The study authors are concerned that the large reductions in deaths and improvements to health since people with HIV were given combinations of drugs (combination antiretroviral therapy) may be compromised because of this.
Using national data on HIV positive cases, the researchers tested patients for resistance to the antiretroviral drugs before embarking on the treatment. Tests were conducted on 2,357 patients between 1996 and 2003 - thus researchers could track if there were changes to resistance patterns as time went on.
They found that 335 people showed some degree of resistance to one or more antiretroviral drugs in total. Most of these people - 257 - were resistant to drugs within one class only, 44 cases showed resistance to drugs within two classes and 34 showed resistance to drugs within all three commonly used drug classes.
Overall, this equates to a 14% rate of resistance to one or more of these drugs among the group studied over the whole time period. The resistance had reached an estimated 19% for the most recent time period of 2002-2003.
The UK's 14% rate of resistance was considerably higher than the 7% estimate for chronically infected patients in the USA, 6% in France and 10% elsewhere in Europe. Direct comparisons should be treated cautiously, however, as different studies have used different definitions of resistance. Using a more conservative definition of resistance (high level resistance to at least one drug) gives an overall estimate of 9% for the UK for the years 1996-2003, with the rate being 12% in 2002-3.
The authors say: 'The United Kingdom has among the highest reported rates of primary resistance to HIV drugs worldwide. By limiting the therapeutic options for a significant number of patients, the secondary epidemic of drug resistant HIV represents a major clinical and public health problem.'