The response rate for biological collection was satisfactory for cord blood and urine (more than 80% of women) but lower for milk collection. This can be explained because the rate of breast feeding was 68% (n=204) at delivery and 42% (n=126) accepted to collect milk for research purposes. This rate decreased to 48% (n=144) at 1 month postdelivery and 15% (n=46) accepted to collect it by then. No quality biomarker for preanalytical validation of milk or urine is available to our knowledge. Therefore, we focused our analyses on sample quality in serum and blood.
Biospecimen characterization and preanalytical validation is one of the major challenges facing modern biobanking.11
In this pilot survey, we performed a first evaluation of the collection, transport, processing, and storage methods of samples for the ELFE project. The average time to storage (from collection of blood and urine to storage at ultra-low temperature) was 25
h, which is similar to other large-scale studies (for example, the UK Biobank has an average time to archiving of 23
h) even if blood samples were not centrifuged in the clinic setting before shipping to the central laboratory, as it was done in UK Biobank, for instance.12
This process was a compromise between feasibility on a large scale and the requirements of many scientific investigations. We centralized and standardized processing in a single blood transfusion center to ensure a high-quality data trail. We used 2 geographically separate repositories. The secure data audit trail was maintained using quality management system ISO 9001–2008.
The use of health service infrastructure to collect biological samples at the maternity unit for epidemiological purposes is a challenge. Indeed, the conditions under which biological samples are collected and processed in the course of providing health care in maternity units could be inadequate for the measurement of less-stable biochemical markers of epidemiological interest, such as cytokines.13
The procedures used for sample collection, processing, and storage have a major impact on the future scientific usefulness of ELFE.14
Thus, about 20% of the blood samples were coagulated upon reception. This could be explained by practical reasons in the delivery room, such as immediate or delayed cord clamping, or other factors within control because of different conditions in the maternities (eg, high workload of staff); these could also be reasons for partially filled tubes as well as the lack of sufficient volume of available blood. These differing conditions between maternity units could explain the association between hospital private status and higher rate of coagulation. Private hospitals are less research oriented and have not the same academic background or practices as public maternity units. Moreover, coagulation was also more frequent when a needle was used for collection, probably because physiological adaptation to delivery trauma induces hypercoagulability in the newborn's blood.15
Consequently, all mechanical factors such as the syringe shearing force and mechanical pressure through aspiration induce platelet and tissue factor activation and coagulation. This activation is not induced by natural dripping of blood.
A quality control study was performed to test the robustness of the pilot sample handling and storage protocol, by measuring sCD40L, which is an indicator of the delay of exposure of serum to room temperature. It has been previously shown that the sCD40L levels in cord blood are lower than in peripheral blood, which further consolidates the results of this study in terms of cord blood–derived serum integrity.16
Finally, it should be kept in mind that although serum sample integrity was successfully assessed on the basis of sCD4OL assay, novel quality control tools (such as surveillance of freeze–thaw cycle temperatures) need to be developed to assess other types of preanalytical variation and to allow a more complete characterization of large cohort samples.
In this pilot survey, we validated the collection, transport, processing, and storage methods of samples for the ELFE project. A quality control study was performed to test the robustness of the pilot sample handling and storage protocol by measuring sCD40L, which is an indicator of the delay of exposure of serum to room temperature. Studies of serum sample integrity need to be more investigated, as preanalytical validation is one of the major challenges facing modern biobanking. In the mean time, it can be highly recommended to carefully record all potentially critical preanalytical variables, with tools such as a Standard PREanalytical Code (SPREC).17