Opt-out approach can boost HIV testing rates

Small changes in how an HIV test is offered make a big difference
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A large randomised study in an emergency department in San Francisco clearly shows that an ‘opt-out’ approach to seeking consent for HIV testing can increase the number of people who take the test.

The proportion tested ranged from 38 to 66%, depending on the wording used by staff offering HIV testing, Juan Carlos Montoy and colleagues reported in The BMJ last week. While the conclusions are not a surprise, this topic has not previously been evaluated in randomised studies (which provide the most reliable form of evidence).

Over a two year period 4800 patients at the emergency department of the San Francisco General Hospital were approached by non-clinical research staff and told: “We’re offering routine HIV tests to all of our patients. It’s a rapid test with results available in one to two hours.” 



A patient’s agreement to take a test or a treatment. In medical ethics, an adult who has mental capacity always has the right to refuse. 

drug interaction

A risky combination of drugs, when drug A interferes with the functioning of drug B. Blood levels of the drug may be lowered or raised, potentially interfering with effectiveness or making side-effects worse. Also known as a drug-drug interaction.


How well something works (in a research study). See also ‘effectiveness’.

Consent was sought in one of three ways, depending on which group the patient had been randomly allocated to:

  • “You can let me, your nurse, or your doctor know if you'd like a test today.” HIV testing was sought by 38.0% of patients in this ‘opt-in’ group.
  • “Would you like a test today?” HIV testing was sought by 51.3% of patients when this ‘active choice’ approach was taken.
  • “You will be tested unless you decline.” In the ‘opt-out’ group, 65.9% of patients took a test.

Similar patterns of test uptake were seen in different demographic groups and regardless of whether an individual reported sexual risk behaviour.

Small changes in wording therefore significantly affected patient’s behaviour – and the clinicians’ perception of their preferences. The authors note the subtle difference between ‘opt-in’ and ‘active choice’ although the two may often be conflated in everyday practice.

In the study there were large variations in acceptance rates according to which member of staff had approached the patient – even though the interaction was meant to be heavily scripted. In usual clinical practice, these variations are likely to be even greater.

The researchers note the wide variation in the proportion accepting a test in previous studies done in emergency departments. “The details of the testing regimen—including how the test is offered, by whom, to whom, and in what setting—can be crucial to how likely patients are to agree to be tested,” they say. They suggest that in routine practice, policies to offer testing in an ‘opt-out’ manner may be delivered by some staff members in ways which are not truly ‘opt-out’.

In an editorial, Jason Haukoos and Sarah Rowan comment: “To our knowledge, the study by Montoy and colleagues represents one of the largest trials to evaluate consent for HIV testing among emergency department patients, and the only one to do it in a randomized fashion but with particular focus on the efficacy of the various consent options… To maximize test acceptance and subsequent new HIV diagnoses, we must use evidence to drive decisions about the best way to conduct testing procedures.”


Carlos JCC et al. Patient choice in opt-in, active choice, and opt-out HIV screening: randomized clinical trial. The BMJ 352, 2016. (Full text freely available).

Haukoos JS & Rowan SE. Screening for HIV infection. The BMJ 352, 2016. (Subscription needed for access).