In a paper published online in advance in Clinical Chemistry this week, researchers from Sequenom report having examined the fetal chromosome 22q11.2 by sequencing circulating cell-free fetal DNA obtained from maternal plasma from two patients with confirmed 22q11.2 deletion syndrome, and 14 women at low risk for fetal chromosomal abnormalities. "Using a technique similar to that used for sequencing-based fetal aneuploidy detection from maternal plasma, we detected a statistically significant loss of representation of a portion of chromosome 22q11.2 in both of the affected fetal samples," the team writes, adding that it found no such loss in any of the control samples.

And in a letter to the journal, the Mayo Clinic's Stefan Grebe and his colleagues warn that measuring 3-methoxytyramine via single reaction monitoring LC-MS/MS is subject to "substantial cross talk between MN and 3MT ion pairs," skewing results. "Calibration material containing MN and NMN, but not 3MT, was found to produce a measurable 3MT ion peak, although the ion pairs do not appear related." Overall, the authors say their experimental results suggest that "cross talk needs to be addressed and evaluated in any mass spectrometry assay, and if identified, appropriate actions should be taken to minimize cross talk interferences through chromatographic resolution."