HCG doubling, time of day,etc.

  Hi--I know that you answer lot of questions about HCG but I hope that you can
  answer mine, too.  I am approximately 4 1/2 weeks pregnant (since LMP).  On Monday
  (1/11) my HCG was 331.  I had it done again at a different lab on Thursday (1/14)--
  three days later at a different lab and it was 656.  Is there variation between
  labs that could explain a less than doubling over 3 days.  Are my HCG values
  close enough to doubling that they are likely to be OK?  Does the time of day
  that the blood was drawn have an effect?
Dear Lorraine:
The time of day does not make a difference: hCG is not secreted in a daily cycle pattern. Compairison of values between different laboratories is difficult because of what is called inter-assay variation and because labs may use different standards giving a different absolute measure. The range of rise over 2-3 days is between 66% as the low at 2 days and 233% as the high at 3 days.
Serial values measured in the same laboratory would be the most helpful information.
This information is provided for education purposes and is not a medical consultation. If you have specific questionsxplease contact your physician.
Keywords: hCG