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11 December 2019 | Story Leonie Bolleurs
Aids read more

According to Global Statistics, there were approximately 37,9 million people across the globe with HIV/Aids in 2018. They also state that in 2018, an estimated 1,7 million individuals worldwide became newly infected with HIV. 

In the city of Masvingo, Zimbabwe, Claris Shoko is a Statistics lecturer at the Great Zimbabwe University. In her PhD thesis at the University of the Free State (UFS) in the Department of Mathematical Statistics and Actuarial Sciences, she presented the argument that the inclusion of both the CD4 cell count and the viral-load counts in the monitoring and management of HIV+ patients on antiretroviral therapy (ART), is helping in reducing mortality rates, leading to improved life expectancy for HIV/Aids patients. 

She received her doctoral degree at the December UFS Graduation Ceremonies, with her thesis: Continuous-time Markov modelling of the effects of treatment regimens on HIV/Aids immunology and virology. 

CD4 cell count and viral-load count

Dr Shoko explains: “When the human immunodeficiency virus (HIV) enters the human body, the virus attacks the CD4 cells in their blood. This process damages CD4 cells, causing the number of white blood cells in the body to drop, making it difficult to fight infections.”

“Clinical markers such as CD4 cell count and viral-load count (number of HIV particles in a ml of blood) provide information about the progression of HIV/Aids in infected individuals. These markers fully define the immunology and the virology of HIV-infected individuals, thereby giving us a clear picture of how HIV/Aids evolve within an individual.”

Dr Shoko continues: “The development of highly active antiretroviral therapy (HAART) has helped substantially to reduce the death rate from HIV. HAART reduces viral load-count levels, blocking replication of HIV particles in the blood, resulting in an increase of CD4 cell counts and the life expectancy of individuals infected with HIV. This has made CD4 cell counts and viral-load counts the fundamental laboratory markers that are regularly used for patient management, in addition to predicting HIV/Aids disease progression or treatment outcomes.”

In the treatment of HIV/Aids, medical practitioners prescribe combination therapy to attack the virus at different stages of its life cycle, and medication to treat the opportunistic infections that may occur. “The introduction of combined antiretroviral therapy (cART) has led to the dramatic reduction in morbidity and mortality at both individual level and population level,” states Dr Shoko.

Once HIV-positive patients are put on cART, the effectiveness of treatment is monitored after the first three months and a further follow-up is done every six months thereafter. During the monitoring stages, CD4 cell count and viral load is measured. Patients are also screened for any tuberculosis (TB) co-infection and checked for any signs of drug resistance. These variables determine whether or not there is a need for treatment change. 

She continues: “Previous studies on HIV modelling could not include both CD4 cell count and viral load in one model, because of the collinearity between the two variables. In this study, the principal component approach for the treatment of collinearity between variables is used. Both variables were then included in one model, resulting in a better prediction of mortality than when only one of the variables is used.”

“Viral-load monitoring helps in checking for any possibilities of virologic failure or viral rebound, which increases the rate of mortality if not managed properly. CD4 cell count then comes in to monitor the potential development of opportunistic infections such as TB. TB is extremely fatal, but once detected and treated, the survival of HIV/Aids patients is assured,” Dr Shoko explains.

Markov model

She applied the Markov model in her study. The model, named after the Russian mathematician Andrey Markov, represents a general category of stochastic processes, characterised by six basic attributes: states, stages, actions, rewards, transitions, and constraints. 

According to Dr Shoko, Markov models assume that a patient is always in one of a finite number of discrete states, called Markov states. All events are modelled as transitions from one state to another. Each state is assigned a utility, and the contribution of this utility to the overall prognosis depends on the length of time spent in each state. For example, for a patient who is HIV positive, these states could be HIV+ (CD4 cell count above 200 cells/mm3), Aids (CD4 cell count below 200 cells/mm3) and Dead.

“Markov models are ideal for use in HIV/Aids studies, because they estimate the rate of transition between multiple-disease states while allowing for the possible reversibility of some states,” says Dr Shoko, quoting Hubbard and Zhou.

“Relatively fewer HIV modelling studies include a detailed description of the dynamics of HIV viral load count during stages of HIV disease progression. This could be due to the unavailability of data on viral load, particularly from low- and middle-income countries that have historically relied on monitoring CD4 cell counts for patients on ART because of higher costs of viral load-count testing,” Dr Shoko concludes

News Archive

Heart diseases a time bomb in Africa, says UFS expert
2010-05-17

 Prof. Francis Smit

There are a lot of cardiac problems in Africa. Sub-Saharan Africa is home to the largest population of rheumatic heart disease patients in the world and therefore hosts the largest rheumatic heart valve population in the world. They are more than one million, compared to 33 000 in the whole of the industrialised world, says Prof. Francis Smit, Head of the Department of Cardiothoracic Surgery at the Faculty of Health Sciences at the University of the Free State (UFS).

He delivered an inaugural lecture on the topic Cardiothoracic Surgery: Complex simplicity, or simple complexity?

“We are also sitting on a time bomb of ischemic heart disease with the WHO (World Health Organisation) estimating that CAD (coronary artery disease) will become the number-one killer in our region by 2020. HIV/Aids is expected to go down to number 7.”

Very little is done about it. There is neither a clear nor coordinated programme to address this expected epidemic and CAD is regarded as an expensive disease, confined to Caucasians in the industrialised world. “We are ignoring alarming statistics about incidences of adult obesity, diabetes and endemic hypertension in our black population and a rising incidence of coronary artery interventions and incidents in our indigenous population,” Prof. Smit says.

Outside South Africa – with 44 units – very few units (about seven) perform low volumes of basic cardiac surgery. The South African units at all academic institutions are under severe threat and about 70% of cardiac procedures are performed in the private sector.

He says the main challenge in Africa has become sustainability, which needs to be addressed through education. Cardiothoracic surgery must become part of everyday surgery in Africa through alternative education programmes. That will make this specialty relevant at all levels of healthcare and it must be involved in resource allocation to medicine in general and cardiothoracic surgery specifically.

The African surgeon should make the maximum impact at the lowest possible cost to as many people in a society as possible. “Our training in fields like intensive care and insight into pulmonology, gastroenterology and cardiology give us the possibility of expanding our roles in African medicine. We must also remember that we are trained physicians as well.

“Should people die or suffer tremendously while we can train a group of surgical specialists or retraining general surgeons to expand our impact on cardiothoracic disease in Africa using available technology maybe more creatively? We have made great progress in establishing an African School for Cardiothoracic Surgery.”

Prof. Smit also highlighted the role of the annual Hannes Meyer National Registrar Symposium that culminated in having an eight-strong international panel sponsored by the ICC of EACTS to present a scientific course as well as advanced surgical techniques in conjunction with the Hannes Meyer Symposium in 2010.

Prof. Smit says South Africa is fast becoming the driving force in cardiothoracic surgery in Africa. South Africa is the only country that has the knowledge, technology and skills base to act as the springboard for the development of cardiothoracic surgery in Africa.

South Africa, however, is experiencing its own problems. Mortality has doubled in the years from 1997 to 2005 and half the population in the Free State dies between 40 to 44 years of age.

“If we do not need health professionals to determine the quality and quantity of service delivery to the population and do not want to involve them in this process, we can get rid of them, but then the political leaders making that decision must accept responsibility for the clinical outcomes and life expectancies of their fellow citizens.

“We surely cannot expect to impose the same medical legal principles on professionals working in unsafe hospitals and who have complained and made authorities aware of these conditions than upon those working in functional institutions. Either fixes the institutions or indemnifies medical personnel working in these conditions and defends the decision publicly.

“Why do I have to choose the three out of four patients that cannot have a lifesaving operation and will have to die on their own while the system pretends to deliver treatment to all?”

Prof. Smit says developing a service package with guidelines in the public domain will go a long way towards addressing this issue. It is also about time that we have to admit that things are simply not the same. Standards are deteriorating and training outcomes are or will be affected.

The people who make decisions that affect healthcare service delivery and outcomes, the quality of training platforms and research, in a word, the future of South African medicine, firstly need rules and boundaries. He also suggested that maybe the government should develop health policy in the public domain and then outsource healthcare delivery to people who can actually deliver including thousands of experts employed but ignored by the State at present.

“It is time that we all have to accept our responsibilities at all levels… and act decisively on matters that will determine the quality and quantity of medical care for this and future generations in South Africa and Africa. Time is running out,” Prof. Smit says.
 

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