TITLE:
Determination of Total Galactose from Dried Blood Spots—Extensive Assay Evaluation of a CE-Marked Test-Kit
AUTHORS:
Ralph Fingerhut, Toni Torresani
KEYWORDS:
Newborn Screening; Galactosemia; Total Galactose
JOURNAL NAME:
Journal of Analytical Sciences, Methods and Instrumentation,
Vol.3 No.3,
September
25,
2013
ABSTRACT:
Most
newborn screening laboratories use CE-marked or FDA-approved test-kits, like in
routine clinical chemistry. National regulations require only minimal
evaluation from the customer, if the test-kits are used as specified by the
manufacturer. The microtiter-based kit-concept is often based on the
perception, that the laboratory always processes whole microtiter plates.
However, in the daily routine, this is rather a rare exception, which leads to
much higher costs per newborn, compared to the costs per assay in the
test-kits. In addition the amount of wasted resources is quite high. Performance
of the Neonatal Total Galactose kit from Perkin Elmer was tested. We have
determined specificity, limit of detection (LOD), limit of quantitation (LOQ), intra
and inter assay variation, recovery, stability of measuring signal and
reagents. Results were also compared with the Astoria Pacific Spot Check
System. In addition, we had (by chance) the opportunity to test 2 kits, which
were already expired for more than 3 years. LOD was 165 - 306 μmol/L and LOQ
475 - 703 μmol/L, depending on the definition of LOD/LOQ. Mean recovery was
112.8%, intra assay CVs were 11.3, 7.3, 4.0, and 3.0, and inter assay CVs 28.7,
15.9, 7.8, and 9.3, at 220, 590, 1200, and 2060 μmol/L respectively.
Reconstituted and mixed reagents must be used within some hours, and were
unstable even if stored at -20℃. However, if the reconstituted galactose substrate reagent and galactose
oxidase reagent were only mixed according to the daily requirements, and the
rest stored separately at -20℃,
they were stable for at least 12 days. The performance of the expired test-kits
did not differ from the others. The performance of the Total Galactose kit is comparable to other tests used for
newborn screening. However, we could significantly reduce the costs per newborn
and reduce unnecessary production of waste, by thorough validation and
modification of the assay procedures.