Inhibition assay of ala dehydratase by succinyl acetone in tyrosinemia type 1: A rapid ht1 screening technique for resource constrained diagnostic setups

Succinyl acetone is a specific marker of tyrosinemia type I. The present study was undertaken to develop a simple and cost-effective quantitation method for succinyl acetone in dried blood spot (DBS) implementable in resource-constrained diagnostic settings. Spectrophotometric microassay based on the inhibitory effect of succinyl acetone on δ- aminolevulinate dehydratase (ALA-D) in erythrocytes, which catalyzes the formation of porphobilinogen from δ-aminolevulinic acid and is measured at 550nm. The reliability and suitability of the method for routine laboratory practice was assessed before the method was used for screening. Greater inhibition of ALA-D activity was observed when succinyl acetone was spiked to blood before spotting. The stability of succinyl acetone in DBS progressively deteriorated when stored at -800C. Among the 71 samples processed; an inhibition ranging from 2.75% to 55.47% was observed. The maximum inhibition of 63 - 73.47% was observed for a couple of the tyrosinemia true positive cases. The proposed method is useful for the mass screening of newborn babies for Tyrosinemia type I. This could ensure early detection and intervention while addressing the challenge of expenses involved in high-end technology, till the newborn becomes a universal reality.