A compact time-of-flight mass spectrometer for ion source characterization.

A compact time-of-flight mass spectrometer with overall dimension of about 413 × 250 × 414 mm based on orthogonal injection and angle reflection has been developed for ion source characterization. Configuration and principle of the time-of-flight mass spectrometer are introduced in this paper. The mass resolution is optimized to be about 1690 (FWHM), and the ion energy detection range is tested to be between about 3 and 163 eV with the help of electron impact ion source. High mass resolution and compact configuration make this spectrometer useful to provide a valuable diagnostic for ion spectra fundamental research and study the mass to charge composition of plasma with wide range of parameters.

CD4 lymphocyte enumeration in patients with human immunodeficiency virus infection using three-colour and four-colour dual-platform flow cytometry: an inter-laboratory comparative evaluation.

INTRODUCTION: This study aims to evaluate the correlation and agreement between 2 methodologies of CD4 lymphocyte enumeration. MATERIALS AND METHODS: Fifty-two blood samples from patients with human immunodeficiency virus (HIV) infection were sent for CD4 lymphocyte enumeration at 2 major hospitals using dual-platform flow cytometry where the absolute lymphocyte counts were determined on separate haematology analyzers. CD4 cell enumeration was accomplished using 3-colour flow cytometry on the FACSCalibur cytometer (Becton Dickinson) in Hospital A and 4-colour flow cytometry on the Coulter Epic XL cytometer (Beckman Coulter) in Hospital B. The percentages and absolute counts of CD4 lymphocytes obtained were analysed using both linear regression and Bland-Altman plots. RESULTS: On linear regression plots, the total white cell counts, absolute lymphocyte counts, CD4 lymphocyte percentages and absolute CD4 counts from the 2 hospitals correlated well with correlation coefficients, r > 0.95. On the Bland-Altman plots, there was a mean difference of 0.13 x 10(9)/L and 0.06 x 10(9)/L in the total white cell and absolute lymphocyte counts from the 2 hospitals respectively. The CD4 lymphocyte percentages revealed a mean difference of only 0.05% (95% limits of agreement, -3.6 to 3.7%) but there was a mean difference of 14/uL in the absolute CD4 lymphocyte counts (95% limits of agreement, -113 to 142/uL). CONCLUSIONS: The CD4 lymphocyte percentages obtained using the 3-colour and 4-colour flow cytometry correlated and agreed well. However, the absolute CD4 lymphocyte counts obtained using the dual-platform technique in both the hospitals did not agree well. Hence, absolute CD4 lymphocyte counts from the 2 hospitals cannot be used interchangeably in clinical practice due to poor inter-laboratory comparability.

ESA developments in life support technology: achievements and future priorities.

Following an enthusiastic start in 1985, ESA's life support technology development programme was re-assessed in the mid- to late-1990s to reflect the strong reduction in European manned space ambitions which occurred at that time. Further development was essentially restricted to activities that could constitute ISS upgrades or enhancements, or support ISS utilisation/operations, together with a single, limited, activity (MELISSA) aimed at bioregenerative life support, in the continuing hope that there might be "life after Station". The paper describes the current status of these activities and summarises the main priorities for future development that were identified at the April 1999 Workshop on Advanced Life Support.

The monitoring of gaseous contaminants in spacecraft cabin atmospheres.

The accumulation of toxic or otherwise harmful trace gases in a spacecraft cabin is a very serious concern in terms of the health and safety of the crew. Although methods exist for controlling the evolution of such contaminants, techniques for monitoring the success of these methods, on board and in near- real-time, are still under development. One such technique, based on the use of FTIR interferometry, is being developed in Europe. A prototype instrument has been assembled, making extensive use of 'off-the-shelf' hardware and software, and tested for its ability to detect and quantify--within a maximum period of 1 minute and in the presence of water vapour and carbon dioxide 21 of the most frequently detected contaminants on past Shuttle and Spacelab flights. Results have confirmed that such contaminants can be detected and measured with an acceptable degree of precision.

Evaluation of high performance liquid chromatography for routine estimation of haemoglobins A2 and F.

AIMS: To compare high performance liquid chromatography (HPLC) with conventional methods for the estimation of blood haemoglobin A2 (HbA2) and haemoglobin F (HbF) concentrations in routine thalassemia screening. METHODS: An HPLC system (the VARIANT Hemoglobin Testing System) was tested for precision and reproducibility in the measurement of HbA2 and HbF, and reference ranges were obtained for a local healthy adult population. HPLC was compared with column anion exchange chromatography for HbA2 measurement, and radial immunodiffusion, or alkaline denaturation for HbF measurement. The reliability of HbA2 measurement by HPLC for the detection of beta thalassaemia and HbE was assessed in 200 consecutive samples for routine thalassaemia screening. RESULTS: HPLC was rapid, technically easy, and gave good precision and reproducibility. In all comparisons linear regression analysis showed good correlation between HbA2 or HbF concentrations determined by HPLC and by the respective conventional methods. All beta thalassaemia or haemoglobin E carriers presumptively identified by conventional methods in 200 consecutive samples were detected by HbA2 measurement using HPLC, without any false positive or false negative results. CONCLUSIONS: The measurement of HbA2 and HbF by HPLC is rapid, reproducible, and precise. It is as reliable as column chromatography for the measurement of HbA2 and radial immunodiffusion or alkaline denaturation for the measurement of HbF. HPLC may be an appropriate method for rapid screening in population surveys for beta thalassaemia and HbE carriers.

Referral of patients to an anticoagulant clinic: implications for better management.

The quality of anticoagulant treatment of ambulatory patients is affected by the content of referral letters and administrative processes. To assess these influences a method was developed to audit against the hospital standard the referral of patients to one hospital anticoagulant clinic in a prospective study of all (80) new patients referred to the clinic over eight months. Administrative information was provided by the clinic coordinator, and the referral letters were audited by the researchers. Referral letters were not received by the clinic for 10% (8/80) of patients. Among the 72 referral letters received, indication for anticoagulation and anticipated duration of treatment were specified in most (99%, 71 and 81%, 58 respectively), but only 3% (two) to 46% (33) reported other important clinical information (objective investigations, date of starting anticoagulation, current anticoagulant dose, date and result of latest international normalised ratio, whether it should be the anticoagulant clinic that was eventually to stop anticoagulation, patients' other medical problems and concurrent treatment. Twenty two per cent (16/80) of new attenders were unexpected at the anticoagulant clinic. Most patients' case notes were obtained for the appointment (61%, 47/77 beforehand and 30% 23/77 on the day), but case notes were not obtained for 9% (7/77). The authors conclude that health professionals should better appreciate the administrative and organisational influences that affect team work and quality of care. Compliance with a well documented protocol remained below the acceptable standard. The quality of the referral process may be improved by using a more comprehensive and helpful referral form, which has been drawn up, and by educating referring doctors. Measures to increase the efficiency of the administrative process include telephoning the clinic coordinator directly, direct referrals through a computerised referral system, and telephone reminders by haematology office staff to ward staff to ensure availability of the hospital notes. The effect of these changes will be assessed in a repeat audit.

Erythropoietin levels and inhibition of erythropoiesis in end-stage renal failure.

Anaemia of chronic renal failure is multifactorial. Twenty-one patients with end-stage renal disease (ESRD) and 21 normal subjects were studied to determine the significance of serum erythropoietin levels and erythropoiesis inhibition in the aetiology of renal anaemia. Serum erythropoietin levels and erythropoiesis inhibition were measured by determining the incorporation of labelled-thymidine into the DNA of rabbit bone marrow cells. The mean haemoglobin concentration was 9.0 +/- 0.5 g/dl (mean +/- SEM) in ESRD and 14.4 +/- 0.4 g/dl in normal controls. Serum erythropoietin levels (99.9 +/- 17.9 mU/ml in ESRD vs 74.9 +/- 9.7 mU/ml in normal controls) and inhibition of erythropoiesis (252 +/- 28.9 in ESRD vs 186.2 +/- 19.4 in normal controls) were not significantly different in both groups. However, erythropoiesis inhibition had a significant correlation with the degree of anaemia (p less than 0.01). The results suggest that erythropoiesis inhibition play a significant role in the pathogenesis of renal anaemia.

Immunophenotypic characterisation of monocytoid differentiation markers in acute non-lymphoblastic leukaemias.

The FAB classification of acute non-lymphoblastic leukaemias has been shown to have some clinical use in the prognostication of patient survival. ANLL with monocytoid features (M4, M5) fare worse than those which are predominantly myeloblastic (M1, M2). Classification is, however, sometimes difficult if non-specific esterase activity is not strongly expressed. Monoclonal antibody characterisation of myeloid differentiation antigens may be of some use as a supplementary aid. We immunophenotyped the blast cells from 26 cases for HLA-Dr, CD14 (Mo2, My4), CD13 (My17) and CD33 (My9) expression using the APAAP method. A combination of CD14 and CD33 used together was useful in differentiating myeloblastic from monocytoid acute non-lymphoblastic leukaemias. We conclude that the use of surface markers is a useful adjunct to the diagnostic means presently available.