Biomedical subjects

Francis Mandy

Publications and source records attributed to Francis Mandy.

6 recordsLinked to original sources

PubMed2006

Multiplexed and microparticle-based analyses: quantitative tools for the large-scale analysis of biological systems.

While the term flow cytometry refers to the measurement of cells, the approach of making sensitive multiparameter optical measurements in a flowing sample stream is a very general analytical approach. The past few years have seen an explosion in the application of flow cytometry technology for molecular analysis and measurements using microparticles as solid supports. While microsphere-based molecular analyses using flow cytometry date back three decades, the need for highly parallel quantitative molecular measurements that has arisen from various genomic and proteomic advances has driven the development in particle encoding technology to enable highly multiplexed assays. Multiplexed particle-based immunoassays are now common place, and new assays to study genes, protein function, and molecular assembly. Numerous efforts are underway to extend the multiplexing capabilities of microparticle-based assays through new approaches to particle encoding and analyte reporting. The impact of these developments will be seen in the basic research and clinical laboratories, as well as in drug development.

Coloring Agents↗

PubMed2002

Impact of the international program for Quality Assessment and Standardization for Immunological Measures Relevant to HIV/AIDS: QASI.

Measurements of CD4 T-cell levels are essential for the assessment of human immunodeficiency virus (HIV) disease course, clinical staging, epidemiological studies, and decisions regarding prophylactic therapies against opportunistic infection. Until now, only in the industrialized countries was T-cell subset monitoring considered a practical option to assess disease progression. The Quality Assessment and Standardization for Immunological Measures Relevant to HIV/AIDS (QASI) program was established in 1997 to meet performance assessment for immunophenotyping laboratories in countries where such service is not available. The QASI program is provided at no cost to any laboratory in a resource-poor setting that wishes to participate. This report describes the beneficial impact of participation in the QASI program. Carefully selected commercial stabilized whole blood preparations were sent regularly to participating laboratories. Participants reported the T-cell subset values they obtained by flow cytometry. Once the aggregate mean values for the T-cell subsets were established for the shipment, a comprehensive and confidential report was sent to each laboratory. The results from five consecutive shipments were analyzed. The coefficient of variation decreased from 7.2% to 4.7% and from 14.2% to 8.8% for percent and absolute CD4 T-cell counts, respectively. With the implementation of the QASI program using commercial stabilized whole blood specimens, it is possible to reduce interlaboratory error. This study illustrates that a quality assessment program can improve the overall performance of laboratories. Reducing interlaboratory variation can enhance significantly the effectiveness of multicenter HIV vaccine or drug trial evaluation.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Evaluation of a universal template for single-platform absolute T-lymphocyte subset enumeration.

The single-platform absolute T-lymphocyte subset analysis was evaluated utilizing a universal protocol in a Canadian multicenter study with the collaboration of the members of the Canadian HIV Trials Network (CTN). Participants used flow cytometers and reagents of their choice for labeling and lysing whole blood. Over a 2-year period, CTN laboratories performed single-platform absolute T-lymphocyte subset enumerations on fresh and commercial stabilized blood products using commercially available microfluorospheres TruCount and Flow-Count. This multicenter evaluation demonstrated that the application of a universal template for single-platform analysis provides a generic approach that embraces a wide array of immunophenotyping settings available in clinical laboratory.

CD3 Complex↗

PubMed2002

Evaluation of stabilized blood cell products as candidate preparations for quality assessment programs for CD4 T-cell counting.

BACKGROUND: Exceptionally robust cell preparations are needed for quality assessment programs (QAPs) such as the International Program for Quality Assessment and Standardization for Immunological Measures (QASI) relevant to HIV/AIDS. A suitable product must withstand environmental stress related to transportation for a minimum of 6 days. The two objectives of this study are (1) to evaluate the performance of various commercial preparations with multicenter participation and (2) to evaluate the robustness of stabilized blood cell products. METHODS: Phase 1: The performance of stabilized blood cell products was evaluated in a multicenter QAP utilizing various staining procedures and flow cytometers. Absolute cell enumeration was achieved using single-platform T-cell subset methodology. Phase 2: The robustness of stabilized blood cell products was evaluated by monitoring T-cell subset values from samples stored at 4 degrees C, 22 degrees C, and 37 degrees C for up to 10 days. RESULTS: The largest interlaboratory variation in both absolute and relative T-cell values was 16% in samples with CD4 levels > or =400 cells per microliter and 21% in samples with CD4 levels <400 cells per microliter. Six preparations retained their phenotypic expression for 7 days at 4 degrees C and 22 degrees C. However, only two preparations remained stable for 4 days at 37 degrees C. CONCLUSION: Some stabilized cell preparations are more robust and therefore more suitable for quality assessment purposes.

CD3 Complex↗

PubMed2002

T-cell subset counting and the fight against AIDS: reflections over a 20-year struggle.

The story of T-lymphocyte subset immunophenotyping technology is reviewed on the occasion of the 20th anniversary of CD4 T-cell enumeration. Over time, immunophenotyping has evolved into precise, reliable, but complicated and expensive technology requiring fresh blood samples. The gating technologies that were universally adapted for clinical flow cytometry for the past decade relied on rapidly deteriorating morphological scatter characteristics of leukocytes. This special issue dedicated to CD4 T-cell enumeration features most of the available new options that will have a significant impact on how this technology will be implemented within the first decade of the 21st century. In a series of original publications, including the new NIH guideline for T-cell subset enumeration, contemporary gating protocols that use immunologically logical parameters are presented as part of the more reliable and affordable immunophenotyping alternative. Some of the improvements addressed here include the costs of the assays and the capacity to monitor interlaboratory and intralaboratory performances. It is clear that an effective attack on the human immunodeficiency virus (HIV) epidemic has to embrace resource-poor regions. Reducing the cost of the assay while improving reliability and durability is a move in the right direction.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Multiplexed immunoassays by flow cytometry for diagnosis and surveillance of infectious diseases in resource-poor settings.

An accurate, rapid and cost-effective diagnosis is the cornerstone of efficient clinical and epidemiological management of infections. Here we discuss the relevance of an emerging technology, multiplexed immunoassays read by flow cytometry, for the diagnosis of infectious diseases. In these assays, multiple fluorescent microspheres, conjugated to different antigens or antibodies, constitute the solid phase for detecting antibodies or antigens in biological samples. These assays seem to be more sensitive than traditional immunoassays, have a high throughput capacity, and provide a wide analytical dynamic range. Additionally, they have multiplexing ability-ie, they are capable of measuring multiple antibodies or antigens simultaneously. We discuss four different areas where this technology could make an impact in resource-poor settings: (i) infections causing rash and fever in children; (ii) sero-epidemiological studies on vaccine-preventable diseases; (iii) management of genital ulcers and vaginal discharge; and (iv) screening of infections in blood banking. We predict a widespread use for a new breed of small, affordable, practical flow cytometers as field instruments for replacing ELISA and RIA tests, which will also be capable of doing cellular immunological tests such as CD4+ T-cell enumeration and Plasmodium falciparum detection in whole blood.

Blood Banks↗