Thursday, 22 November 2012

HbA1c - A Good Measure?

(*pre-warning – I’m still old school and am working in percentages – to convert try here)

Every once in a while comes the judge of my success at being a person with Type 1.  As with most measures for us it comes down to a number. Whether it’s BG test results, number of hypos, waffy moments, total carbohydrates in a day, carb to insulin ratio, basal levels, etc, etc, it's all based around numbers. Here I feel advantaged as I quite like numerical stuff. My job involves a lot of Excel and that makes me happy. Hashtag = sad.  As a slight diversion I have real sympathy for any person managing diabetes who struggles with numbers. It must be an absolute nightmare to add to the challenge that we face. You have my deepest respect for the extra daily challenges involved.

Anyway, back to the HbA1c thing.  As the whole piece is about the test I thought it might be worth having a recap on what it is and what the number means.  

In simple terms it’s a measure of glycated or glycosylated haemoglobin  This is a form of haemoglobin that is measured to identify the average plasma glucose concentration over prolonged periods of time. Normal levels of glucose produce a normal amount of glycated haemoglobin  As the average amount of plasma glucose increases, the fraction of glycated haemoglobin increases in a predictable way. This serves as a marker for average blood glucose levels over the previous months prior to the measurement. There is a belief that it’s weighted towards the previous two to four weeks too. 

HbA1c is used by clinicians as a judge of control and can be a factor when considering treatment options including suitability for pumps etc.

Perfect then. Surely an average ‘score’ allows my team to see how well I’m doing at maintaining a good average BG level. Or maybe it doesn’t. As a numbers kind of guy I realise that an average, especially a mean is a very poor measure of numbers over time. For example the graph below shows 15 blood glucose tests (not me, I promise Doctor!) all outside a typical target range of 4-8 mmol/l (72 -144 mg/dl) yet the average is bang on the target at 6! Would you think the nine hypos here are a good thing?

And we’re not helped that our lows can’t normally go lower than around 2.5 whereas the highs can relatively easily get to high teens. How easy is that to skew an average? We haven’t got a chance really.

So where does my history lie? We’ll stick to recent times as that’s all I can remember relatively easily and records before then were written using multiple pens and both hands in the waiting room. So around March 2011 I was at 10.1%. A little hard work by me brought this down to 8.6%. A few months later and it was 8.2%. Fantastic downward graph that I knew I could keep improving before the bottom of the curve kicked in. Then Adam arrived and the first result last December came in at 7.6%. Absolutely chuffed about this and really proud that I’d hit the sevens. Especially proud as I know it’s not unusual for the first pump one to be a slight rise. I was convinced that further pumpwork would bring this to my target of 6.something without too much stress.  

The next test was around March this year and this again was downwards but not quite hitting my target. Still going in the right direction but I’ll admit to being a little disappointed with my 7.3%. 

And so the next blood tests were booked for last week and I turned up and volunteered my very generous veins to the nurse who duly removed a decent amount of blood and I left slightly squiffy (I never like my bloods being taken!) but still optimistic of a decent score.  Recent BGs had been good and floating around the waffy level quite frequently which should help the average.

Overall I’d say my control is a world away from where it was two years ago and the time taken with the help of my nearest and dearest is really making positive effects on my overall control of my condition. But – did you see that coming – I’m still not happy. On my personal scale of success at managing my condition I see anything starting with a 7 or 8 as failure. Which is harsh. I’ll speak with people online who are really struggling and trying their hardest to get under 10 and I don't think bad of them in the slightest. We each have our own personal challenge. I’ll encourage them and say that everything needs to be taken in perspective and they mustn’t feel like they have failed. At all. So for me to complain about wanting to achieve a 6.x is insensitive at best.  And on the flip I know of others who would view a 6.1 as absolute failure. An example would be Nigel Jenner from Diabetes UK as I recall here. It does come down to everyone’s target being important and at the same time each result isn’t a judgement; it’s just a very crude measure of something that gives the only real measure of long-term control without the use of CGM - I wish!

So it’s time to for me to reveal my score and also time for another graph! As I’ve said I was aiming for 6 point anything, with a previous measure of 7.3%. So after going to the Doctors’ Reception and asking nicely if my results were back I got the official verdict. Are you ready? Do you want to know what I was told? OK, here goes; “The Doctor has said Everything is 'fine'. Bye. Next.” No, no, no, no. No! My response surprised her a little bit but when I asked for a printout she seemed happy to supply it to me if only to get rid of the nutter in front of her – yes, that was me. So the two page printout of every detail of my bloods was returned and as always it takes a minute to find the number I wanted. There it was; the judge of worth and success of managing a condition that after 33 years I should have a grasp on. 7.2%. Yep, a massive 0.1% reduction. 0.1%! That surely is within permitted error margins. So effectively no change. Just to prove it here’s the graph to show the flattening of the curve.

After coming home, sulking and trying to find a bright side I turned to the oasis of optimism that is Google. Now apparently the target level for people with Type 1 is between 5.9% and 7.2% - depending on site visited. I was in! So why didn’t that cheer me up? I knew that to go online and sulk about ‘only’ getting a 7.2 would be a little crass. So I made comment about being a little down without shouting the number. It wasn’t appropriate; especially as the same day I was telling someone who’d just got a 8.7 that that was fantastic news for them because any progress is good progress, that they’d had less hypos and the HbA1c is hugely flawed as it’s an average. This showed to me I needed to go back to my first graph.  The numbers prove nothing really apart from that it really is a bad measure. But it’s also one that me, and others too, place a huge significance and fear on.

My control in the last year has been so much better and Adam has given me the freedom and flexibility I’ve never felt before. It’s this that I should be thinking of and realise that I cannot and should not be defined by a number.

Thanks for reading,


PS. I’m still desperate for my next one to start with a 6 though ;-)