'High viral load' should mean over half a million copies, not over 100,000, Rome study suggests

A study by the University of Rome has found that a substantial proportion of patients with HIV are being diagnosed with viral loads of over half a million copies/ml, and it is these patients who are at raised risk of treatment failure when they begin antiretroviral therapy, rather than patients with viral loads over the conventional 'high' threshold of 100,000 copies/ml.

Professor Carlo Perno told the 13^th European AIDS Conference (EACS) that the average viral load in a cohort of 1430 patients starting antiretroviral therapy between 2006 and 2009 was in fact 125,000 copies/ml. The average CD4 count was 202 cells/mm³.

The study found that the most popular first-line treatment regimens were tenofovir/FTC/boosted lopinavir (Truvada/Kaletra)  and tenofovir/FTC/efavirenz (Atripla): using protease inhibitors in first-line treatment is more popular in Italy than the United Kingdom.

Professor Perno divided the patients into strata according to their viral load on starting treatment and found that roughly a quarter of patients each had viral loads below 30,000 copies/ml (30K); between 30K and 100K; and between 100K and 300K. Ten per cent had viral loads between 300K and 500K and 15% over 500K.

For the entire cohort the median time taken after starting therapy to reach a viral load below 50 copies/ml was 18 weeks, with 90% virally suppressed by week 48. This rate of viral suppression was on an intention-to-treat analysis, which included people changing therapy for non-virological reasons, stopping therapy or being lost to follow-up. In an on-treatment analysis restricted to people staying on their first-line therapy, the average time to 50 copies/ml was 16 weeks and 94% were virally suppressed by week 48.

The average time to a viral load below 50 copies/ml and the percentage undetectable at week 48 was as follows for the five viral load strata, on an on-treatment analysis:

Viral load      Time to 50 copies/ml      Below 50 copies/ml at week 48

Below 30K        10 weeks                              99%

30-100K            15 weeks                              98%

100-300K          18 weeks                              93%

300-500K          22 weeks                              93%

Over 500K         23 weeks                              84%

Compared with patients with pre-treatment viral loads under 30,000 copies/ml, the patients in the other four viral load strata were respectively 40%, 64%, 64% and 77% more likely to fail to achieve viral loads under 50 copies/ml at week 48.

One in ten patients with pre-treatment viral loads over 500,000 copies/ml who had achieved a viral load under 50 copies/ml by week 24 of treatment subsequently rebounded, compared with 5.4% with viral loads between 30,000 and 500,000 and 3.1% with viral loads below 30,000 copies/ml.

Professor Perno commented: “Patients with viral loads over 500,000 copies/ml represent a significant population, at higher risk of virologic failure and rebound, that may deserve special attention, and a selected therapeutic approach.” He suggested that the concept of 'high viral load' needed to be revised.