Analysis of vanillylmandelic acid and homovanillic acid by UPLC-MS/MS in serum for diagnostic testing for neuroblastoma.

BACKGROUND: Vanillylmandelic acid (VMA) and homovanillic acid (HVA) are typically measured in urine for the diagnosis and monitoring of neuroblastoma, a tumor in children <5 y. A protocol for evaluation of serum VMA and HVA has been utilized at our institution for approximately 25 y, originally validated using high performance liquid chromatography (HPLC) with an electrochemical detector. We recently validated a serum VMA/HVA method by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

METHODS: After solvent extraction and clean up with Ultrafree centrifugal filters, samples were analyzed by UPLC-MS/MS in multiple reaction monitoring mode.

RESULTS: The assay was linear between 2 and 1000 ng/ml for VMA and HVA. Within run and run to run CVs were <5% for VMA at all levels, <10% for HVA at high levels, and <20% at low levels. Correlation with the HPLC method was acceptable with a constant bias. The reference interval for VMA by UPLC-MS/MS was determined to be ≤20 ng/ml, and HVA≤30 ng/ml. Original patient data comparing urine to serum showed diagnostic agreement >80% for both VMA and HVA.

CONCLUSION: Correlation of VMA and HVA was acceptable after adjustment of reference intervals. Collection of a single serum sample instead of 24-h urine collection saves time and improves accuracy of measurement due to difficulty of collecting a 24-h urine sample in infants and young children. UPLC-MS/MS also offers improved analyte specificity, improved signal to noise, and rapid analysis time.