Haemophilus influenzae requires two accessory growth factors: factor X (hemin) and factor V (NAD, nicotinamide adenine dinucleotide). The X and V factor requirement is usually demonstrated by the absence of growth on porphyrin and NAD deficient but otherwise nutritionally adequate media except near paper disc impregnated with X and V factors.

Haemophilus species that require NAD will not grow on blood agar unless they are hemolytic and can release the NAD from the erythrocytes. However, they will grow well on blood agar near colonies of beta-hemolytic staphylococci, which are capable of providing NAD (see here).