HIV RNA tests

HIV RNA tests are primarily used to monitor progression in people already diagnosed with HIV and provide information about people’s viral loads. They are also commonly used to screen blood donations.

Because HIV RNA is detectable considerably sooner than antibodies, many in the United States are enthusiastic about the potential of RNA testing to help diagnose primary infection.

Rather than run separate for each patients (which would be expensive), the Americans test pooled samples of blood. In other words, samples are stored until there are 90 to test. If the pool tests negative, then all the samples are deemed to be negative. However, if the pool tests positive, then smaller pools of 10 are tested, until each of the samples with HIV are isolated.¹

However critics point out that in most settings, it takes several days to accumulate enough samples to be pooled, and that sending samples to a regional centre also incurs delays. In the United States, it typically takes 14 days to get results, which is arguably too long when diagnosing primary infection.

Moreover third-generation tests are still routinely used in the US, and whilst RNA testing may have a strong advantage over those tests, British doctors have tended to argue that RNA testing offers few advantages over fourth-generation tests.