STARHS

The Serological Testing Algorithm for Recent HIV Seroconversion (STARHS) is a generic name for a number of laboratory techniques which distinguish recent and established HIV infection.¹ They may also be known as incidence tests.

STARHS approaches depend on looking for specific antibody markers, which give different results in the months following infection. If a test gives a result below a pre-determined cut-off point, it is deemed to be a recent infection. The definition of ‘recent infection’ depends on the test used, but may be four to six months.

Understanding changes over time in the presence of different HIV antibodies is the basis of STARHS-based monitoring. The production of HIV-specific immunoglobulin M (IgM) normally peaks one to two weeks after infection, before falling to background levels; whilst levels of Immunoglobulin G (IgG) increase slowly over several months and are maintained during chronic infection.

• De-tuned assays can be used to retest samples which are known to be antibody-positive. They are only capable of detecting samples with a higher concentration of antibodies (associated with an established infection). People with recent infection will be identified by their negative result on the de-tuned test.
• The BED-CEIA assay measures the proportion of all IgG that is directed against HIV antigens (the proportion increases in long-standing infection).
• Avidity assays measure avidity (the strength of antibody-antigen binding), which increases in established infection.

Because of person-to-person variability in the development of immune response, STARHS techniques are not yet able to give an accurate or definitive date to an individual’s infection. They are only able to suggest rough timings, and have a large margin of error.

STARHS approaches have been developed in relation to HIV-1 subtype B , and are less accurate in relation to other subtypes and in people with very low CD4 cell counts. Inaccuracies in people taking combination therapy have been noted; it is not known whether use of post-exposure prophylaxis or pre-exposure prophylaxis could also affect results. Concurrent infections could also reduce the accuracy of STARHS.

In 2008, the Health Protection Agency began the roll-out of STARHS, with the objective of it becoming part of the routine public health monitoring of all newly diagnosed HIV infections in the country. STARHS will be used to help estimate the number of new infections in the population (incidence).

Establishing true incidence is important for several reasons. When HIV diagnoses go up, it is not clear whether this increase is the result of a success in promoting HIV testing, or of a failure in preventing HIV infection. Knowing whether infections are recent or not provides a more accurate picture of who in the population is at increased risk of HIV infection; will help target resources to the populations in greatest need; contributes to the monitoring and evaluation of HIV prevention initiatives and HIV testing strategies; and helps predict how prevalence (the total number of people with HIV) will change, and therefore the future human and economic costs of HIV.

Results of STARHS tests are returned to the laboratory which conducted HIV testing. At the clinician’s discretion, STARHS results may be discussed with the patient, but should be considered in the context of the patient’s clinical and behavioural history, as well as the limitations of the test.