Biobanks facilitate research by collecting, storing and sharing samples. One of the major concerns that biobanks face is how to best maintain sample quality over long time periods. The AIDS Clinical Trial Group (ACTG) is one of biggest groups of HIV investigators in the world. Since 1987, ACTG has collected more than 2.5 million biological samples from over 200 clinical trials. These samples are stored in a central biobank. ACTG allows researchers to reuse samples for exploratory studies once original clinical trials are finished.
Standardizing Sample Handling in Laboratories and Biobanks
Biobanks can only compare samples of similar quality that have been processed in a similar way. ACTG has standardized their sample collection and storage processes to ensure that samples are of the highest quality and generate robust data.
ACTG operates multi-center clinical trials in multiple countries. Therefore, samples are not all collected and processed in the same laboratory. ACTG has developed external quality assurance programs to monitor laboratory performance and assay quality in all the different laboratories that process their samples. ACTG stores all data from this program and this data can be used to compare performance over time and in different laboratories. This allows the organization to monitor for intra- and inter-lab variability. Pre-analytical variability is a major cause of variable sample quality and can cause experimental errors (1).
Control Stocks Can Help Biobanks Limit Variability
As part of ACTG’s quality assurance program, they produce quality control materials such as HIV-1 control stocks made up to known concentrations. All HIV-1 assays run on ACTG samples must include this control material. This allows ACTG to evaluate assay performance in different laboratories. Data from the control stocks can also be used to standardize results from multiple labs in multi-center clinical trials.
However, standardized protocols and quality assurance programs do not always ensure that biobanks can maintain sample integrity over time during long-term storage. Therefore, researchers recently tested whether HIV-1 RNA levels were stable in plasma samples stored at -80°C for between 5.7 and 8.6 years at ACTG’s central biobank (2). They did this by measuring HIV-1 RNA levels in stored samples and comparing that to the HIV-1 RNA levels measured in the same samples when they were first collected. Therefore, each sample served as its own control in the experiment.
Control Stocks Allow Biobanks to Compare Data from Different Assays
The researchers had to address a common problem when designing this experiment. The assay used to measure HIV-1 levels in samples when they were first collected was no longer available. HIV-1 RNA levels were originally measured in each sample using the microwell plate version of the HIV-1 Monitor Test (Roche Diagnostic Systems, NJ, USA). When researchers decided to measure HIV-1 RNA levels in the same samples after more than 5 years of storage, they had to use the Cobas version of the HIV-1 Monitor Test as the microwell plate version had been discontinued. The scientists used ACTG’s control HIV-1 stocks in both sets of experiments so they could compare the data generated by the slightly different assays.
The researchers compared over 1,800 sample pairs generated from over 350 clinical trial participants. They found 92% agreement in the HIV-1 RNA levels measured in freshly collected samples and in the same samples stored for more than 5 years at -80°C.
This study shows the importance of standardizing protocols in biobanks whenever possible. It also shows the value of implementing external quality assurance programs and using control stocks/samples/materials so that data from different assays can be compared. These precautions help to limit preanalytical variability.
The results of this study imply that HIV-1 RNA copies are stable within plasma samples stored at -80°C in ACTG’s central biobank for at least 5 years. This result supports previously published data showing that HIV-1 RNA is stable in samples stored at -70°C for up to 9 years (3).
- NCI Best Practices for Biospecimen Resources. 2016
- Jennings et al. Use of external quality control material for HIV-1 RNA testing to assess the comparability of data generated in separate laboratories and the stability of HIV-1 RNA in samples after prolonged storage. Clin. Microbiol. 2018
- Baleriola et al. Stability of Hepatitis C Virus, HIV, and Hepatitis B Virus Nucleic Acids in Plasma Samples after Long-Term Storage at -20°C and -70°C. Clin. Microbiol. 2011.