The challenge panel for the first SUAC PT event contained 4 members of the pilot set of SUAC calibrators (specimens 3831-4) and 1 specimen from a DBS pool made of nonenriched hematocrit-adjusted blood from a single donor (specimen 3835).
The 5-specimen panel for the second PT event contained 3 members from the set of SUAC DBS calibrators (specimens 4832-4) and 1 each of DBS specimens from nonenriched and SUAC-enriched portions of a single unit of hematocrit-adjusted blood (Specimens 4831 and 4835, respectively).
An instruction page, a data report form, and a questionnaire pertaining to SUAC screening practices were enclosed with every PT specimen panel.
Participants were asked to report each PT specimen's SUAC concentration and its presumptive clinical classification (within or outside normal limits) and to respond to the screening practices questionnaire.
In general, each pilot-study laboratory recovered a consistent fraction of added SUAC across the concentration range tested (0-50 [micro]mol/L), but among the laboratories, recoveries of added SUAC ranged from approximately 25% to 200%.
We used paired data sets from the 6 laboratories that participated in both pilot surveys to compare, for each data set, the reported SUAC concentrations with the enriched SUAC concentrations of the pilot DBS materials.
After extraction of SUAC from the leftover dried filter paper spots, the eluates were transferred to another round-bottom 96-well plate and dried under heated (40 [degrees]C) nitrogen for approximately 7 min.
We performed method optimization for the detection of SUAC by selected reaction monitoring (SRM) by infusing a 10 [micro]mol/L solution of SUAC and its internal standard as hydrazones at 0.
DBS calibrators of SUAC at 5 different concentrations (0, 5, 20, 50, and 100 [micro]mol/L) showed detectable and reproducible signals with a linear response ([R.
We determined intraassay imprecision by performing 5 replicate analyses of samples with 5 different SUAC concentrations, 1.
We assessed the stability of extracted and prepared specimens by analysis of 23 newborn screening samples and 4 controls enriched with SUAC at 6.
We conducted a comparison using 290 newborn screening samples that were analyzed with and without the SUAC modification.