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Open AccessFeature PaperTechnical Note

A Simple Method to Overcome the “Floating Disc Problem” Using the GALT-Assay on the PerkinElmer GSP—Remeasurement on a Stand Alone Plate Fluorimeter

1
Swiss Newborn Screening Laboratory, University Children’s Hospital, 8032 Zurich, Switzerland
2
Children’s Research Center, 8032 Zurich, Switzerland
*
Author to whom correspondence should be addressed.
Academic Editor: Peter C.J.I. Schielen
Int. J. Neonatal Screen. 2016, 2(4), 11; https://doi.org/10.3390/ijns2040011
Received: 12 October 2016 / Revised: 8 November 2016 / Accepted: 11 November 2016 / Published: 17 November 2016
The Perkin Elmer Genetic Screening Processor (GSP)™ is a fully automated system for the processing of immunoassays for thyroid stimulating hormone (TSH), 17-hydroxyprogesterone (17-OHP), immuno reactive trypsin (IRT), biotinidase, and total T4, as well as enzymatic assays for total galactose and galactose-1-phosphate uridyltransferase (GALT) from dried blood spots (DBS). The system however, has one drawback: it cannot transfer samples from one microtiter plate to another. While this is not a problem for immunoassays, it makes enzymatic assays more problematic. The remaining DBS can either cause significant signal quenching, or they can increase fluorescence intensity, when the DBS are floating on the surface. The latter can cause false negative results, when GALT is measured for galactosaemia screening. To overcome this problem, an additional measurement step to check for floating disks is incorporated, leading to prevention of the affected measurements. However, this causes a secondary problem in this totally closed system. We detected floating disk signals in approx. 0.7% of all screening samples as well as quality control samples, which had to be repeated. We describe a simple method, which is just a re-measurement on a victor fluorescence reader, or any other plate fluorimeter, with filters for excitation wavelength 340 nm, and emission wavelength 405 nm. The introduction of this second-tier measurement made all repeat measurements unnecessary. View Full-Text
Keywords: newborn screening; NBS; galactosaemia; GALT newborn screening; NBS; galactosaemia; GALT
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Fingerhut, R.; Sluka, S.H.M. A Simple Method to Overcome the “Floating Disc Problem” Using the GALT-Assay on the PerkinElmer GSP—Remeasurement on a Stand Alone Plate Fluorimeter. Int. J. Neonatal Screen. 2016, 2, 11.

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