I went for a quantitative blood hCG test on Monday. The result was 8.2. As I was only 9 days past ovulation then, I am still hoping this is a viable pregnancy and I went back today for another blood test. The lab told me I need a quantative dilution hCG test (double the cost of the first test). They said that it is done to check that my levels have doubled. Surely if they do another quantitative test and the level is at 16, then they have doubled? What is the dilution for? Am I being ripped off? I can’t find any information online that I can understand.
The test method is a photometric one, measured at 450 nM, only good up to 50 mIU/ml of beta-hCG. If you have a higher value than that the absorbance no longer follows Beer’s law, and you have to dilute the sample to bring it into the appropriate concentration.
Ok, but my first result was well under 50, so a doubling would be under 50 too, wouldn’t it?