Will PET CT scan affect blood results

[JanetRosslyn]

I am due a PET CT scan on 1st August and have just been given a blood test appointment of 2nd August. Does anyone know if the 'radioactive stuff' they give in the scan will affect blood results, especially ESR and CRP?

Apparently there are no other blood dates available with my GP before my Rheumy appointment on 15th August.

I know I could go to the walk-in blood clinic at the hospital on a later date, but I'm loathe to do this unless it's really necessary as their results never appear on my NHS app - for some strange reason my Rheumy sees them but neither I nor my GP do.

[PMRpro Ambassador]

Shouldn't do - it is only labelled glucose they are infusing and it has a very short half life. Should be almost all out after 6 hours.

[JanetRosslyn in reply to PMRpro]

Thank you so much for the quick response. I can stop worrying now. Rheumy wasn't too happy with last tests and thought my recent covid may have affected them so I didn't want skewed results this time. X

[PMRpro Ambassador in reply to JanetRosslyn]

Covid will almost certainly have sent them up - for at least a couple of weeks and then it depends how much it hangs on.

[DeepThought2]

You get a a very low amount ( 200 bis 400 MBq equals a Picomol amount of the substance) of radioaktive Fluorodeoxyglucose (18F) injected - this compound acts mainly like glucose in your body. A significant portion of the radioactivity is excreted within several hours with the urine. Half life time for the rest is 110 minutes. After 24 h the radioactivity is virtually gone. So physiologically it is a tiny amount of sugar you get injected (which is metabolized) and the radioactivity should not affect any blood result. So I see no problem to get your blood tested the next day. Maybe if you find the PET-CT procedure stressful, some markers that react to stress might be affected; but again no strong stress effect on ESR and CRP 24 hours later is to be expected. Disclaimer: I have no medical background but I am biologist with quite some knowledge in biochemistry/metabolism.

[JanetRosslyn in reply to DeepThought2]

Fantastic news. Thank you so much for the detailed response. I wasn't entirely convinced by my doctors receptionist glib response of oh I'm sure it'll be okay... but it seems she was right. Thanks again

[PMRpro Ambassador in reply to JanetRosslyn]

Except we are basing our assessments on a bit of science!!!!

[Sallyaches]

When I had a PET scan I had to stop prednisone for 10 days so the inflammation was present to be seen in the scan. This would maybe send your CRP up. I was in a lot of pain for the test but had a strong result from it. I am not sure if you have to stop prednisone these days it may be worth you checking. I took my prednisone with me to the test and took it as soon as possible afterwards. Good luck

[PMRpro Ambassador in reply to Sallyaches]

Any pred interferes with a PET scan - there MUST be inflammation present to be seen

[MaryA_ in reply to PMRpro]

I just had a PET scan and my PMR showed up even though I am still on a low dose of prednisone. My Oncologist mentioned it to me on the follow up appointment. Made me feel validated!

[PMRpro Ambassador in reply to MaryA_]

Depends how low. They think that 7mg is low enough - I'm not entirely convinced.

[JanetRosslyn in reply to PMRpro]

Just rang the scan helpline and left a message... they had asked about steroids so I told them 1mg pred, but they didn't ask about other meds and I'm also on 25mg MTX... not sure if I need to stop this? Hopefully they'll call me back.

[PMRpro Ambassador in reply to JanetRosslyn]

The pred is low enough not to make much difference. I suppose the question remains as to how the MTX works - it isn't an antiinflammatory in the same sense but does it suppress the production of inflammation? Then all the PET scan can say is that the PMR is well controlled and not that it is no longer active. Which isn't the same thing at all.

[JanetRosslyn in reply to PMRpro]

Thank you. Yes, I was a bit puzzled. I'll ring them again if I don't hear from them in the next few days. Off to visit the inlaws in Yorkshire now for their 60th anniversary celebrations... quiet family meal... They've just called to say they got a card from The Queen....we didn't tell them we arranged it 😉 x

[PMRpro Ambassador in reply to JanetRosslyn]

Impressive - I managed nearly 50 years without killing him and I thought that was good going!!!!

Have a lovely time - at least the weather is more tolerable. Where in Yorkshire?

[JanetRosslyn in reply to PMRpro]

We're in Hornsea on the east coast. Beautiful x

[PMRpro Ambassador in reply to JanetRosslyn]

My daughter lives in Whitby, works in Scabs ED

[JanetRosslyn in reply to PMRpro]

I'm sure she's a lovely girl, but I hope I don't get to meet her this weekend 🙂 x

[PMRpro Ambassador in reply to JanetRosslyn]

So do I!!!! She does work an awful lot of weekends! Her husband has a bizarre rota in traffic police so she tries to arrange her working so she is off with him if she can - and anyway, Sunday is the best pay ... Even beats BH bonuses

[JanetRosslyn in reply to Sallyaches]

Thank you. I'm only on 1mg Pred now... Will be 8 weeks at that dose by the time they do the scan. They're aware of this and didn't ask me to stop, thankfully.