SLC25A13 and Tyrosinemia type 1: Genetic testing results takes weeks or months, but polymerase chain reaction (PCR) sreening for hot-spot mutations in SLC25A13 gene, serum pancreatic secretory trypsin inhibitor (PSTI), and blood/urine succinylacetone will differentiate most cases of NICCD from tyrosinemia type 1 within days.