Abstract
A PILOT STUDY OF MULTIPLEXED PROTEOMIC NEWBORN SCREENING FOR WILSON DISEASE IN WA STATE
Background:
Newborn Screening (NBS) is successful in identifying infants with fatal but treatable disorders enabling early intervention with favorable outcomes. Unfortunately, many congenital disorders in particular Wilson disease do not feature specific metabolic biomarkers nor analytical methods suitable for NBS even where highly effective preemptive treatments are available. In our recent study, we demonstrated that direct measurements of the ATP7B itself using multiplexed proteomic methods from dried blood spots can be highly diagnostic and utilized in population screening for Wilson disease. Through quantification of the extremely low abundance intracellular proteins in dried blood spots, patients with Wilson Disease are readily detected.
Methods:
A first-in-class proteomic-based in vitro diagnostic (IVD) reagent kit has been manufactured under the GMP facility for identification of the four new conditions (Wilson disease, X-linked agammaglobulinemia, Wiskott-Aldrich syndrome, and Adenosine Deaminase deficiency (ADAD) in a single-run multiplex assay from DBS by LC-MS/MS. Within the assay range, linearity, accuracy, and precision were acceptable. A pilot study screening newborns in WA state for targeted conditions was initiated after IRB approval. Genetic sequencing of samples with peptide concentrations below tentative cutoffs is used for confirmation.
Results:
Kit validation shows consistent performance and inject-to-inject time is < 3 minutes. 19,100 newborns have been screened to date. Gender, ethnicity, birthweight and time of collections were included in the analysis. No differences in gender, ethnicity or birthweight are observed for ATP7B peptides. Two potential cases (one likely carrier and one uncertain) have been identified for Wilson disease to date. The first case carried one pathogenic variant, p.Gly626Ala and one likely benign variant, pLeu1015=. ATP7B peptides were marginally below the cutoffs. The second case presented with two variants of uncertain significance, p.Pro610Leu and p.Arg1224Leu. ATP7P887 peptide was marginally below the cut off (71.0 pmol/L, cutoff=75.7) while ATP7B1056 peptide was in the normal range. The overall rates of false positive were very low for all four conditions.
Conclusion:
This study highlights the use of novel IVD assay demonstrating the feasibility of LC-MS/MS proteomics for NBS of Wilson disease and other inborn errors of immunity.