The need for vigilance: False-negative screening for adenylosuccinate lyase deficiency caused by deribosylation of urinary biomarkers
Abstract
Objectives: Adenylosuccinate lyase deficiency (dADSL) is a rare inherited metabolic disorder. Biochemical diagnosis of the disease is based on the determination of enormously elevated urinary levels of succinylaminoimidazole carboxamide riboside (SAICA-riboside) and succinyladenosine (SAdo).
We report a case of false negative screening for dADSL caused by deribosylation of the urinary biomarkers SAICA-riboside and SAdo. Design and methods: A thin-layer chromatography (TLC) method with Pauly reagent detection of SAICA-riboside was used as a screening method.
High-performance liquid chromatography with diode-array detection (HPLC-DAD) and LC-MS/MS methods were used for the identification and quantitative determination of SAICA-riboside, SAdo, succinylaminoimidazole carboxamide (SAICA) and succinyladenine (SA). Results: Following a negative TLC screening in a known case of dADSL, we analyzed urine using HPLC-DAD.
The concentration of SAICA-riboside was 2.7 mmol/mol creatinine (below the TLC detection limit), and we detected the two abnormal metabolites identified by LC-MS/MS as SAICA and SA. We showed that SAICA and SA were produced by deribosylation of SAICA-riboside and SAdo in the patient's urine.
Studies performed by monitoring the production of SAICA and SA after the addition of SAICA-riboside and SAdo to the patient's urine and to urine samples from patients with urinary tract infections suggested that deribosylation is facilitated by bacterial enzymes. Conclusions: Screening methods for the diagnosis of dADSL may be falsely negative due to bacteria-mediated deribosylation of SAICA-riboside and SAdo.
HPLC-DAD or LC-MS/MS analyses allowing for simultaneous detection of SAICA-riboside, SAdo and their deribosylation products SAICA and SA should be preferentially used for the diagnosis of dADSL in urine.