I bought these and they taste great. A Mexican buddy of mine at school let me have one and I was hooked. The only problem I had with these is that is was the Aldama brand and not Las Sevillanas but it is still a great tasting Oblea with cajeta and I plan to buy again.
The hook effect and false BFNs. Summarised, the hook effect is when someone continuously gets negative urine and blood tests but are actually pregnant. It happens because hcg levels are too high to register and is common with mothers carrying multiples or on older woman.
In positive uhCG POC tests, free and fixed antibodies bind hCG to form a sandwich; hCG is present in several variant forms that change in their concentrations at different stages of pregnancy. When in excess, intact hCG can saturate the antibodies, preventing sandwich formation (hook effect phenomenon).