A CASE REPORT OF FALSE POSITIVE FERRIC CHLORIDE TEST

Abstract

Phenylketonuria(PKU) is one among the
most well known of the aminoacidurias
due to primary or cofactor related defect of
the enzyme phenylalanine hydroxylase activity
causing accumulation of phenylalanine,
phenylketones and phenylamines
resulting in mental retardation.Increased
level of phenylketones in urine causes permanent
green colour by ferric chloride test,
a screening test for diagnosis of phenylketonuria.
An increased urinary level of metabolites
of phenylalanine is one of the criteria
for a biochemical diagnosis of classic
PKU. Here we report a false positive ferric
chloride test in a case leading to diagnosis
of phenylketonuria, but negative dinitrophenlyhydrazine
test and aminoacid profile
within normal limits in tandem mass spectrometry.