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Simple risk score can identify gay men who may have acute HIV infection
Roger Pebody, 2017-03-07 07:10:00

Seven simple questions about symptoms and risk factors identified three-quarters of gay men in Amsterdam who have acute (very recent) HIV infection, according to a study presented at the Conference on Retroviruses and Opportunistic Infections (CROI 2017) in Seattle last month. Using this risk score could identify gay men requiring HIV RNA testing (which can detect acute infections) in addition to HIV antibody testing.

Promptly diagnosing people who have acute HIV infection is important from both an individual and a public health perspective. But, diagnosis is challenging because the symptoms of acute infection can be caused by other common health problems like the flu and the most commonly used tests cannot detect the most recent infections. The alternative tests for HIV RNA are expensive and there are no clear guidelines on when to use them.

Researchers analysed data from 1562 men who have sex with men enrolled in the Amsterdam Cohort Studies. At 17,271 study visits men tested HIV-negative, while at 175 visits they had recently acquired HIV. The men had provided data on their health (including whether they had experienced 14 symptoms associated with HIV seroconversion) and sexual behaviour.

The researchers examined the factors associated with acquiring HIV. Two multivariable logistic regression models were constructed: one including only symptoms and one combining symptoms with other risk factors, using generalised estimating equations.

Several risk scores were tested. The optimal one included both symptoms and risk factors, assessed over the previous six months:

  • Fever 1.6
  • Swollen lymph nodes 1.5
  • Oral thrush 1.7
  • Weight loss 0.9
  • Receptive anal sex without a condom 1.1
  • More than five sexual partners 0.9
  • Gonorrhoea 1.6

The cut-off for the score is 1.5, meaning that any man with one of the first three symptoms or gonorrhoea would be recommended to be tested for acute HIV. Equally, a combination of any two (or more) factors would be an indication that further testing is appropriate.

Using this risk score with members of the Amsterdam Cohort would indicate that 24% should be tested for HIV RNA. In terms of sensitivity, the risk score identified 76% of men with acute infection.

Validating the risk score with a different cohort, the Multicenter AIDS Cohort Study (MACS) from the United States, 12% of participants would be recommended for further testing, but the risk score was less sensitive – 56% of men with acute infection would be identified.

The area under the curve (AUC) was 0.82 for the Amsterdam Cohort and 0.78 for MACS.

Different score cut-offs could be used, depending on the local context, local prevalence of acute infection, cost of a false positive and cost of a false negative. A lower cut-off would result in fewer cases of acute infection being missed but a larger proportion of men requiring testing.