[Study on the specific diagnosis of meconium aspiration syndrome (MAS) with fluorometry]

Porphyrins are found in fetal urine, neonatal urine, amniotic fluid, and meconium. Zn-coproporphyrin (Zn-CP), which we identified in meconium, has two fluorescent peaks at 580 nm and 630 nm, and Coproporphyrin (CP), found in fetal urine, has one fluorescent peak at 620 nm, when both porphyrins are excited at 405 nm. In this study, the fluorescent peak at 580 nm was used to detect Zn-CP in neonatal urine, using the new index, that is the Urinary Fluorescence Meconium Index (UFMI); UFMI = F580-(F580 + F600)/2 [F: fluorescence intensity]. We obtained urine samples from neonates in these three groups: Group-I: Meconium Aspiration Syndrome (MAS; n = 3), Group-II: non-MAS with meconium stained amniotic fluid at delivery (n = 18), and Group-III: non-MAS with clear amniotic fluid at delivery (n = 25). The UMI (Urinary Meconium Index) was also measured by conventional optical absorbance. The results show that many false positive cases were observed in UMI, and that no false positive cases were observed in UFMI. These results lead one to speculate that Zn-CP, which is specific in meconium, is used in UFMI measurement, while UMI measurement by absorbance cannot exclude contamination by CP in neonatal urine, so Zn-CP and CP are measured all together. UFMI values reflected the clinical course of neonates. It is concluded that UFMI is a more sensitive method than UMI for the diagnosis of MAS.