47,106,107 FTA paper carries the advantage of inactivating highly pathogenic organisms to allow safe transportation, with reported complete inactivation of Y-27632 side effects highly pathogenic Avian Influenza Virus (AIV) 1 hour after adsorption onto FTA paper.108 However, more evaluation of the potential infectiousness of different pathogens on DBS is needed. Contamination risks. Manual or automated punch devices, such as handheld office punches or automated machines (like the devices used for neonatal screening), are suitable for removing paper discs from DBS. There is a potential risk of carryover contamination that can be avoided by cleaning the punch device with bleach or related products and punching sterile blank paper between samples.
Recently, perforated filter paper cards have become available (Whatman and PerkinElmer), allowing the spots to be removed with a pipette tip, obviating the need for punching machines and reducing contamination risks. Selecting an assay. For quantitative assays, adjusting the cutoff for DBS samples compared with whole blood or serum may improve sensitivity and/or specificity, depending on the required balance between them.34 Assays that use a relatively small quantity of plasma/serum that is first diluted with sample buffer are more suitable for DBS samples than assays requiring large quantities. Attempts to keep DBS elution comparable with serum/plasma according to the manufacturer’s recommendations will greatly improve the chances that results of assays on DBS and standard samples will have comparable accuracy.
The quantity of serum in whole blood dried on filter paper is difficult to determine but essential for protocol development. Factors, such as hematocrit, blood volume per spot, and filter paper characteristics, contribute to different extraction yields of a DBS sample.109 Certain pathogens, such as HIV, are present in large quantities in whole blood (up to 104 copies per drop), whereas others, such as Salmonella enterica serovar Typhi and Orientia tsutsugamushi, are present at very low density. DBS as an alternative to standard samples is only possible if the pathogen is present in sufficient numbers for nucleic acid amplification. Reporting DBS evaluation studies. The Standards for Reporting of Diagnostic Accuracy (STARD) guidelines110 are an important starting point for assessing DBS evaluations. Many studies evaluating filter paper do not include full details on the paper type or processing, key information regarding reference standards, and use of appropriate statistical tests. In Table 6, we propose additional points to the current Cilengitide STARD checklist to address these issues.