Is there a word for a piece of medical data about the body

Solution 1:

OED

vital sign n. †(a) evidence of viability (obsolete); (b) Medicine a clinical measurement that indicates the state of a patient's essential body functions, spec. pulse rate, respiration rate, blood pressure, or temperature; chiefly in plural.

1951 Science 18 May 581/2 Blood pressure, pulse, color, and other vital signs were within normal limits.

Also figurative:

1993 Lancet 19 June 1586/2 Meanwhile, the repeated postponements and rising arguments over who gets what in a national health plan..have directed attention to the political calendar and the drooping vital signs of the Clinton presidency.