Background: Circulating cell-free DNA (ccfDNA) has been confirmed as a useful biomarker in cancer and pre-natal clinical practice. One of the main critical points in using ccfDNA is a lack of standardisation for sample processing methods, storage conditions, procedures for extraction, and quantification that can affect ccfDNA quality and quantity. We report the results obtained from the SPIDIA-DNAplas, one of the EU SPIDIA (Standardisation and improvement of generic pre-analytical tools and procedures for in vitro diagnostics) subprojects based on the implementation of an External Quality Assessment scheme for the evaluation of the influence of the pre-analytical phase on ccfDNA. This is the first reported quality control scheme targeting ccfDNA for pre-analytical phase studies. Methods: Fifty-six laboratories throughout Europe were recruited. The participating laboratories received the same plasma sample and extracted ccfDNA by using their own procedures, at defined plasma storage conditions, and sent the isolated ccfDNA to the SPIDIA facility for analyses. Laboratory performance was evaluated by using specific quality parameters such as ccfDNA integrity (by multiplex PCR) and yield (by qPCR). Results: The analysis of the ccfDNA extracted by the laboratories showed that most of them (53 of 56) were able to recover ccfDNA but only 12.5% recovered non-fragmented ccfDNA. Extraction methods specifically designed for ccfDNA preserved the integrity profile. Conclusions: The evidence-based results of the SPIDIA-DNAplas EQA have been proposed as a basis for the development of a Technical Specification by the European Committee for standardisation (CEN).

One purpose of the EC funded project, SPIDIA, is to develop evidence-based quality guidelines for the pre-analytical handling of blood samples for RNA molecular testing. To this end, two pan-European External Quality Assessments (EQAs) were implemented. Here we report the results of the second SPIDIA-RNA EQA. This second study included modifications in the protocol related to the blood collection process, the shipping conditions and pre-analytical specimen handling for participants. Participating laboratories received two identical proficiency blood specimens collected in tubes with or without an RNA stabilizer. For pre-defined specimen storage times and temperatures, laboratories were asked to perform RNA extraction from whole blood according to their usual procedure and to return extracted RNA to the SPIDIA facility for further analysis. These RNA samples were evaluated for purity, yield, integrity, stability, presence of interfering substances, and gene expression levels for the validated markers of RNA stability: FOS, IL1B, IL8, GAPDH, FOSB and TNFRSF10c. Analysis of the gene expression results of FOS, IL8, FOSB, and TNFRSF10c, however, indicated that the levels of these transcripts were significantly affected by blood collection tube type and storage temperature. These results demonstrated that only blood collection tubes containing a cellular RNA stabilizer allowed reliable gene expression analysis within 48 h from blood collection for all the genes investigated. The results of these two EQAs have been proposed for use in the development of a Technical Specification by the European Committee for Standardization.

Background: Inappropriate handling of blood samples might induce or repress gene expression and/or lead to RNA degradation affecting downstream analysis. In particular, sample transport is a critical step for biobanking or multicenter studies because of uncontrolled variables (i.e., unstable temperature). We report the results of a pilot study implemented within the EC funded SPIDIA project, aimed to investigate the role of transport and storage of blood samples containing and not containing an RNA stabilizer. Methods: Blood was collected from a single donor both in EDTA and in PAXgene Blood RNA tubes. Half of the samples were sent to a second laboratory both at room temperature and at 4°C, whereas the remaining samples were stored at room temperature and at 4°C. Gene expression of selected genes (c-FOS, IL-1β, IL-8, and GAPDH) known to be induced or repressed by ex vivo blood handling and of blood-mRNA quality biomarkers identified and validated within the SPIDIA project, which allow for monitoring changes in unstabilized blood samples after collection and during transport and storage, were analyzed by RT-qPCR. Results: If the shipment of blood in tubes not containing RNA stabilizer is not performed under a stable condition, gene profile studies can be affected by the effects of transport. Moreover, also controlled temperature shipment (4°C) can influence the expression of specific genes if blood is collected in tubes not containing a stabilizer. Conclusion: The use of dedicated biomarkers or time course experiments should be performed in order to verify potential bias on gene expression analysis due to sample shipment and storage conditions. Alternatively, the use of RNA stabilizer containing tubes can represent a reliable option to avoid ex vivo RNA changes.