My idea was that the particular type of NF indicated (which in the two cases you've quoted clearly refers to an age group: a newborn and an adult) might refer to the category of numération (the test parameter) relevant to the patient in question.
For example, in this document (CATALOGUE DES EXAMENS DE BIOLOGIE MEDICALE) different NFs for different patient groups are indicated, albeit not the ones in your text:
"NUMERATION FORMULE SANGUINE (NFS) = HEMOGRAMME (dont les plaquettes) NF
Numération pour les nouveaux-nés (jusqu'à 6 mois) NFBB
Numération chez des patients suivis pour des affections hématologiques B50 NFHP 1106"
https://www.bioparisouest.com/uploads/docs/20140511-2108-179...I'm by no means sure it works for your text, but "NF" seems to occur a lot with this meaning in the context you're dealing with.