Impact of weekday on blood test results

I learnt a very interesting thing recently. From personal experience. If you've been following this blog recently, you know I switched to Daily Nocturnal Hemodiafiltration (HDF) to try and help with my increasing Serum Beta-2 Microglobulin (Beta-2m) levels. This toxin, one of the notorious 'middle molecules', does not get removed well with conventional low-flux dialysers and with conventional hemodialysis. I was advised to switch to Hemodiafiltration which is much better at removing these beasts from the blood.

My Beta-2m before switching to HDF (on 3rd June 2022) was 20,476 ng/ml. The normal range is 604 to 2,286 ng/ml. Yes, I know. My level was very high indeed. Here is a table that shows how my Beta-2m trended over the last one year.

The value is trending downwards apart from that blip in April this year. The trend is due to Daily Nocturnal HDF. However, notice the last column. The values are significantly lower (compared to the trend line) when I have got 3 days of continuous HDF compared to other values. This stands out quite clearly. The more the continuous days of dialysis I get , the lower the Beta-2m levels go.

Which, I know, seems quite intuitive. The more continuous dialysis you get, the more Beta-2m is removed from the body and the lower the level would go. But unfortunately, many of us don't keep that in mind.

This is a critical factor when it comes to measuring toxins that are removed by dialysis. I am guessing it wouldn't be that important for things that dialysis does not remove like Hemoglobin. I am not sure though.

But it is worth keeping this in mind. What is important in blood tests often, is the trend rather than the absolute value. So, best to stick to the same circumstances as much as possible - same lab, same time, same day of the week, same route to go to the lab. Ok, kidding about the last one.