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. 2014 Dec;16(12):889-95.
doi: 10.1038/gim.2014.62. Epub 2014 May 29.

Postanalytical tools improve performance of newborn screening by tandem mass spectrometry

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Free PMC article

Postanalytical tools improve performance of newborn screening by tandem mass spectrometry

Patricia L Hall et al. Genet Med. 2014 Dec.
Free PMC article

Abstract

Purpose: The purpose of this study was to compare performance metrics of postanalytical interpretive tools of the Region 4 Stork collaborative project to the actual outcome based on cutoff values for amino acids and acylcarnitines selected by the California newborn screening program.

Methods: This study was a retrospective review of the outcome of 176,186 subjects born in California between 1 January and 30 June 2012. Raw data were uploaded to the Region 4 Stork Web portal as .csv files to calculate tool scores for 48 conditions simultaneously using a previously unpublished functionality, the tool runner. Scores for individual target conditions were deemed informative when equal or greater to the value representing the first percentile rank of known true-positive cases (17,099 cases in total).

Results: In the study period, the actual false-positive rate and positive predictive value were 0.26 and 10%, respectively. Utilization of the Region 4 Stork tools, simple interpretation rules, and second-tier tests could have achieved a false-positive rate as low as 0.02% and a positive predictive value >50% by replacing the cutoff system with Region 4 Stork tools as the primary method for postanalytical interpretation.

Conclusion: Region 4 Stork interpretive tools, second-tier tests, and other evidence-based interpretation rules could have reduced false-positive cases by up to 90% in California.

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Figures

Figure 1
Figure 1
The process to upload data batches to the R4S tool runner. Details of the design, content, and clinical utilization of the one-condition tools and dual-scatter plots have been reported previously. A recorded educational presentation is also available at http://www.mayomedicallaboratories.com/articles/hot-topic/2013/06-15-r4s-pt-3/index.html. R4S, Region 4 Stork.
Figure 2
Figure 2
The number of active cutoff values (n = 8,382) used by R4S participating sites (n = 151). The y axis represents the proportion that meets the validation criteria. A given cutoff value is considered validated when it remains within the target range defined in R4S and also within the 25–75 percentile range of all cutoff values posted by all sites. High and low target ranges are defined by percentiles of the cumulative reference and disease ranges but could be replaced by override values in case of significant overlap. Vertical and horizontal dotted lines indicate the median values (active cutoff values = 56; proportion within the validation criteria = 26%). R4S, Region 4 Stork.
Figure 3
Figure 3
The potential impact of R4S tools, interpretation rules, 2TTs, and other potential interventions on the number of FP cases that were reported in California (January to June 2012). (-) Indicates subtraction of cases from the residual FP count on the basis of the criterion listed next to the symbol. 2TT, second-tier test; FP, false positive; R4S, Region 4 Stork.

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