PTGDS and medium chain acyl-CoA dehydrogenase deficiency: AA, the physiological substrate of both the cyclooxygenase and 5-lipoxygenase pathways, seemed to be less active in stimulating PGD2 release from PBLs of MCAD patients than of healthy individuals, when expressed as PGD2 ratio (i.e. PGD2 level after AA stimulation divided by basal PGD2 release; Table 2): Median AA-triggered PGD2 ratio was significantly lower for MCAD patients (1.13; range: 0.20-3.26; including six non- or adverse-responder; P = 0.007) than for healthy controls (1.43; range: 0.88-2.46; one non-responder).