IgG serum tests

[glkmel]

How much might an IGG serum test vary every six weeks? Mine are At 525 and 528. Looking for what might expect. I know it’s just under the normal range. Where else might I look?

[Jm954 Administrator]

I would say those results are exactly the same, i.e. within the margin of error for the analysis. I think you can be confident that's a precise result.Jackie

[guzzifan]

As Jackie says, those results are exactly the same. Your lab's confidence limits for IgG are likely around +/- 10%. This means that if they analyse the same sample repeatedly in different batches of work on different days with different lot numbers of reagents, different calibration curves, etc., 95% of the results for the same sample will fall within +/- 10% of the mean value (and 5% will vary by more than that). Your lab will have its own confidence limits. Results on the same sample may vary between labs by more than that if the labs use different brands of analysers, reagents, and calibrators. Stick to the same lab.

There's more variance in lab results than a lot of people expect. Don't focus too closely on the numbers!

Cheers. -Jim.

[glkmel in reply to guzzifan]

Thanks. Just started getting IgG serum test levels, but have been treating CLL for 6.5 years and know numbers for CBC tests, etc.

[guzzifan in reply to glkmel]

Just for clarity, lab confidence limits will be different for different tests, so for example your haemoglobin levels should be much more precise than IgG levels.

[AussieNeil Partner Administrator]

My first four IgG test results in my first 3 years after diagnosis bounced around within a range of 0.4 from an average of 5.1.

[glkmel in reply to AussieNeil]

Thanks, that’s good to know. IgG was 850 (at OHSU when diagnosed, but 6.5 years later is in low 500s. Have blood drawn every 12 weeks, mostly at local lab. Thus my question. This sight I’ve gone to often and is very helpful.

[BeckyLUSA]

My levels are tested every 6 weeks at the time of my IVIG infusions. My numbers are right at high 400’s / low 500’s each time before I get my infusion. Never vary by more than 10-15 points. Same lab each time.