A screening system for detecting genetic risk markers of type 1 diabetes in dried blood spots.

BACKGROUND: Certain alleles among the genes that code for the human leukocyte antigens (HLA) confer susceptibility or resistance to the development of autoimmunity that causes type 1 diabetes (T1D). A number of ongoing diabetes research studies analyze dried blood spots (DBS) from newborn infants for HLA-D alleles to identify higher-risk children as early as possible. A commercially available assay to detect such alleles has recently become available using a dissociation- enhanced lanthanide fluorescence system found in many newborn screening laboratories. METHODS: We adapted the system for use with DBS and improved the sample set-up for greater efficiency. We also developed an independent system for data analysis based on a spreadsheet program. These modifications were applied to HLA-DQB1 gene locus (DQB) analysis of 117 newborn DBS, and the results we obtained were compared with independent reference values. RESULTS: Our assay modifications and independent data analysis improved sample throughput and result tabulation. DQB results from the modified assay were consistent with the reference values in all but one sample, which showed a partial match. CONCLUSIONS: The modifications described here make this commercially available assay more suitable for high-throughput applications such as newborn screening. Our results show that this system allows highly accurate detection of DQB alleles that influence T1D risk.

Proficiency testing outcomes of 3-hydroxyisovalerylcarnitine measurements by tandem mass spectrometry in newborn screening.

BACKGROUND: The use of tandem mass spectrometry (MS/MS) for the analysis of amino acids and acylcarnitines from dried-blood spots (DBS) has become routine practice in newborn screening laboratories. The Newborn Screening Quality Assurance Program (NSQAP) added 3-hydroxyisovalerylcarnitine (C5OH) into its routine quality control and proficiency testing (PT) DBS materials for MS/MS to assure the quality of C5OH screening. We report the results from NSQAP evaluations for C5OH-enriched DBS, and summarize participant screening practices based on their analytical methods. METHODS: NSQAP prepared C5OH-enriched DBS materials for its participants. Laboratories reported quantitative and qualitative results. Bias plots of quantitative results were constructed using reported data and the results were sorted by an analytical method. RESULTS: NSQAP participants reported PT specimen 3964 as outside of normal limits for C5OH. The mean C5OH value for derivatized and non-derivatized methods was 2.80 and 2.67 µmol/l, respectively. Reported data from other specimens showed a similar trend in derivatized vs. non-derivatized assay results. Differences in C5OH quantitative values were observed among laboratories using different internal standards. CONCLUSIONS: C5OH MS/MS measurements in DBS assays varied by method and the choice of internal standards. The use of NSQAP's DBS materials allows harmonization of C5OH measurements by newborn screening laboratories worldwide.