The analysis of dried blood spot samples using liquid chromatography tandem mass spectrometry

Assays using dried blood samples have been in use for a number of years particularly for the diagnosis of inborn errors of metabolism. This sampling technique has been greatly helped by the sensitivity and specificity offered by liquid chromatography tandem mass spectrometry because of the limited amount of sample available for analysis. There are advantages for patients to take samples at home but these must be weighed against potential problems with the sampling technique. Some assays appear to work very well whilst others suffer from poor recovery because of adsorption of the analyte onto the filter paper. Some newer strategies including impregnation of the filter paper and filter filtration will be discussed. Calibration of assays and the problems with matrix matching of standards are also important issues that need to be addressed before an assay can be used routinely.