Related Experiment Video
Updated: Aug 5, 2025
In Vitro Enzyme Measurement to Test Pharmacological Chaperone Responsiveness in Fabry and Pompe Disease
Published on: December 20, 2017
Harmonization of Newborn Screening Results for Pompe Disease and Mucopolysaccharidosis Type I
M Christine Dorley1,2, George J Dizikes3, Charles Austin Pickens4
1Tennessee Department of Health, Division of Laboratory Services, Nashville, TN 37243, USA.
Insights
Harmonizing enzyme activities for newborn screening tests like Pompe and MPS I reduces false results. This study improved consistency across labs and methods, though cutoff placement still impacts final reporting.
Area of Science:
- Biochemistry
- Medical Diagnostics
- Public Health
Background:
- Newborn screening faces challenges with false-negative and false-positive results for conditions like Pompe disease and MPS I.
- Conservative cutoffs to prevent missed diagnoses increase false positives and lower predictive values.
- Methodological differences across laboratories further complicate accurate newborn screening.
Purpose of the Study:
- To harmonize enzyme activity measurements for Pompe and MPS I.
- To reduce false-negative and false-positive rates in newborn screening.
- To correct for variations between testing methods, specifically Tandem Mass Spectrometry (MS/MS) and Digital Microfluidics (DMF).
Main Methods:
- Enzyme activities for Pompe and MPS I were harmonized across different laboratories and testing platforms.
- Proof-of-concept calibrators, blanks, and contrived specimens were analyzed by participating states.
- Regression and multiples of the median statistical methods were employed for data harmonization.
Main Results:
- Variability in reported enzyme activities and established cutoffs was observed among laboratories.
- Six of seven MS/MS labs reported MPS I enzyme activity marginally above their cutoffs (classified as negative).
- All DMF labs reported the same specimen's MPS I enzyme activity below their cutoffs (classified as positive).
Conclusions:
- Harmonization achieved reasonable agreement in enzyme activities and cutoffs between laboratories and methods.
- Harmonization itself does not alter the final classification of a result.
- Cutoff placement remains a critical factor in determining the reporting of newborn screening results.
Abstract:
In newborn screening, false-negative results can be disastrous, leading to disability and death, while false-positive results contribute to parental anxiety and unnecessary follow-ups. Cutoffs are set conservatively to prevent missed cases for Pompe and MPS I, resulting in increased falsepositive results and lower positive predictive values. Harmonization has been proposed as a way to minimize false-negative and false-positive results and correct for method differences, so we harmonized enzyme activities for Pompe and MPS I across laboratories and testing methods (Tandem Mass Spectrometry (MS/MS) or Digital Microfluidics (DMF)). Participating states analyzed proofof- concept calibrators, blanks, and contrived specimens and reported enzyme activities, cutoffs, and other testing parameters to Tennessee. Regression and multiples of the median were used to harmonize the data. We observed varied cutoffs and results. Six of seven MS/MS labs reported enzyme activities for one specimen for MPS I marginally above their respective cutoffs with results classified as negative, whereas all DMF labs reported this specimen's enzyme activity below their respective cutoffs with results classified as positive. Reasonable agreement in enzyme activities and cutoffs was achieved with harmonization; however, harmonization does not change how a value would be reported as this is dependent on the placement of cutoffs.
