Many solutions are available for sample tracking and identification. Emerging electronic sample labeling technologies such as radio frequency identification (RFID), as well as more traditional solutions, are described here. Using RFID to tag samples can reduce costs and errors in biobanking, providing important long-term benefits.
The example below illustrates the problem that will be addressed in this article. These excerpts, from the first few paragraphs of an article in The New York Times Magazine,1 describe a researcher searching for a specific sample at the Fox Chase Cancer Center in Philadelphia:
…She pushed aside vial after vial. “I know we still have him somewhere,” she yelled, her head still inside the freezer. “We’ve got serum from, like, 450,000 people.”
O’Connell grabbed a ragged cardboard box the size of a paperback book. “This is my treasure box,” she said. “I bet Ted’s in here.” The box held 56 tiny glass vials filled with clear blood serum… . Around each vial, on a thin piece of tape, someone had scribbled information about each sample. “That’s duck,” O’Connell said, raising a vial to eye level. She dropped it and grabbed the next one. “Woodchuck.” She shook her head. “Geez, somebody should organize this.” She lifted vials one at a time, reading labels, dropping them back into the box and muttering, “Duck… duck…human, not Ted…duck…woodchuck…human, not Ted…
Suddenly, she twirled to face me, arm extended, holding one tiny vial, grinning. “Here he is!” she said. “Ted Slavin.”
Dr. O’Connell’s experience of going through a sample box, looking for a specific sample, is annoying. But, there is a bigger problem here—the samples in the box are warming up and they are degrading. If this search takes too long or is repeated enough, all the samples might be rendered useless.
Separate from the issue of sample integrity, losing track of samples can wreak havoc both to the prestige and the financial standing of a biobank, as was illustrated by the discovery of untracked sample vials at the U.S. Army Medical Research Institute of Infectious Diseases in Fort Detrick, MD.2 Research was literally stopped for four months until an inventory of all 70,000 vials in more than 300 freezers was performed and all of the samples were accounted for. It is not too hard to imagine situations in which losing or switching samples can cost lives.
To add samples to a biobank, three things need to happen without fail.3 First, the sample has to be properly prepared; second, an accurate database entry needs to be made; and third, an unbreakable connection needs to be made between the results of steps 1 and 2.
Step 1: The physical sample
The first step will not be addressed here, except to say that standards for sample preparation are as diverse as the sample types themselves.
Step 2: The database entry
The second step is creating an accurate database entry that includes all of the supporting information for that sample. Cheryl Michels, President of Dataworks Development (Mountlake Terrace, WA) and a member of the Informatics Working Group at the International Society for Biological and Environmental Repositories (ISBER) (Bethesda, MD), put it very succinctly, “The stored material is only as good as the information that backs it up.”
Step 3: Connection between physical sample and database entry
The last step in accessioning a sample is perhaps less obvious—a robust connection between the physical sample and the database entry needs to be created. How does one make this connection and what are the consequences of the different solution to this problem?
In the not-too-distant past, sample databases were, at best, an organized laboratory notebook. These gradually moved to spreadsheets that had one important advantage—the database could be searched. For a small university lab with a small sample collection, a spreadsheet might still suffice. Spreadsheets, however, have significant flaws for this type of application. For example, when using a spreadsheet, how does one deal with many millions of samples, several tiers of authorizations needed to access sample data, accurately document shipments, log sample handling, labeling? The list goes on.
Sample tracking using LIMS software
Sample tracking modules in laboratory information management systems (LIMS) software packages such as STARLIMS (Hollywood, FL) , LABVANTAGE (Somerset, NJ), and LabWare (Wilmington, DE) are dedicated to dealing precisely with these issues, although they sometimes handle different aspects of the problem in different ways. LIMS programs are typically more comprehensive and provide record management for experiments, track reagent use, laboratory supplies, inventory, and so on.
Sample/freezer management software
Another type of program is sample/freezer management software. These packages are more focused and typically deal with accessioning samples, keeping track of them and the associated sample information. Examples of well-established freezer inventory packages are Freezerworks™ (Dataworks Development) and FreezerPro (RURO, Frederick, MD).
Sample identification technologies
Figure 1 – Sample vials are shown from a variety of vendors. On the left is a vial with a handwritten label. Next are two vials with laser-scribed sleeves with 1-D and 2-D barcodes, as well as human-readable text that fits over the vials. In the middle are vials with embedded 2-D barcodes. The two right vials have BioTillion RFID tags in the vial base. One of these vials has a redundant 2-D barcode. Any of the sleeveless vials can be labeled with a wraparound printed label if needed.
Simply put, the sample needs to be tagged in some way that is unique and identifiable. The major technologies that are used for uniquely identifying a sample are listed below (also see Figure 1). The examples given here are for cryogenic freezer vials, but many of the technologies are applicable to other types of samples, such as formalin-fixed, paraffin-embedded tissue blocks.
Whatever the solution one uses to track samples, an issue that requires some thought is that of standards. One does not want to label his or her samples and find out in several years that the labeling technology used is obsolete and that current technology cannot read the identifying information of the sample. Adhering to a standard reduces this risk. It also lessens the researcher’s dependence on single vendors of proprietary technology.
Location-based sample tracking
Perhaps the most tempting solution to the problem is not to label the samples at all and to identify the samples by their location. This might work well until the first sample box drops or is misplaced or, even worse, when a freezer fails and the samples need to be moved in a hurry. Even in a robotic system this is not a good idea, because in the end, how do you really know that this is the sample you think it is?
The oldest method, handwriting on the vials or on wraparound labels, is still used today. Only a limited amount of information can be written this way. While the cost is very low, a disadvantage is that handwriting can often be unreadable, sometimes even by the person who wrote it. In anything but the smallest biobank, this method is slow, cumbersome, and error prone. Also, inks and writing surfaces need to survive the wet and cold.
Labels that survive cryogenic temperatures are common today. They have an added advantage—they can be printed on demand by a variety of label printers. Again, vial–label compatibility needs to be tested. This author has seen a boxful of several thousand unlabeled frozen vials with thousands of unattached labels from a tropical disease expedition to South America. The value of the samples went to essentially zero because of an incompatible adhesive. The adhesives used have improved greatly in recent years, and special-purpose labels rarely fall off now.
Samples can also be labeled with a variety of barcodes. Because of their size, 1-D barcodes usually need to be read from the side, meaning that the sample needs to be removed from its container. Thus, samples must be handled in some way to identify them. Still, 1-D barcodes can be much more accurate than the machine-readable type.
On the other hand, 2-D barcodes are small and can be located on the bottom of a vial. This allows one to scan a whole box of vials at the same time, significantly reducing the time that the samples are being warmed.
Barcodes can be printed on a label printer and stuck onto the vial as needed, but they can be fused or etched into the sample vial as well. This significantly reduces the chance of losing the sample’s unique identifier.
It should be noted that the readability of these optically based labeling technologies suffers when samples are wet or covered with frost or ice. Scanning a box of 2-D bar-coded vials in a typical lab environment might require an alcohol wipe to de-ice the barcodes before scanning.
New, electronic sample labeling technologies are now emerging, most of which are variants of radio frequency identification. An RFID system has two basic components: a reader and one or more uniquely identifiable tags. The reader can wirelessly interact with the tags in different ways. Typically, the reader transmits a signal and listens for a tag-modified echo. The differences between the transmitted and received signal encode information from the tag.
Why do we need to add this complexity to solve the problem? There are several advantages of RFID over more traditional labeling: 1) They do not need to be visible to the reader, 2) reasonable amounts of frost and ice do not affect the reading, 3) typically there is user-writable memory in the tag, 4) the actual ID programmed into the tag can be significantly longer than that of a 2-D barcode, and finally 5) they can be made to operate at ultralow temperatures.
Several companies have entered this space in recent years. bluechiip (Scoresby, Victoria, Australia) has a proprietary microelectromechanical systems (MEMS)- based technology that allows the user to read a tag attached to a sample vial. An advantage to this system is that it allows the user to measure the temperature of the sample in real time when it is energized by the reader.
Perma Cryo Technologie (Kaiserstrasse, Germany) also has an RFID-based solution, but in addition to an RFID tag, it offers a programmable memory that is molded into the vial plastic. This chip can be used to store sample analysis results, for example. This chip needs to be plugged in to be accessed.
BioTillion (Skillman, NJ) labels each vial with RFID tags that comply with the EPC Gen2 international RFID standard. Once attached, the tag cannot be removed. Unlike the RFID-based solution from Perma Cryo, the BioTillion system does not store information about the sample with the physical sample. It simply provides a unique identifier that robustly links the sample to the information in the database. This significantly reduces the cost of the tag.
Figure 2 – The BoxMapper reading a box of RFID-tagged samples that were just removed from a vapor phase liquid nitrogen freezer. The BoxMapper provides a map of the sample box to the freezer inventory or LIMS software.
To read the RFID-tagged vials, BioTillion offers a box scanner (BoxMapper) (Figure 2) that provides a rapid method for mapping the samples to the row and column in the freezer box. Reasonable amounts of frost and ice do not affect the reading, and samples can be read when they are at liquid nitrogen temperatures. Since the scanning is quick, sample integrity is maintained because sample heating is kept to a minimum. Any discrepancy between the actual physical location of the vials and what is reported by the database can be easily flagged.
An important longer-term advantage of RFID-tagged samples is that the scanner technology described above can, with careful design, be implemented in the freezer itself. This would allow the freezer to inventory itself and report its contents to the user without removing samples from the freezer. If this can be implemented, the security of a biobank will increase because any changes to the contents would be associated with whoever accessed the freezer.
- Skloot, R. Taking the Least of You. The New York Times Magazine, Apr 16, 2006.
- Bhattacharjee, Y. Science 26 June 2009, 324, 1626.
- Biopreservation and Biobanking Apr 2012, 10(2), 79—161. doi:10.1089/ bio.2012.1022.
Hanan Davidowitz, Ph.D., is CEO, BioTillion, LLC, 30 Vreeland Dr., Ste. 7, Skillman, NJ 08558, U.S.A.; tel.: 609-454-3523; fax: 609-228-4433; e-mail: email@example.com.