It’s not cirrhosis

False positives can ruin your day

I don’t mind admitting that I’ve bypassed the NHS to see a specialist. The NHS works brilliantly when you need to be seen urgently – fast-track cancer referrals and A&E, for instance – but anything non-urgent comes up against bottlenecks in care.

I’m just too impatient when it comes to my health. My husband Henry disagrees with my knee-jerk response. He’s happy to let things take their course. The exception is his Audi A3 e-tron shiraz red (of course) where even the slightest buzz gets sent in to the garage for a quick fix.

Hold on to your buzz

I imagine that specialists frequently get asked to adjudicate when it comes to the matter of tests. The problem with screening for illnesses is that no test is perfect.

A good test requires two things: sensitivity for the illness in question and specificity to exclude anything else.

Take the PSA test for example. Prostate cancer is the third most common cancer for men to die from, but most men die from something else. However, it’s very treatable if caught in the early stages. The PSA test screens for a protein found normally in semen and also in blood. When the cut-off is set at a figure of 4, the sensitivity is 86% and the specificity is 33%. This means there will be few false negatives (missing the illness) but too many false positives (wrongly telling you that you’ve got the illness).

So the PSA test isn’t an ideal screening test for prostate cancer as it leads to over-investigation and undue anxiety. That’s why the NHS doesn’t recommend it routinely, although an increasing number of men are requesting it.

Then there’s the ELF test for liver fibrosis, which most GPs aren’t even aware of. The cut-off value of 10.5 for the detection of severe fibrosis has a sensitivity of 100% and specificity of 77%. So the ELF test shouldn’t miss the illness, but there’s a risk of sticking a shark’s fin on the goldfish.

These plots from a paper published in 2012 illustrate the fishy issue:

This was a study pitting liver biopsy against Fibroscan and the ELF test in about 100 patients. The stage of fibrosis, assessed on biopsy, is scored from F0 (none) to F6 (cirrhosis). The left-hand plot show the range of liver stiffness assessed with Fibroscan, and the right-hand plot shows the range of the ELF score, both for three groups of fibrosis severity. Fibroscan is clearly good at distinguishing between no or mild fibrosis and the severe end of the spectrum. With the ELF test, there’s overlap between all three groups, making discrimination difficult.

This is the sort of thing you don’t get told when you order an online blood test. Caveat emptor, as they say in the letters’ page of What Car. Except this is about your health rather than some second-hand automobile. Neither is it spelt out in the printout from the lab – or the doctor’s comment.

So I was interested (i.e., anxious) to see what the specialist would say. Perhaps I’d get my knuckles rapped for ordering a blood test as if buying something from Amazon with Prime delivery included. “A little knowledge is a dangerous thing,” as someone said. Except I’ve got my medical training to guide me. I wonder what the average online punter would make of it all.

Henry came along both for support and out of personal interest. His ELF test score had come back abnormal, too. So we’re both in the same boat of not being quite sure what to do – apart from stopping drinking, of course.

The specialist Dr M was personable and approachable. He’s clinical lead for gastroenterology in a nearby NHS hospital and is up-to-date with liver disease guidelines. He told us that a Fibroscan machine had been acquired by a hospital 10 miles away from us, but it was only for use within the prison service. He’d tried to refer a few of his own patients for a scan but had been turned down by a colleague.

It’s frustrating that innovative clinical services can be on the whim of the latest charitable initiative. One only hopes that the prison population have a better chance of achieving abstinence than the rest of the population. One gather that hooch can be enticingly strong stuff and access to Fibroscan is unlikely to change prisoners’ appetite for that.

In the light of the growing liver disease epidemic illustrated on the above 2008 NHS map for England, Dr M mentioned that the British Society of Gastroenterology was now recommending the general use of non-invasive screening like the ELF test and the FIB-4. However, he emphasised that these were only surrogate measures of liver disease and shouldn’t be relied upon in the same way as examining a slither of liver under the microscope. Presumably it would be primary care who would be tasked with this and the Royal College of General Practitioners are likely to balk at the size and cost of the challenge.

Putting our situation into context, Dr M said it was likely that we both had some degree of fibrosis, which was to be expected from our several decades of drinking at least moderately heavily, but that it was long way from compromising liver function, as both our sets of LFTs were normal. Some of that fibrosis may be reversible, but some may not. At least my normal liver ultrasound and an unremarkable abdominal examination excluded more advanced liver disease.

The bottom line of the consultation with Dr M is that he thought we’d made the appropriate changes to our lifestyle (stopping drinking in my case, seriously curbing drinking in Henry’s instance) and no further intervention – treatment or investigation – was warranted. It was reassuring to hear that our life expectancy would be unaffected.

I did ask Dr M whether having a Fibroscan would help to determine the extent of the fibrosis, but he responded by asking me how that would help. And he was absolutely right. I’ve made my choice. There’s no quick fix that will reverse 30 years of abusing my liver over just four weeks.

So where does that leave the average Joe/Jill Bloggs and their decision making about testing for liver damage? To ELF or not to ELF? It turns out that the problem with the ELF test isn’t so much the issue of false positives as delivering a result that may be exaggerated in some people. Still, it’s undeniably effective as a wake-up call. At the end of the day, liver damage is liver damage. But at least it’s not cirrhosis. Thank goodness for small mercies.

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