Epigenetic analysis of RASSF1A gene in cell-free DNA in amniotic fluid.

ence in the LX 20 phosphorus assay. The occurrence of severe hyperphosphatemia during treatment with high-dose liposomal amphotericin was reported in a pediatric patient (3 ), but the possibility of pseudohyperphosphatemia caused by interference of liposomal amphotericin B in the phosphorus assay was not addressed. In this pediatric case, the phosphorus assay was performed on a Synchron LX20 analyzer (Chris Jarvinen, personal communication, January 20, 2006). It may be worthwhile to investigate the potential for AmBisome interference on other analyzers that use a phosphomolybdate ultraviolet assay from other manufacturers. The Johnson and Johnson Vitros analyzer and the Bayer Advia analyzer also use a phosphomolybdate method but use different reaction timing and wavelength measurements than the Synchron LX20, which might minimize susceptibility to AmBisome interference. AmBisome consists of amphotericin B intercalated into a unilamellar bilayer vesicle consisting of phospholipids and cholesterol and measuring 100 nm in diameter. We postulate that biodegradation of the liposomal vehicle may lead to interference due to light scatter or precipitation that affects the absorbance measurements. In patients receiving liposomal amphotericin B, interference in the Synchron LX20 phosphorus assay may lead to unnecessary treatment with phosphorus-binding agents. These cases illustrate the importance of evaluating the potential role of assay interferences in unexplained abnormal laboratory results. The current observations should also motivate testing of other liposomal-based pharmaceutical agents for similar interference. Liposomal agents currently available include liposomal doxorubicin (Doxil, Ortho Biotech Products) and liposomal morphine sulfate (Depodur, Endo Pharmaceuticals). Liposomal formulations of other drugs are currently in clinical trials.