Cytometer developed to provide breakthrough CD4 monitoring test
HIV/AIDS Professor Debbie Glencross is the South African haematologist who found a cheaper, more accurate method of checking the CD4 cell counts of patients with HIV/AIDS.
It is not just the simplicity of her idea that makes this so appealing to clinicians. It is the difference it makes to some of the poorest and vulnerable people in South Africa. By saving millions of dollars in monitoring costs, it allows governments in Africa offer a more comprehensive AIDS treatment program.
More than 70% of the 25.8 million people living with HIV live in sub-Saharan Africa—including 88% of the world’s HIV-positive children. In 2014, an estimated 1.4 million people in the region became newly infected. An estimated 790,000 adults and children died of AIDS, accounting for 66% of the world’s AIDS deaths in 2014.
Prof Glencross is Director and Principle Pathologist in the Flow Cytometry unit of the Department of Haematology at the Charlotte Maxeke Johannesburg Academic Hospital, South Africa.
Her breakthrough PLG (Pan-Leukocyte Gating) method simplifies conventional flow cytometry techniques for CD4 monitoring. It is easy to quality control and requires no specialist training.
“I always think there has to be a simpler, easier way of doing things,” she explained.
The evidence confirming Prof Glencross’s PLG test was published in the internationally regarded peer review journal, Cytometry, to great acclaim, including from the World Health Organization (WHO).The South African National Health Laboratory Service (NHLS) has now patented Prof Glencross’s test so that it can remain easily accessible in those countries most affected by AIDS.
“It gratifying knowing we have done something that can have such an impact,” she added.
Aquios enables nearer patient CD4 monitoring
Beckman Coulter’s CARES initiative (Cellular Accessible Retroviral Evaluation Systems) in Africa started in 2004 with Glencross's breakthrough. Beckman Coulter has now taken this a step further by addressing the increasing demand in Africa for nearer patient CD4 monitoring. It also addresses the one limitation of Prof Glencross’s original PLG test which, at the time it was invented, still had to rely on conventionally-sized, larger-flow cytometry instruments to carry it out; not ideal for resource-poor, rural settings.
As Prof Glencross explained: “Our objective is to empower smaller community laboratories so that they can extend the availability of PLG* to meet demand while still meeting the testing standards required by the National Health Laboratory Service. This will enable best clinical and laboratory practice while reducing the time it takes to deliver the result.”
"...used in smaller, more rural locations by less qualified people."
Beckman Coulter has used its global expertise in flow cytometry to develop a compact flow cytometry analyser, the AQUIOS CL Flow Cytometer. This also addresses the needs of the NHLS to give smaller, rural labs the resources to carry out these tests nearer to the patient. At the same time, it is still within the laboratory environment, adhering to the protocols for standardization and quality control required by the NHLS. The cost of anti-retroviral drugs is extremely expensive. But the drugs are pointless without being able to monitor the CD4 count. Due to the robustness of the Aquios PLG test, samples can now be analyzed up to five days after collection without compromising the quality.
The high precision ‘LOAD & GO’ Aquios can be used in smaller, more rural locations by less qualified people. Previously, blood samples had to travel for several days to reach the larger, flow cytometry centres. Dr. Jeannine T. Holden, Beckman Coulter’s Director of Scientific Affairs, pointed out: “A compact laboratory instrument is now available that offers high quality, fully automated CD4 counts in the near-patient setting. The rapid turnaround time and ease of use enables doctors and patients can get results in well under an hour, so that timely treatment decisions can be made.”
Simplifying flow cytometry technique
The basis of the body's immune system is a set of several different types of white blood cells, including CD4 cells, which work together to ward off infection.
Clinicians can monitor the immunity of HIV patients by counting the number in a patient’s blood. CD4 cells are destroyed by the virus with a declining number indicating how far the disease has progressed. They can also measure how well a patient is reacting to antiretroviral drugs by carrying out CD4 tests. In South Africa, a person’s CD4 cell count must be down to 200 ml or 500 cells or less to qualify for antiretroviral treatment through the country’s national program.
"She realised that using the white cell count as a stable reference point would eliminate the need for additional quality control steps."
Prof’s PLG test provides an alternative way of monitoring carrying out the CD4 count. Large labs differentiate between the different types of white blood cells, count them and then work out, mathematically, the number of CD4 cells in each millionth of a litre of blood. While this is an accurate method, it can be laborious and Glencross's idea was to simplify it.
She experimented with just measuring all the white blood cells and using the results in the mathematical equation. This meant her method dispensed with the time-consuming and costly isolation of 9-12 antibodies recommended for quality control in any lymphocyte referenced testing. She realised that using the white cell count as a stable reference point would eliminate the need for additional quality control steps, while still maintaining standards.
“Changing the reference point to total white blood cells in the dual platform (DP) system dramatically improved quality control,” she explained. “One of the reasons I came up with the idea in the first place was out of desperation over quality control.”
PLG reduces TAT by 400% in community labs
The PLG test is a much simpler flow cytometry method which delivers a CD4 count without sacrificing quality or stability. It can be implemented by staff with rudimentary laboratory skills.
On the Aquios, it uses a 2-color, pre-optimised reagent and provides both CD4% and absolute counts. With good correlation with ‘Gold Standard’ flow cytometry, its robustness is particularly important in countries that cannot afford the ‘gold standard’ CD4 testing. Independent studies have confirmed that results between the two methods are comparable 99% of the time.
“The PLG test simplifies flow cytometry so that it can be carried out in these smaller labs nearer the patient."
A recent study carried out by Prof. Glencross on behalf of the NHLS has shown that implementing a community-based CD4 lab testing programme in rural South Africa would both improve turnaround times (TAT) and save costs. The initial findings were presented at the 2014 African Society of Laboratory Medicine’s first annual international conference.
It highlighted the benefits of maintaining CD4 testing within the laboratory service, albeit carried out nearer the patient by community (third-tier) labs. Prof Glencross reported that more than a quarter more CD4 tests were carried out (27%) while TAT was reduced from 12-38 hours to 4-13 hours, down approximately 400%.
And she concluded: “The cost of our HIV/AIDS burden makes it essential that we find new and more cost effective ways of providing CD4 monitoring. In South Africa, the role of the community lab has a growing part to play as a satellite service to the central labs.
“The PLG test simplifies flow cytometry so that it can be carried out in these smaller labs nearer the patient. This reduces the turnaround time so that people can have their results more quickly- but without increasing costs.”
*Appropriate for L4 central, L3 regional, L2 district laboratories and some well-developed L1 primary sites and results should be reviewed by a qualified flow cytometrist.
Results should be reviewed by a qualified flow cytometrist.
PLG is CE marked. PLG is available for sale in specific countries. It is not available for sale in US or Canada.
Article and interview with Prof Debbie Glencross as part of Aquios PLG FLOWCARES Campaign