Quanitative Blood Tests

  I have a question regarding quantitative blood tests.  Will a quantitative test be affected at all if I am taking Ortho-Cyclen birth control pills and am a smoker?  My OBGYN ordered a quantitative blood test because I thought I might be pregnant and I had the blood taken yesterday and am awaiting the results and wanted to make sure smoking and Ortho-Cyclen wouldn't affect the results of the test.
  Also, I had blood taken last week for a qualitiatve test - will that affect my quantitative test results? I didn't think so but wanted to ask and be sure.
  
  One more question for you if you have time - can you tell me what the difference between a quantitative and qualitative blood test is and which is more accurate?  I had a qualitative test done about two weeks ago and it came back negative but the Dr. decided to do a quan. test anyway to alliviate some of my concerns.  Does that mean a qual. test is not reliable?  
  And is there ever anyway that one is testing too late for pregnancy on a home test or blood test. In other words, would it ever happen that a test would show a negative and not positive when it really was because there is too much hCG in the body?
  Thanks so much for your help!!  You are definitely more informative than my OBGYN is with me and you have helped answer many of my questions!  I appreciate all the time you put into this bulletin board.

Dear Jill:
Neither smoking nor birth control pills will alter the results of a urine or a blood pregnancy test.
A qualitative test gives a positive or negative answer. It is adjusted to detect a fixed amount of hCG, ususally 25 mIU/ml. A quantitative test measures any amount of hCG above 5 mIU/ml. Both tests are highly reliable. A quanitative test is miniammly more disciminating.
hCG is produced throughout pregnancy and the test will always be positive: one cannot test too late.
Keywords: hCG pregnancy tests
This information is provided for education purposes and is not a medical consultation. If you have specific questions, please speak with your physician.