96 When comparing 903 and selleck chem Carfilzomib 226 filter papers, < 4�C5% difference was detected for analytes used for neonatal screening.96 FTA Elute and FTA (Whatman; GE Healthcare, Buckinghamshire, UK) are treated filter papers that lyse cells and inactivate antibodies, viruses, and bacteria but allow NAAT assays. Assays should not be transferred between paper types without additional evaluation. Sample collection and storage recommendations. Manufacturers' recommendations as well as the protocols presented by Mei and others14 and the US CDC97 provide useful guides. The WHO guidelines for HIV drug resistance testing with DBS and others contain a more detailed description of how to collect DBS samples (particularly for RNA viruses).96,98,99 A number of studies also examined HIV DNA and RNA storage conditions when validating DBS methods.

100�C103 For serology, specific collection and storage recommendations have been produced by the CDC.97 Collecting finger- or heel-prick blood with DBS is a fast and convenient method that requires minimal training. After the DBS sample has been dried for at least 3 hours, it should be stored in a zipped bag with desiccant to reduce humidity damage. If DBS are stored in freezers, ensure that they are dried thoroughly after being brought to room temperature to avoid condensation inside the bag. The effect of long-term storage at different temperatures on diagnostic accuracy of DBS has been investigated for only a few pathogens with variable results (e.g., HCV with poor/uncertain stability35,40 versus dengue, EBV, and measles with better stability).

47,49,52 Standardization of experimental methods for assessing DBS stability would help considerably. Recording the quality and integrity of filter paper samples on arrival at the laboratory is essential, as they can vary because of incorrect blood sampling or environmental factors, such as humidity, contamination, and mold overgrowth. The presence of nucleic acids or antibodies in venous and capillary blood may vary for different pathogens. Two studies suggest that dengue virus capillary viremia may be more prolonged than venous viremia,43,104 Brefeldin_A suggesting that it would be important, in an evaluation of NS1 assays and NAATs, that both DBS and liquid blood samples are compared using capillary blood. Biosafety issues. Because DBS contain dried blood, regardless of the pathogen being investigated, the samples should be processed as potentially infectious material, and health and safety regulations should be followed. However, safety and packaging requirements are simpler than for liquid blood, and DBS can be shipped as non-regulated, exempt materials.