Gay men and lesbians are routinely excluded from clinical trials for new treatments for sexual dysfunction, according to US research published last week. The question is whether this is a case of discrimination or just questionable experimental design.

Dr Brian Egleston and colleagues from the Fox Chase Cancer Centre, Philadelphia, wrote in the New England Journal of Medicine that 15 per cent of all US trials of drugs and treatments for sexual problems specifically excluded gays and lesbians from participating. Most of the trials in question looked into treatment of erectile dysfunction.

Clinical trials come in several flavours depending on how they are conducted and how much is already known about the treatment being studied.

Phase I and II trials are when a few people are given the treatment to see if it works and is safe. Phase III trials are when thousands of patients are recruited to study the treatment in more detail.

Dr Egleston’s work showed that 73 per cent of phase III trials listed on the US National Institute of Health’s clinical trials database explicitly insisted upon patients being heterosexual and, usually, in a stable relationship. Phase I, II and other types of trial were affected to a lesser extent. This exclusion is mainly confined to trials concerned with sexual function.

It is important to realise that this does not represent gay people being denied access to standard healthcare. It is troubling however that a straight patient who has had no luck with existing treatments can be invited by his doctor to participate in a trial where a gay patient won’t have the same opportunity, and won’t even be aware his sexuality is a barrier.

The US National Institute of Health, which monitors clinical trials in the USA, has guidelines which specifically state that people must not be excluded on grounds of sex or race unless this is appropriate to the research. Currently there are no rules about sexuality but this is currently under consideration. Essentially exclusion criteria exist to ensure that trials are safe and ask the right questions. So it would be fine to exclude vulnerable groups where there is a question of drug safety. Likewise for trials of erectile dysfunction treatment, obviously only men are included. Rules about exclusion criteria in the UK are less clear but they are likely to be reviewed on a case-by-case basis by local ethics committees.

So in a situation where hundreds or thousands of gay men with sexual problems are missing out on the opportunity to try new therapies one would assume there is a valid medical or safety reason why.

I contacted Professor Gerald Brock from the University of Western Ontario, currently the lead investigator in a trial of Viagra in men with diabetes to ask why his trial explicitly excluded gay men. He explained that in the case of this trial, the end points used were questionnaires. These questionnaires ask specific questions about sex with a female partner and are only “validated for vaginal intercourse”.

This would seem like a sensible reason if not for the fact that a great many trials take place which do not use straight-men-only methods. I put this suggestion to Dr Egleston who told me about a measure of sexual function for men that was used in research in his unit that can be used in heterosexual men, gay men and even single men.

The more troubling issue then is why some doctors and scientists choose research techniques which make it impossible to include gay and lesbian participants in their trials when clearly there is a precedent for more inclusive methodology.

In an interview last week, Dr Egleston said there was “no indication that people running the trials intended to discriminate against gays or lesbians”. But he suggested that it was more likely that people were using the less inclusive methods out of convention, referring to it as a “copy and paste issue”. Indeed, Professor Brock agreed that convention was part of the reason he used such methods but he also believed it produced the highest quality evidence.

In the west there are still areas where inequality exists between gay and straight people but it is generally taken for granted that healthcare isn’t one of them. While drugs, once tested and licensed, are generally made available on prescription to anyone who needs them, there is still real disparity where gays are denied the opportunity to participate in clinical trials. If this occurs as a consequence of using old-fashioned methods in the name of convention then researchers must take care in the future before questions are asked about what would look like discrimination to some.

For more from Daniel James, see here for his blog.