I had thought that the stream of Holford’s comedy health/marketing e-mails had dried up, so I was surprised to see him tell his mailing list yesterday that “One in two daily drinkers have liver dysfunction”. Not, in itself, an implausible claim. However, the evidence Holford bases it on is, not surprisingly, completely inadequate – this is not encouraging, given that Holford is trying to promote himself as an expert in addiction.
Holford claims that:
A research study published last week in the journal Hepatology reports that 40% of 1039 people tested for liver function had high levels of liver enzymes called AST and/or ALT, which are a known indicator of increased risk of death from liver failure. Of these people, 44% admitted they drank on a daily basis and 26% said they drank more than government guidelines.
This study was based on participants who requested a LiverCheck – a home test [offered by Yorktest] which requires only a pin-prick sample of blood.
So far as I can tell – it’s not entirely clear from the e-mail – Holford is referring to this letter in the journal. Firstly, did I mention that it’s a letter, about 1 page long. There’s relatively little detail: while I’m sure a study was carried out, the bulk of the information on it is not contained in the letter (and, on this blog, we do like detail).
Secondly, the letter does not show what Holford says it does. You cannot use a study of people who have paid for a home liver test to draw conclusions about the population at large. The letter does not tell us about “One in two daily drinkers”: it just tells us about “One in two daily drinkers” who have self-selected to take the Livercheck test. It’s not clear how generalisable this will be, but there is plenty of reason for caution: the letter acknowledges that we are talking about the ‘worried well’; we are also talking about those who thought they had reason to take a Livercheck test, had the financial wherewithal to fund one, etc. Moreover, having taken a look over this letter I can’t seem to find the figures that Holford refers to in the letter – unless I am missing something.
Thirdly, the test used – the Livercheck test from Yorktest – is sub-optimal. This Livercheck test – even if the laboratory carrying out works with flawless accuracy – is not as detailed as a proper Abnormal Liver Function Test panel, and is subject to both false positives and false negatives. In other words, Holford has used a sub-optimal test on a self-selected – very likely non-representative – sample of subjects in order to make claims about liver function in the wider population. In a remarkable coincidence Health Products for Life happens to sell the Livercheck test referred to in this letter and in Holford’s e-mail.
One more concern: Holford is quite clear that some subjects in this study had used the Livercheck test as an alternative to going to their GP. The letter makes is clear (p. 1730) that “the stated reason for undertaking the test was alcohol misuse in the vast majority of patients”. This is worrying for a number of reasons:
- If people do have a problem with excess alcohol consumption, they should seek proper medical advice. It can be hard to cut back on one’s drinking.
- The Livercheck test risks false negatives: subjects might have been incorrectly reassured that their liver function is normal.
- If people drink to excess, they should cut back – regardless of Livercheck test results, and regardless of whether their liver has yet been damaged. Excess alcohol consumption can have a number of negative health effects, and – even if someone really has not yet damaged their liver – that does not mean that it is OK for them continue drinking excessively until their health is damaged. Of course, if you tell your GP that you drink too much – and ask for a liver function test – part of their response will be to tell you to cut back on the drinking; I am not sure whether a home test kit (especially if it tells someone that their liver is functioning normally) could be so persuasive.
What we see here is thus bad interpretation of research, with potentially worrying medical consequences. Given that Holford is currently promoting his expertise in addiction and additive substances, his misinterpretation of this study on alcohol and liver damage is rather worrying.