after a tubal ligation and urine PG test

Why do lots of women that have had a tubal sterilization procedure say they have had negative urine pregnancy tests and a positive blood test? Why would it matter if ur tubes are connected or not? Confused on this topic in our discussion. Just wanting an answer for them all and curious.  Mine was positive urine with TL.

[adgal]

I don't think it has anything to do with tubal ligation.  You can get a negative urine test and a positive blood test because HCG (the hormone your body produces when you are pregnant) shows up in the blood earlier then urine.  So you can have a very low concentration in your urine, not enough for a urine test to pick up, but a high enough concentration in your blood for a positive.  It is just a few days apart though.  

Also, false negatives on home tests are common, typically due to not using them properly. For example, first morning urine tends to work best as your urine is very concentrated.  Drinking water can dilute it, or regular emptying of bladder.  Other reasons include not holding the test strip in long enough, or if you aren't using a cup, missing it, etc.  It happens.  Blood tests are typically the best way to know for certain.  But as for tubal ligation...that is not a factor as far as I know.