) a standard technical protocol can result in a high degree of interlaboratory concordance; (ii) interlaboratory variation of less than 12% can be achieved for CD4 antibody binding capacity values; and (iii) stable whole blood can be used as a process control with predefined antibody binding capacity values. Furthermore, using such an approach, a normal range was established for CD3, CD4 CD8 and CD19. These antigens appear to be expressed in a hierarchical manner, a factor that could be used as a procedural quality control measure.

Absolute CD4+ T-lymphocyte and CD34+ stem cell counts by single-platform flow cytometry: the way forward.

To determine the potential advantage of single-platform technology in the enumeration of CD4+ T lymphocyte and CD34+ stem cells, data has been analysed from the UK NEQAS for Leucocyte Immunophenotyping schemes. The inter-laboratory CVs for CD4+ T lymphocyte counts were consistently lower for single-platform (mean 13.7%, range 10-18.3%) compared to dual-platform methodology (mean 23.4%, range 14.5-43.7%). Subgroup analysis of single-platform users demonstrated mean overall inter-laboratory CVs of 17.2%, 13% and 7.1% for the FlowCount, TruCount and volumetric approach respectively. The lowest inter-laboratory CVs obtained for a single sample by each single platform approach were 4% (TruCount), 4.4% (volumetric), 4.6% (FACSCount) and 12.7% (FlowCount). Similarly, the mean inter-laboratory CV for CD34+ stem cell enumeration using non-standardized single-platform approaches was 18.6% (range 3.1-36.9%) compared to 28.6% (range 19-44.2%) for the dual-platform technology. Our results suggest absolute cell subset enumeration should be performed by single-platform technology and that such an approach should improve the quality control of multi-centre clinical trial data for CD4+ T lymphocyte and CD34+ stem cells.

Quality assessment of CD34+ stem cell enumeration: experience of the United Kingdom National External Quality Assessment Scheme (UK NEQAS) using a unique stable whole blood preparation.

CD34+ peripheral blood stem cell (PBSC) mobilization and harvesting has rapidly replaced autologous bone marrow as a source of stem cells for transplantation. Timing and adequacy of harvests rely upon the accurate enumeration of circulating CD34+ cells. However, previous EQA programmes have reported interlaboratory CVs as high as 284%, suggesting the need for greater standardization. In addition the routine use of fresh and/or frozen cells as analytes also introduces antigen instability as a variable factor. To circumvent this problem and achieve a true reflection of interlaboratory variation, we have used a novel whole blood preparation in which the antigenic profiles of PBSCs, as determined by flow cytometry, are retained for > 200 d. This international scheme, currently the largest in the world, distributes aliquots of stabilized whole blood bi-monthly to 91 laboratories in 20 countries (44 U.K., 47 overseas). Participants are required to determine the percentage and absolute values for CD34+ PBSCs using in-house techniques. Adopting such a preparation, a more accurate determination of interlaboratory variation has been possible when compared to previous EQA studies, with CVs as low as 22% and 24% for percentage and absolute counts. In addition the programme has established that a wide range of methods are in routine use, emphasizing the urgent requirement for national/international consensus guidelines.

Determination of leucocyte antibody binding capacity (ABC): the need for standardization.

The flow cytometric determination of antigen density, or cellular antibody binding capacity, is now an accepted technique for the characterization of cells in health and disease. In HIV infection, for example, antigen density changes in CD38 expression may be an important indicator of disease progression. Our experience of using one such method, Quantum Simply Cellular, which measures antibody binding capacity (ABC), has highlighted several technical factors which can affect the results. We report the influence of pH, incubation temperature and time, antibody fluorochrome and titre, as well as lysing reagent (FACS Lysing Solution v. Ortho-mune Lysing Reagent) on the ABC of anti-CD3, CD4 and CD8 of normal lymphocytes. In addition, the effect of single, double or triple-staining was assessed. The results indicate that the ABC values are influenced by all the variables studied. The pH range tested (6.0-9.0) demonstrated that pH 7.4 gave maximal binding. Furthermore, temperature also influenced the pH of the two lysing solutions, and thus potentially the ABC. Antibody concentration, fluorochrome and staining technique are also important factors with an observed difference of up to 458,855 ABC between the various fluorochromes. In addition a maximal difference of 130,119 ABC was observed between single and triple staining techniques. In conclusion, if antigen quantification is to be used in the clinical setting, an internationally standardized method is required to ensure the reproducibility of results from centre to centre. Our data suggests that single staining, using fluorescein isothiocynate (FITC) conjugated antibodies with all reagents at pH 7.4 + 0.1, with incubation and lysing carried out at 20 + 1 degrees C, could be used as a 'benchmark' method for ABC determination using the QSC system.

Evaluation of a novel stable whole blood quality control material for lymphocyte subset analysis: results from the UK NEQAS immune monitoring scheme.

The UK NEQAS immune Monitoring Scheme (UK NEQAS) evaluates the performance of laboratories routinely performing T-lymphocyte subset analysis on HIV-infected individuals. The scheme originally issued fresh whole blood, but a significant problem was that of analyte stability, especially 36 h postphlebotomy. To circumvent this problem, we have developed a novel stabilisation procedure that ensures retention of leucocyte light scatter and immunological staining characteristics for up to 300 days. In addition, the stabilised whole blood preparation is fully compatible with flow cytometer technology, incorporating either whole blood lysis or "no wash, no lyse" techniques. The ranges of interlaboratory coefficient of variation for the stabilised material are now tighter than those previously obtained with fresh whole blood. Development of this novel material has enabled overseas laboratories to participate in the UK NEQAS immune Monitoring Scheme and could in the future lead to the production of reference and/or calibration reagents for leucocyte immunophenotyping.

Circulating CD20dim T-lymphocytes increase with age: evidence for a memory cytotoxic phenotype.

The CD20 antigen has been regarded as a B lineage specific, 35 kDa, non-glycosylated membrane phosphoprotein, which functions as either a Ca2+ ion channel or as a regulatory protein of such a channel. Weak expression of CD20 (CD20dim), however, has recently been reported on a sub-population of T lymphocytes. We present results which confirm the existence of a CD20dim T lymphocyte population and show that such cells have a reduced antibody-binding capacity, when compared to CD20bright B-cells (10337 +/- 642 and 346311 +/- 24264 respectively). In addition, CD20dim cell counts vary with age, with the highest levels occurring in octogenarians: cord blood 0.3 +/- 0.1% (n = 13), 20-60 year-old group 2.1 +/- 1.1% (n = 18) and individuals > or = 61 years of age 6.9 +/- 3.2% (n = 10) (P < 0.001). Further characterization of CD20dim T cells, using three colour flow cytometry, demonstrated a predominantly memory cytotoxic phenotype, in that the cells were CD8+CD28+CD45RO+T-CR alpha beta +CD38-HLA-DR-.