Recent and long-lasting infections: the need for avidity testing in HIV-1 infected subjects.

Standard serological tests have reached high levels of sensitivity and reproducibility but do not indicate whether infection is recent or long-standing. Among the 59960 sera analyzed for HIV positivity at the Retrovirus Laboratory, Operative Unit of Microbiology, Bologna, Italy, from January 2010 to July 2011, 134 samples showed an initial positive result. Application of the avidity test, able to distinguish between recent or long-standing HIV infection, classified 59 subjects as recently infected and 75 as chronically infected. Besides all the public health implications, the distinction between acute and chronic infection might serve to establish the time of infection and therefore reach any potential partners who might have been infected in a specific period of time. Although our results are limited to subjects referred to our laboratory and hence represent only a limited part of the problem, the routine application of methods able to distinguish recent from long-lasting infection could help monitor disease incidence, identify high-risk groups, and enhance epidemiological conclusions.