@LaughingCat: "I’m asking what, given the potential for variations in genetic or phenotypic sex, it is exactly that determines the differences between interpreting male and female test results"
Practically all the supposed confusion about sex determination arises from the confusion of 'sex' with 'genitalia'. In more than 90% of people, the two things match. Some people are born with malformed genitals, just as some are born with malformed faces (cleft palate is a common deformity), hole in the heart, or an abnormal number of fingers & toes.
There are many possible developmental glitches, but none of them change the body's sex. It's the second most fundamental thing about us, after species. Every cell in your body is sexed. The sex of our cells determines a lot more than the physical layout of our bodies: it affects our entire body chemistry.
A Y chromosome can be detected in a blood sample by a simple, one-step test. If there is a Y chromosome, the sample is male.
Whether a person has the full reproductive capacity of their sex is a different question. If they don't, they have some sort of injury or developmental abnormality - reproduction is an outcome of sex, not the determinant. Their abnormality might make them look like the other sex, and even have most of the reproductive equipment, but no male person produces eggs; no female person produces sperm.
Anyway, as far as blood sampling for general health purposes goes, the question of sex has nothing at all to do with the subject's reproductive organs. It's a simple matter of whether their cells have a Y chromosome or not.