The HIV viral load blog

The HIV Subtype Picture

If you live in the West, you might be a little surprised by the subhead on this map. In Western countries, we’re used to it being a given that subtype B is the most prevalent strain of HIV. This map is a great visualization of where the HIV epidemic actually stands in terms of subtype distribution and concentration.

It also makes it clear why there is such a great need for a subtype-independent viral load monitoring assay like our ExaVir Load. It’s not only because the traditional assays were developed for measuring subtype-B and are of limited use outside the Western world, but because the spread of that huge prevalence of other subtypes Westward is only a matter of time.

 

As far as our ExaVir Load’s performance goes, that whole map might as well be the same color. But with the diagnostics most prevalently in use today, we’re facing a problem in providing accurate disease monitoring. And the problem will only get bigger as subtypes continue to migrate and mix. 

This is why we’re continually developing diagnostics that are subtype-independent and why we believe it’s so important. We have every opportunity to be ready for when the need for such diagnostics can no longer be ignored, so let’s stay a step ahead this time. 

Watch How HIV Works

Do you know what Reverse Transcriptase (RT) is? For one thing, measuring it is what makes our ExaVir HIV viral load test unique. But unless you have a medical background, it’s hard to get your head around RT. That’s why I’m so happy someone sent me this YouTube video. It’s a bit thick on technical-speak but the animation is fantastic and the role of RT very well depicted.

RT is the perfect marker for measuring HIV viral load because a retrovirus, like HIV, requires a functional RT in order to be infectious. This means that by measuring RT activity we can accurately measure viral load regardless of subtype. If you have any other videos related to RT or HIV viral load please let me know.

HIV quiz widget

Here is an educational widget I heard about here at the 2008 International AIDS
Conference in Mexico City. It demonstrates the impact that the HIV
pandemic is having on children in a quick and clever way. Nice idea.

Get this widget!

Universal Action Now

The biggest health conference in the world is fast approaching! On August 3rd the foremost HIV experts from around the world will gather in Mexico City for AIDS 2008. The participants will total over 25,000 along with 3,000 from the international media. So you could definitely say the world will be watching.

The key to progress is sharing our insights and achievements, and AIDS 2008 is the biggest meeting ground for the minds working to fight HIV to present their work and pool their collective intelligence. Quite possibly the most important aspect of the conference is identifying where we have come up short in our response to HIV, and what we need to do about it to move forward.

The theme of this year’s conference is Universal Action Now. It’s a vital rallying cry and reminder that even though we’ve made a lot of progress in fighting the HIV pandemic, we must maintain as much a sense of urgency as ever if we are really going to beat it. AIDS 2008 will seek to accomplish this through fully opening up dialogue, not only in person at the conference but by utilizing the web, creating networks and establishing communication that goes far beyond the five days of the event itself.

The conference will also mark the first time an international AIDS conference has been held in Latin America. This will help highlight the growing HIV problem in this area and others that are often overlooked due to the massive scale of the HIV problem elsewhere. With the lessons that we learned the hard way in places like Africa, we have a great opportunity to stem the tide of HIV in countries where the infection rate is still relatively low. But only if we take universal action right now.

The three biggest myths about viral load monitoring in resource-limited settings

Through my work I’ve understood that there are many different perspectives on viral load monitoring (VLM). All of them are understandably products of their environment. Many of the beliefs people have regarding viral load monitoring were formed over a decade ago when there were only RNA-based HIV viral load testing platforms available.  In 2002 a new platform based on reverse transcriptase (RT) was introduced that made viral load monitoring more accessible without sacrificing reliability.

To those of you who are familiar with both platforms these myths may sound quite out of step with the times. But these opinions are widely held in many parts of the world, particularly in those parts of the world defined as resource-limited.

1. You don’t need viral load monitoring when you have CD4 testing
   HIV viral load tests and CD4 tests measure different things (see: What’s the difference between HIV viral load tests and CD4 tests). CD4 is an excellent test to see what condition the immune system is in. Viral load, on the other hand, detects how active the HIV virus is. Both these pieces of information are important for doctors to use when managing HIV.  That’s why in most developed nations, both tests are given as a routine part of HIV management.
2. Viral load monitoring is too expensive
   This was the impression made when viral load testing was introduced into Sub-Saharan Africa in the 1990’s.  The costs of the tests and equipment have come down significantly since then but the perception remains.  What people often fail to consider is the cost of not testing. A recent study(1) has suggested that frequent viral load and CD4 monitoring has the potential not only to add three quality-adjusted life years to patients’ lives, but save billions of dollars for struggling economies in Africa and elsewhere.
3. Viral load monitoring is impractical for resource-limited regions
   RNA-based platforms introduced in the 1990’s required delicate instruments and advanced laboratory conditions that are rare to find in resource limited settings. That all changed in 2002 when tests using reverse transcriptase (RT) as a marker where introduced. Today there is a test that can work in the resource limited settings but in many instances this perception remains an obstacle.

1. Vijayaraghavan A et al. Cost effectiveness of alternative
strategies for initiating and monitoring highly active
antiretroviral therapy in the developing world. Journal
of Acquired Immune Deficiency Syndrome. 2007 Sept
1;46(1):91-100.

The difference between HIV viral load and CD4 tests

CD4 and viral load are two of the key tests doctors use to manage HIV. But the tests themselves, what they measure, and how doctors use them are quite different. Below is a brief overview of how the two tests work.

CD4 tests measure the number of CD4 T-cells in the blood to gauge the strength of the immune system in the presence of HIV infection. CD4 is an excellent test in this respect and has been the primary indicator doctors have used to monitor the overall condition of the patient’s immune system. It is most useful in determining when an untreated patient needs to begin taking ARVs. The test is usually simple to perform and relatively cheap to administer which has lead to its widespread use.

The test has two main limitations with regard to HIV management. First, there are many factors, other than HIV activity, that can affect the amount of CD4 T-cells present in the blood at any given time. So the doctor cannot be sure if the CD4 value is caused by HIV activity or other factors. Second, it can take up to 6 months for HIV activity to be reflected in the CD4 count.

While CD4 measures the body’s reaction to the virus, the viral load test measures the number of virus particles in the blood directly. A low viral load indicates that HIV is not actively reproducing and that the immediate risk of disease progression is low. A high viral load means the virus is active and the infection will progress. The viral load test is a more reliable indicator of viral activity than the CD4 test and, as such, a more reliable indicator of disease progression. It is the most useful tool in determining whether or not antiretroviral drugs are working since treatment failure is first manifested by a rise in viral load. In virtually all cases, this rise in viral load occurs within a month or two of the cause of treatment failure. 

Historically, the viral load test has had one main drawback: While a mainstay of treatment in developed nations, it has been more difficult to perform in resource-limited settings. That’s because tests introduced in the mid 1990’s are developed around platforms that measure RNA. These tests are made with delicate equipment and require laboratory conditions that are uncommon in resource-limited clinics. The introduction of the world’s first viral load test that measured reverse transcriptase (RT) in 2002 changed all that. The RT platform now provides equivalent results with simple equipment and lower demands on the laboratory running the test.

Three reasons viral load monitoring matters

1. Patients. First and foremost, viral load monitoring (VLM) helps doctors manage HIV better, thus increasing the patients’ length and quality of life.  This not only makes their lives better, but that of their families as well. It also helps the community by keeping them productive and working longer.
2. Budgets. VLM helps makes the supply of ARVs go further.  Many nations have a limited supply of ARVs, so ensuring none of the drugs are wasted is a top priority. VLM is the most accurate way to detect treatment failure, and as such gives the best indication of when to stop using medication that is no longer working for a patient. It also helps determine the best time to begin treatment, so it isn’t initiated earlier than necessary.
   
3. Society. Stemming the spread of ARV resistance.  When treatment stops being effective and a patient continues taking the same ARVs, HIV can become resistant to the drugs. And if the patient passes on their infection, their resistant strain goes with it. With VLM to help detect treatment failure, the development of drug resistance can be minimized and treatment options for patients can be kept open.

Those are my top three. If you have other reasons, please feel free to share your view with a comment.

What’s a blog? Oh, right, a blog…

“Martyn you gotta have a blog” advised a US colleague. Blog…hmmm…blog. Yes well…BLOG. The mind boggled. I thought for a few minutes, could this be a new toothpaste, another way of saying I had a cold or just some new terminology to describe market share. I was stuck. Luckily, before I could make a twit of myself a friend came to the rescue. “Yes, your personal thoughts about viral load testing published on the web".

Ok, so here goes. I will attempt to share my views on HIV monitoring, provide information and possibly help stimulate some debate. I´ll try to post twice a week, depending on the weight of my inbox, and hope that the information I post creates comments and feedback. The editorial views will be mine and not necessarily those of my employees or our partners around the world. I hope the information provided will be a useful resource to those of you who want to learn more about HIV monitoring and how we can make this test more accessible to HIV patients around the globe.

Either way I hope you find this blog a useful resource. If you don’t, please let me know how I can improve it.

Cheers
Martyn