“Just give me the figures.” Ever said that to a doctor who’s pussyfooting around how serious some illness is? If you’re lucky enough never to have been in that position, you may, if you have HIV, have said it when they tell you your CD4 count is ‘fine’. And we bet you’ve said it to a garage mechanic; or a plumber; or an insurance salesman.

This HTU is all about the figures. We can get through a lot of life operating on hunches, rules-of-thumb, maybe spiritual guidance. But for really important decisions, it helps to know how likely something is; how long it will last; what it will cost. Figures sharpen the world, bringing into focus things that seem blurry.

But to use them you have to read them right. Caroline Sabin’s beginners’ guide to interpreting drug trials (See Making sense of randomised trials) shows that things are not always as reported. Newspapers love miracle cures and wonder drugs, and HIV research has had a history of false dawns and disappointments. Last month, for instance, the media was getting very excited about bananas and reporting that a substance found in everyone’s favourite phallic fruit worked better against HIV than two current drugs.

What researchers had actually found was that, in test tube trials, the banana compound was better able to prevent HIV from entering cells than two drugs – maraviroc and T20 – that also blocked entry, and might make a suitable candidate for inclusion in an experimental microbicide. Not a pill. But all the newspapers heard was “better than”, and they ran with it.

Of course, it works the other way too. For years, evidence has been slowly accumulating that, on the whole, it’s better to be on HIV drugs than not. From the SMART trial onwards at least, virtually all studies comparing people on HIV treatment to people off it show a lower mortality in people on the pills.    

The effect this has had on mortality is impressive, so much so that you sometimes hear that “there’s no reason why someone diagnosed with HIV today can’t have a normal lifespan”. People hear this and then understandably get very cross when they apply for, let’s say, life insurance and get turned down, or priced out.

Despite there being more options for HIV-positive people than there were (see Securing your future), insurance underwriters are hard-nosed businesspeople making broad-based decisions about risk and, as the piece on life expectancy (see How long have I got, doc?) describes, there is not a single, simple answer to this question in the case of HIV.

What studies actually show is that for some people, in some settings, life expectancy with HIV is approaching normality. For a lot of the rest of us, it still prunes off at least as many years as smoking 20 cigarettes a day would.

Sharpening the focus on the data doesn’t always bring reassurance. Sometimes it brings an exact appreciation of the work we have left to do to conquer this virus.