Specialist integrated haematological malignancy diagnostic services: an Activity Based Cost (ABC) analysis of a networked laboratory service model

AIMS

Specialist Integrated Haematological Malignancy Diagnostic Services (SIHMDS) were introduced as a standard of care within the UK National Health Service to reduce diagnostic error and improve clinical outcomes. Two broad models of service delivery have become established: 'co-located' services operating from a single-site and 'networked' services, with geographically separated laboratories linked by common management and information systems. Detailed systematic cost analysis has never been published on any established SIHMDS model.

METHODS

We used Activity Based Costing (ABC) to construct a cost model for our regional 'networked' SIHMDS covering a two-million population based on activity in 2011.

RESULTS

Overall estimated annual running costs were £1 056 260 per annum (£733 400 excluding consultant costs), with individual running costs for diagnosis, staging, disease monitoring and end of treatment assessment components of £723 138, £55 302, £184 152 and £94 134 per annum, respectively. The cost distribution by department was 28.5% for haematology, 29.5% for histopathology and 42% for genetics laboratories. Costs of the diagnostic pathways varied considerably; pathways for myelodysplastic syndromes and lymphoma were the most expensive and the pathways for essential thrombocythaemia and polycythaemia vera being the least.

CONCLUSIONS

ABC analysis enables estimation of running costs of a SIHMDS model comprised of 'networked' laboratories. Similar cost analyses for other SIHMDS models covering varying populations are warranted to optimise quality and cost-effectiveness in delivery of modern haemato-oncology diagnostic services in the UK as well as internationally.

A unified definition of clinical resistance/intolerance to hydroxyurea in essential thrombocythemia: results of a consensus process by an international working group

A widely accepted definition of resistance or intolerance to hydroxyurea (HU) in patients with essential thrombocythemia (ET) is lacking. An international working group (WG) was convened to develop a consensus formulation of clinically significant criteria for defining resistance/intolerance to HU in ET. To this aim, an analytic hierarchy process (AHP), a multiple-attribute decision-making technique, was used. The steps consisted of selecting the candidate criteria for defining resistance/intolerance; identifying the motivations that could influence the preference of the WG for any individual criterion; comparing the candidate criteria in a pair-wise manner; and grading them according their ability to fulfill the motivations. Every step in the model was derived by questionnaires or group discussion. The WG proposed that the definition of resistance/intolerance should require the fulfillment of at least one of the following criteria: platelet count greater than 600,000/micro l after 3 months of at least 2 g/day of HU (2.5 g/day in patients with a body weight over 80 kg); platelet count greater than 400,000/micro l and WBC less than 2500/micro l or Hb less than 10 g/dl at any dose of HU; presence of leg ulcers or other unacceptable muco-cutaneous manifestations at any dose of HU; HU-related fever.

A fatal case of disseminated zygomycosis associated with the use of blood glucose self-monitoring equipment

We report a fatal case of disseminated zygomycosis due to Cunninghamella bertholletiae in a 68-year-old man with myelodysplasia and type II diabetes mellitus, receiving desferrioxamine therapy for iron overload secondary to multiple transfusions. It is thought that he acquired the infection through the use of blood glucose self-monitoring equipment.

Aberrant methylation of the negative regulators RASSFIA, SHP-1 and SOCS-1 in myelodysplastic syndromes and acute myeloid leukaemia

Mutations in the receptor tyrosine kinase (RTK/RAS) signalling pathway frequently provide a proliferative signal in myeloid malignancies. However, the role of RASSF1A, SHP-1 and SOCS-1, negative regulators of RTK/RAS signalling, has not been extensively investigated in the myelodysplastic syndromes (MDS) or acute myeloid leukaemia (AML). This study employed methylation-specific polymerase chain reaction (MS-PCR) to determine if aberrant promotor methylation of RASSF1A, SHP-1 and SOCS-1 is involved in the pathogenesis of myeloid malignancies. Patients with MDS (n = 107), AML (n = 154) and juvenile myelomonocytic leukaemia (JMML, n = 5) were investigated, together with 15 normal controls. Primers were located in the promotor region of each gene as well as within exon 2 of SOCS-1. Methylation of RASSF1A was found in five of 55 (9%) MDS cases, but not in any of 57 AML cases studied. RASSF1A methylation was present in one case (20%) of JMML. SHP-1 methylation was present in 13 of 121 (11%) AML cases but was not found in MDS or JMML. SOCS-1 promoter methylation was present in eight of 74 (11%) MDS patients but was not seen in JMML or AML. Importantly, RAS mutations and RASSF1A and SOCS-1 methylation were mutually exclusive indicating that approximately 30% of MDS cases had a defect of the RTK/RAS pathway and its negative regulation. Finally, SOCS-1 exon 2 methylation may not be pathogenetically relevant, since it was detected in samples from normal individuals and did not correlate with promotor methylation.

Gains on 9p are common genomic aberrations in idiopathic myelofibrosis: a comparative genomic hybridization study

Ideopathic myelofibrosis (IMF) is a chronic myeloproliferative disorder resulting in bone marrow fibrosis as a consequence of growth factor release from clonal haematopoiesis. Conventional cytogenetic analysis identifies abnormalities in approximately a third of cases at diagnosis, although rarely uncovers unique, primary genetic events. We have used comparative genomic hybridization (CGH) to study 25 IMF cases and have compared the results with conventional cytogenetics. Metaphase cells were available for analysis in 13 cases, of which seven showed an abnormal karyotype. CGH chromosomal profiles showed imbalances in 21 of 25 cases. The most frequent aberrations were gains of 9p (12 cases), 2q (seven cases), 3p (seven cases), chromosome 4 (seven cases), 12q (seven cases), 13q (eight cases). The main losses were at 17q and occurred in six cases. The results for CGH and cytogenetics were matched for one case only. Investigation of IMF by CGH suggests that genomic aberrations are much more common than has been previously indicated by conventional cytogenetic analysis and occur in the majority of cases. Gains of 9p were the most frequent finding, occurring in 50% of patients and suggests that genes on 9p may play a crucial role in the pathogenesis of IMF.

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.

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.

The development of a national standardized approach for the enumeration of residual leucocytes in blood components

BACKGROUND AND OBJECTIVES

The UK Blood Transfusion Services implemented universal leucocyte depletion of the blood supply in November 1999. To provide statistical process monitoring of these processes, automated methods were introduced to count residual leucocytes (white blood cells) in blood components.

MATERIALS AND METHODS

Initially in the National Blood Service (NBS) England, protocols were standardized on the use of LeucoCount reagents with either Becton-Dickinson or Beckman Coulter flow cytometers.

RESULTS

Standardization of protocols resulted in a decreased intersite variability of red cell samples (from 36% to 9% at a level of 11 and 10 cells/ micro l, respectively), and 100% of sites (n = 11) fulfilled the validation criteria. However, we also evaluated the use of alternative reagents with the result that reagents from either Becton-Dickinson or Beckman Coulter, used on either a Becton-Dickinson or Beckman Coulter flow cytometer, passed our validation criteria.

CONCLUSIONS

It is critical to include samples from filtered products containing white blood cells in validations of leucocyte enumeration methodology, as results may differ between methods using these samples but not using spiked or fixed material. Standardized gating strategies and optimization methods for flow cytometers are critical for obtaining equivalent results with different reagents and instruments.

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.

UK NEQAS for leucocyte immunophenotyping: the first 10 years

In the past decade, cellular immunophenotyping has become a new discipline in diagnostic haematology and immunology, and is invaluable in the rapid diagnosis of leukaemia and monitoring disease progression in human immunodeficiency virus infected individuals. The introduction of bench top flow cytometers has meant that immunophenotyping is now also used for the quantitation of CD34(+) peripheral blood stem cells (PBSCs) to ensure the correct timing and adequacy of haematopoietic progenitor cell harvests. Furthermore, flow cytometry has become an important tool for the counting of leucocytes in blood components after leucocyte depletion. Because this new discipline is now such a major diagnostic and prognostic tool in the clinical arena, its use must be subject to both internal and external quality control. Such a requirement was first recognised as early as 1986 when an Inter-Regional Quality Assessment Scheme (IRQAS) was initiated for laboratories that undertook the immunocytochemical diagnosis of leukaemia using the alkaline phosphates anti-alkaline phosphatase technique. This programme began with around 25 UK laboratories. In 1990, after the introduction of two more programmes (one for leukaemia diagnosis using UV microscopy and latterly flow cytometry, and one for the enumeration of CD4(+) T cells) the IRQAS achieved UK National External Quality Assessment Scheme (UK NEQAS) status and changed its title to UK NEQAS for Leucocyte Immunophenotyping. In the past decade the once small IRQAS programme has evolved into the largest international scheme of its kind, providing EQA to over 650 laboratories world wide for leukaemia immunophenotyping, lymphocyte subset analysis, PBSCs, and more recently low level leucocyte counting. Over the years, this EQA programme has highlighted important problems, such as the inappropriate use of fluorochromes and antibody titre, and the identification of effective gating strategies, all of which have contributed directly to the high interlaboratory variations seen in cellular immunophenotyping. Furthermore, particularly in absolute counting of lymphocyte subsets, PBSCs, and the enumeration of low numbers of leucocytes, UK NEQAS for Leucocyte Immunophenotyping programmes have been instrumental in highlighting the differences that occur between single and dual platform flow cytometric technologies. As a result of these findings, UK NEQAS for Leucocyte Immunophenotyping has helped to reduce the variation seen on an interlaboratory basis and enabled greater standardisation both in the UK and internationally. These advances have been attributable to the development, by UK NEQAS for Leucocyte Immunophenotyping, of a unique whole blood stabilising process that ensures the retention of the physical characteristics (both light scatter and antigenic profile) required of cells to ensure successful cellular immunophenotyping. This major technological advancement has enabled the distribution of specimens for EQA purposes on a global scale that have minimal matrix effect and behave in a manner identical to fresh blood for several months after stabilisation.

Identification of novel FLT-3 Asp835 mutations in adult acute myeloid leukaemia

Genomic DNA from 97 cases of adult de novo acute myeloid leukaemia (AML) was screened using polymerase chain reaction (PCR) and conformation-sensitive gel electrophoresis (CSGE) for FLT3 exon 20 mutations. Initial sequencing of four cases, representing the spectrum of CSGE abnormalities, revealed changes affecting codon Asp835 in three cases and also an intron 20 A to G change. In order to identify all possible Asp835 alterations, as well as the frequency of the intronic change nucleotide 2541 + 57 A-->G, the patient PCR products were digested with EcoRV and NlaIII respectively. Seven cases (7.2%) possessed a mutation affecting Asp835; these were identified, following DNA sequencing, as Asp835Tyr (n = 5), Asp835His (n = 1) and Asp835del (n = 1). Alterations affecting Asp835 were not found in 80 normal control DNA samples. In contrast, the nucleotide 2541 + 57 A-->G change was shown to be a polymorphism, with an allelic frequency of 0.24 for the G and 0.76 for the A allele. This study reports, for the first time, point mutations in the human FLT3 gene that, because of their homology with other class III receptor tyrosine kinase mutations, probably result in constitutive activation of the receptor.

Interferon alpha and zidovudine therapy in adult T-cell leukaemia lymphoma: response and outcome in 15 patients

Adult T-cell leukaemia lymphoma (ATLL) is an aggressive disease caused by the human T-lymphotropic virus 1 (HTLV-I) with a short survival. Responses to interferon alpha (IFN-alpha) and zidovudine (AZT) have been documented but not with long-term follow-up. We treated 15 ATLL patients with IFN and AZT. Eleven patients had acute ATLL, two had lymphoma and two smouldering ATLL, with progression. The main features were: organomegaly (14), skin lesions (10), high white blood cell (WBC) count (11) and hypercalcaemia (9). Eleven patients had previously received chemotherapy and one had received an autograft. At the time of the study, seven patients had progressive disease and eight were in partial or complete clinical remission. Responses (PR) lasting 2+ to 44+ months were seen in 67%; 26% did not respond (NR) and one patient was not evaluable. Hypercalcaemia predicted a poor outcome but differences were not significant. Eight of the 15 patients have died 3-41 months from diagnosis. Median survival for the 15 patients was 18 months. Survival of the NR ranged from 4 to 20 months; six PR patients are alive 8-82 months from diagnosis. The differences in survival between NR (median: 6 months) and PR (55% of patients alive at 4 years) were statistically significant (P = 0.002). In conclusion, IFN and AZT improves the outcome of ATLL patients and helps maintain responses.

Fluorescence in situ hybridization analysis of 25 cases of idiopathic myelofibrosis and two cases of secondary myelofibrosis: monoallelic loss of RB1, D13S319 and D13S25 loci associated with cytogenetic deletion and translocation involving 13q14

To identify a commonly deleted region of 13q14 in idiopathic myelofibrosis (IMF), we used fluorescence in situ hybridization analysis to test for deletion of the RB1 and BRCA2 genes, and the microsatellite loci D13S319 and D13S25, in a series of 25 patients. A further two patients with myelofibrosis secondary to polycythaemia vera and essential thrombocythaemia with reciprocal 13q translocations were studied in an attempt to further define the CDR. Twenty out of 21 patients with a cytogenetically normal chromosome 13 failed to show allelic loss with any of the four probes. In contrast, all four cases with cytogenetic deletion of 13q14 and both cases with 13q translocations involving 13q14 exhibited loss of RB1, D13S319 and D13S25. Loss of the BRCA2 locus was present in a single case only. Our results indicate that cryptic deletions of the 13q14 in myelofibrosis are rare. In addition, the genetic loss associated with cytogenetic 13q14 deletions or reciprocal translocations involving 13q14 is large and encompasses the gene-rich region around RB1, D13S319 and D13S25.

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.

Cytogenetically cryptic AML1-ETO and CBF beta-MYH11 gene rearrangements: incidence in 412 cases of acute myeloid leukaemia

The rearrangements t(8;21)(q22;22) and inv(16)(p13q22) are two of the most frequently seen in acute myeloid leukaemia (AML), accounting for 8% and 4% of cases respectively. Detection of these abnormalities is important for disease management as both are associated with good responses to conventional chemotherapy and prolonged disease-free survival. Recent reports using reverse transcriptase polymerase chain reaction (RT-PCR) suggest that significant proportions of AML cases without a visible t(8;21) or inv(16) show expression of an abnormal fusion gene transcript and, consequently, they could not be detected using conventional cytogenetic analysis alone. We present here a four centre study involving 412 cases of AML screened using both standard cytogenetics and RT-PCR for AML1-ETO and CBF beta-MYH11. We detected a cytogenetic t(8;21) in 31 out of 412 (7.5%) cases and an inv(16) or t(16;16) variant in 27 out of 412 (6.6%) cases. RT-PCR detected only two cases (0.5%) of cryptic t(8;21) and no instances of cryptic inv(16). Both cryptic t(8;21) cases had the classic M2 FAB morphology for this type of disease. Our data concur with the established FAB type distribution of the rearrangements and indicate that cryptic t(8;21) and inv(16) may be much less frequent than reported elsewhere.

Are aberrant BCR--ABL transcripts more common than previously thought?

We report the use of multiplex polymerase chain reaction (PCR), using 4% polyacrylamide gel electrophoresis (PAGE) for the detection of BCR-ABL transcripts in Philadelphia-positive disease. Three out of 50 cases [two out of 37 chronic myeloid leukaemia (CML), one out of 13 acute lymphoblastic leukaemia (ALL)] possessed rare breakpoints; an e19a2 and e13a3 in CML and an e1a3 in the ALL. We suggest that multiplex PCR using 4% PAGE and optimized for smaller transcript detection may lead to a higher detection rate of rare BCR-ABL breakpoints. Multiplex PCR, however, failed to distinguish e13a2 from e1a3 transcripts. Finally, the presence of e13a3 in CML supports the view that abl exon 2 sequences are unnecessary for the pathogenesis of 'classic' CML.

FLT3 internal tandem duplication mutations in adult acute myeloid leukaemia define a high-risk group

Genomic DNA from 106 cases of adult de novo acute myeloid leukaemia (AML) was screened by polymerase chain reaction (PCR) and gel electrophoresis for FLT3 internal tandem duplication (ITD) mutations within the juxtamembrane (JM) domain. FLT3 mutations were detected in 14 cases (13.2%) and occurred in FAB types M1 (4 out of 14 cases), M3 (1 out of 10 cases), M4 (5 out of 37 cases) and M5 (4 out of 11 cases). Sequence analysis of four cases with abnormal PCR electrophoretic patterns revealed in frame duplications in the region of exon 11 of between 27 and 111 base pairs. Three are predicted to result in the tandem duplication of adjacent amino acid residues and one to result in a tandem duplication plus insertion of a novel amino acid motif. Statistical analysis showed the FLT3 mutations to be a strong prognostic factor, with patients lacking the mutation surviving significantly longer from diagnosis (mean 29.1 months) than those with an ITD (mean 12.8 months; P = 0.0002). Thirteen of the 14 patients with FLT3 mutations died within 18 months of diagnosis. FLT3 mutations were of prognostic significance in good risk disease (P = 0.04), as well as in patients with standard risk disease (P = 0.0096). This study demonstrates that the FLT3 ITD mutation occurs in a significant percentage of adult AML cases and is an important adverse prognostic factor that appears independent of conventional karyotypic findings.

Autoimmune thrombocytopenia: a complication of fludarabine therapy in lymphoproliferative disorders

We describe two cases of autoimmune thrombocytopenia precipitated by fludarabine therapy in patients with chronic lymphatic leukaemia. Both were treated with high dose steroids and initially responded with recovery of normal platelet counts. One patient developed recurrent autoimmune thrombocytopenia on two occasions following re-exposure to the drug when his disease had become refractory to all other treatments. A retrospective review of the case notes of 45 patients with lymphoproliferative disorders treated with fludarabine over the past 6 years indicated the development of autoimmune thrombocytopenia in 4.5% (two out of 45) and autoimmune haemolytic anaemia in 6.7% (three of the 45).

Scrotal ulceration during all-trans retinoic (ATRA) therapy for acute promyelocytic leukaemia

We report the development of painful scrotal ulceration in two patients during treatment with all-trans-retinoic acid (ATRA) for acute promyelocytic leukaemia (APL). ATRA 45 mg/m2 was administered orally for 8 days prior to the addition of standard induction chemotherapy. Painful scrotal ulceration developed in both cases within 2 weeks of therapy (9 and 13 days) and responded slowly to drug withdrawal and systemic, or topical, corticosteroids. A total of 17 APL patients have been treated with ATRA at our institution during the last 10 years, giving an incidence of approximately 12%. The present report, together with a review of literature, suggests that scrotal ulceration is a specific adverse effect of ATRA therapy and that this complication may be more common than previously documented.

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.

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 </= 5% in 39% of the laboratories (trial 1), increasing to 65% by trial 3. Interlaboratory variation was reduced from 23.3% (trial 1) to 10.8% in trial 3. In trial 2, 70% of laboratories achieved an intralaboratory CV </= 5% using TruCount, increasing to 74% for trial 3; the interlaboratory CV was reduced from 23.4% to 9.5%. Comparative analysis of the EWGCCA and the UK NEQAS cohorts revealed that EWGCCA laboratories, using the standardized approach, had lower interlaboratory variation. Thus, the use of a common standardized protocol and targeted training significantly reduced intra- and interlaboratory CD34+ cell count variation.

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.

Pathogenesis and management of idiopathic myelofibrosis

Idiopathic myelofibrosis is the least common and carries the worst prognosis of the chronic myeloproliferative disorders. The primary disease process is a clonal haematopoietic stem cell disorder which results in a chronic myeloproliferation and an atypical megakaryocyte hyperplasia. In contrast, the characteristic stromal proliferation is a reactive phenomenon, resulting from the inappropriate release of megakaryocyte/platelet-derived growth factors, including PDGF, TGF-beta bFGF and calmodulin. The median survival is approximately 4 years, although individual survival varies greatly. A variety of prognostic schema have been developed which enable the identification of high-risk patients, for whom bone marrow transplantation should be considered. Management for the majority of patients, however, is directed towards the alleviation of symptoms and improvement in quality of life. This review summarizes the recent advances in our understanding of the disease's pathogenesis and discusses the limited therapeutic options available to clinicians.

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.

Efficacy of urate oxidase (uricozyme) in tumour lysis induced urate nephropathy

Urate oxidase (uricozyme) is an enzyme of non-human origin capable of oxidizing human uric acid to allantoin, a highly soluble product at renal tubule pH. We report its efficacy in three patients with acute urate nephropathy due to tumour lysis in chronic lymphatic leukaemia and high grade lymphoma. Two patients had an additional obstructive nephropathy due to ureteric urate crystals. An intravenous infusion (100 units/kg in 50 ml saline over 30 min) was given for between two and five consecutive days. All patients showed a rapid fall in serum urate levels with associated diuresis, correction of metabolic disturbance and full resolution of uraemia within a week. The treatment was well tolerated and caused a rapid resolution of clinical symptoms in all cases. We review the literature relating to the use of this agent both in the treatment of hyperuricaemic acute renal failure and gouty arthritis.

Idiopathic myelofibrosis: pathogenesis, natural history and management

Idiopathic myelofibrosis is a chronic myeloproliferative disorder characterized by bone marrow fibrosis, extramedullary haematopoiesis and a leucoerythroblastic blood picture. The marrow fibrosis results from an increased deposition of various interstitial and basement membrane glycoproteins, including collagen types I, III, IV, V and VI, fibronectin, vitronectin, laminin and tenascin. In addition, a marked neovascularization is present, even in the early proliferative phase of the disease. In contrast to the clonal haematopoiesis, the increased bone marrow stromal tissue is thought to be a reactive phenomenon, resulting from the inappropriate release of megakaryocyte/platelet-derived growth factors, including PDGF, TGF-beta, EGF, bFGF and calmodulin. Recent cytogenetic studies have highlighted three defects, namely del(13q), del(20q) and partial trisomy 1q, that account for nearly 70% of all abnormalities at diagnosis, and suggests that in many patients gene loss and/or inactivation may be an important pathogenetic mechanism. The median survival is approximately 4 years, although individual survival varies greatly. Prognostic schema enable the identification of patients with a limited life expectancy, for whom bone marrow transplantation should be considered. However, for the majority of patients therapy is supportive and consists of blood transfusions, androgens to sustain erythropoiesis, cytoreductive agents to prevent thrombocythaemia and, in carefully selected cases, splenectomy. The role for a number of experimental therapies, such as vitamin D3 analogues, alpha and gamma interferons and erythropoietin has yet to be defined.

Cytogenetic abnormalities and their prognostic significance in idiopathic myelofibrosis: a study of 106 cases

The prognostic significance of cytogenetic abnormalities was determined in 106 patients with well-characterized idiopathic myelofibrosis who were successfully karyotyped at diagnosis. 35% of the cases exhibited a clonal abnormality (37/106), whereas 65% (69/106) had a normal karyotype. Three characteristic defects, namely del(13q) (nine cases), del(20q) (eight cases) and partial trisomy 1q (seven cases), were present in 64.8% (24/37) of patients with clonal abnormalities. Kaplan-Meier plots and log rank analysis demonstrated an abnormal karyotype to be an adverse prognostic variable (P<0.001). Of the eight additional clinical and haematological parameters recorded at diagnosis, age (P<0.01), anaemia (haemoglobin < or = 10 g/dl: P<0.001), platelet (< or = 100 x 10(9)/l, P<0.0001) and leucocyte count (> 10.3 x 10(9)/l; P=0.06) were also associated with a shorter survival. In contrast, sex, spleen and liver size, and percentage blast cells were not found to be significant. Multivariate analysis, using Cox's regression, revealed karyotype, haemoglobin concentration, platelet and leucocyte counts to retain their unfavourable prognostic significance. A simple and useful schema for predicting survival in idiopathic myelofibrosis has been produced by combining age, haemoglobin concentration and karyotype with median survival times varying from 180 months (good-risk group) to 16 months (poor-risk group).

The Rhnull phenotype in an English individual: haematological, serological and immunological studies

We have characterized the first case of Rhnull phenotype to be identified in England. The red cells were serologically negative for C, c, Cw, D, E, e, f, hr B, Rh17, Lw a, Lw ab and Duclos, while the patient's serum contained anti-Rh29, which was subsequently boosted by transfusion. The Rh phenotype of the patient's son (R1r) confirmed that this was a regulator type of Rhnull in the patient. Follow up studies confirmed the presence of a mild chronic anaemia with stomatocytes and spherocytes; electron microscopy revealed the presence of cells with deep central indentations. Osmotic fragility was increased to a level intermediate between normal and hereditary spherocytic controls. The presence of ongoing haemolysis was indicated by a mild reticulocytosis and splenomegaly. The potent anti-Rh29 has made the provision of compatible blood difficult and autologous units have been frozen. The case illustrates the rare phenomenon of the Rhnull phenotype which not only causes problems for the transfusionist but should also be recognized as a cause of haemolytic anaemia secondary to a membrane defect. Blood film and Rh phenotyping are useful preliminary investigations in suspected cases.