Table 1 Bioanalyzer data summary for DM1 direct blood PCR results

1, 2, 3, 5, 6, 7, 9 14, 17, 22, 23, 24, 30, 34, 38, 39

Heterozygote

Both gel and bioanalyzer data indicate bands or peaks, respectively, consistent with two alleles within the specified base pair range for a normal DM1 phenotype. Detected peaks were above the bioanalyzer’s assay 20 FU default threshold for both purified DNA and 10% whole blood. No further testing needed.

18, 20, 26, 29, 31, 32, 35

Heterozygote-Manual Call*

The purified DNA sample and 10% whole blood sample both indicate heterozygote. However, for 10% whole blood samples, agarose gel detection indicated low band intensity and bioanalyzer electropherogram peaks were under the 20 FU default threshold.

8, 11, 36

Gel: Homozygote Bioanalyzer: Heterozygote “Split-Peak”*

The PCR product(s) for this donor sample have an apparent split peak when detected by the Agilent bioanalyzer. Agarose gel data indicate a single band. If reported bioanalzyer resolution is accurate, the split peak would indicate a tandem repeat difference of 5–10 base pairs for these DM1 amplicons.

12, 13, 15, 19, 25, 27, 33, 37

Homozygote*

Both gel and bioanalyzer data indicate bands or peaks, respectively, consistent with one allele within the specified base pair range for a normal DM1 phenotype. Further testing is recommended to determine if there is a DM1 repeat expansion.

4, 10, 16, 21, 28, 40

Homozygote-Artifacts*

Agarose gel data for this sample indicate a single clear band for both purified DNA and 10% whole blood. However, for the more sensitive bioanalyzer studies, smaller peaks corresponding to larger base pair fragments were identified. We speculate these peaks are non-specific PCR amplification products. Peaks detected with the bioanalyzer, falling under the assay’s 20 FU default threshold, were interpreted as artifacts. Further testing would be required to determine DM1 status for this patient.