It is a question that is all too familiar in today’s labs. “We have to automate our laboratory, but how?”

The benefits of automation are profound. Productivity and accuracy improvements can be significant. However, some labs still rely on old-world methods of manual data tracking because they don’t think they can justify the investment or time commitment to automate. In reality, a simple bar-code scanner — a proven and reliable technology — holds the answer to automation.

Bar codes are a cost-effective technology available to automate many of the timeconsuming and error-prone processes taking place daily in your facilities. In fact, laboratories can scarcely automate today without bar codes. While other technologies may someday offer more cost-effective identification, bar codes are essential to automation efforts in today’s lab setting. Many labs are not only integrating bar-code scanning and printing to satisfy a customer requirement, but to streamline and improve their own operations.

When a national research project to investigate adolescent AIDS cases needed to manage numerous samples from multiple locations, it looked to bar codes to improve test data collection and track test results. Sixteen clinical sites in 13 cities were part of the study, feeding samples to two central laboratories for testing or storage. Each sample, typically blood or a gynecological specimen, needed to be uniquely identified as study participants make multiple visits per year where similar samples are taken.

A bar-coded identification system was implemented to track each person throughout the duration of the study with labels that identify the site, the subject number, the visit number, the nature of the sample, and similar samples from the same visit. Because of the complexity of information required to track the samples, the study would have been “virtually impossible without the bar codes,” said a key member of the research staff.

WHY BAR CODES?

The use of bar codes has proliferated because it is both fast and accurate (see Table 1). While not the only method of data collection available, bar codes don’t necessitate a trade-off between speed and accuracy. Equally important is the ease of use. Add to that the performance increases and cost decreases of microprocessors, and the rationale for bar-code technology becomes compelling. Bar codes are fast, accurate, easy-to-use, and inexpensive.

BREAKING DOWN BAR CODES

While bar codes have been a part of our lives for years, not everyone understands the technology. Bar-code scanning is based on a simple principle — light is reflected in different amounts by different colored surfaces. To decode the information in a bar code, a small spot of light is passed over the bars and spaces via a scanning device. This bar-code scanner can be a hand-held wand, a fixed-beam device, or a moving-beam device. The bar code will reflect the spot of light back into the scanner in varying amounts. That is, the dark bars of the bar code will absorb light, while the white spaces will reflect light. These differences in reflectivity are translated into electrical signals by a light detector inside the scanner. The signals are converted into binary ones and zeros; these are used in various combinations to stand for specific numbers and letters.

To be an educated consumer of bar-code technology, it’s important to know some commonly used terms to identify important features of the bar code itself (Figure 1).

The quiet zone: This is the area immediately adjacent to the beginning and the end of the bar code symbol. These zones define the parameters of the code. They are not merely aesthetic, but are required for the scanner to determine background reflectance, which enables the device to differentiate between bars and spaces.

Start and stop characters: Found at the beginning and end of each bar-code symbol, these characters tell the scanner from which direction information is being received and which symbology is being used. These characters also provide for “bi-directional scanning,” which means that both left-to-right and right-to-left scan patterns will result in identical decodes.

Check character: Usually the next-to-last character in a bar-code message, this character derives its value from an algorithm that runs on the other characters in the message. The check character ensures the entire message has been decoded correctly.

Interpretation line: This is the line above, beneath, or adjacent to a bar-code symbol where human-readable information appears. It may not exactly match the data encoded; there is no “rule” about what information must appear in the eye-readable unless there is a specification that outlines such a requirement.

PRINTING BAR CODES

Beyond the decision to implement a bar-code identification system, selecting the right label or printing method for bar-code labels is equally important. In the case of the AIDS project, the bar-code labels needed to withstand extreme temperature variances as samples go through five freeze/thaw cycles, going from -70 °C to room temperature and back again. It is imperative that the bar-code labels are read correctly every time, stay adhered to the sample container, and can endure harsh chemicals or extreme temperatures in order to survive in the end-use environment.

Bar-code symbols can either be provided on preprinted labels or printed on-demand. There are advantages and disadvantages to each approach. Some users go through a formal “make vs. buy” exercise to determine the best option for their application.

Pre-printed labels: Microwell plates, glass or plastic vials, slides, and other lab containers can be pre-labeled for maximum convenience. The data required can be printed and/or encoded on the item to exactly meet specifications. Guarantees are available that preclude duplicate numbers and ensure sequence integrity.

On-demand: The most common on-demand barcode label printing technology in the lab is thermal transfer. Printers of this type produce images on label stock by selectively heating or not heating tiny sections of a thermally sensitive ribbon passing over the print head. When the heat element (called a “pixe”) is turned on, the heat it generates causes the ribbon to transfer its image to the label stock moving beneath it. Each of these tiny heaters is controlled by logic in the printer and is a rectangular dot or bar shape. The same printer logic that controls the heating elements also controls the movement of the label stock past the printhead, permitting the printing of a complete label.

There is a wide variety of label stocks available for thermal transfer printers. Many of the non-paper materials (polyester, polyolefin, etc.) will withstand chemical spills and other harsh conditions they might encounter in a lab environment. That means bar-code labels can be used in a lab without concerns about durability and long-term scannability.

Below are some of the features of thermal transfer printers important to labs in making product selections. There are many makes and models available from low-cost desktop units for under $1000 to more feature-rich and costly models.

• Maximum print width—The widest image that can be printed.
• Maximum label width—The widest label stock that can be accommodated.
• Maximum roll size—The outside diameter of the largest roll of label stock the printer can handle. The larger the roll of stock, the less often the roll must be replaced. This can be an important issue for high-volume printing, but is not as critical for medium- and low-volume applications.
• Maximum print speed—How fast the label is printed.
• Rewind and dispense mode—Internal rewind means that the printer will do batch printing and then wind the printed stock onto a take-up roll insider the printer. A more common use of ondemand printers in health care is the print-anddispense mode, in which the label is printed and partially ejected from the front of the printer as the release liner is wound up inside the printer for later disposal.
• Resolution—Measured in dots per inch (dpi), this is the feature that determines the bar code densities that can be printed. Printers used in healthcare are typically 203 dpi, 300 dpi, or 600 dpi. The higher the resolution — the more dots per inch — the smaller the narrow elements that can be printed. Beyond bar-code density, another reason to use a high-density printer is enhanced readability of smaller text.

WHAT’S NEXT IN AUTO ID FOR LAB AUTOMATION?

Bar codes are not the only method of automated data collection. While they have advantages over, for example, to Optical Character Recognition and manual data entry, linear bar codes have inherent limitations that other, newer technologies do not have. While technology is changing at an ever-increasing rate, the following summary highlights the major identification technologies that may replace or enhance the scanning of a simple bar code.

Stacked bar codes are a series of linear bar codes stacked directly on top of one another that form one continuous message. Advantages include higher capacity than linear codes, read by conventional laser scanners, error detection/correction in most symbologies, and printed similar to linear.

Matrix codes are made up of a block of cells that are filled or unfilled to represent binary data, generally arranged on a square grid. Advantages with matrix codes include large data capacity, well-founded optical technology, error detection/correction, and printed similar to linear. Disadvantages include they must be read by image processors (2-D array of CCD sensors), read-only.

While many of these newer technologies offer great promise, the standard against which they all must be measured is the simple linear bar code — the easiest and most cost-effective method for automated data collection available today.

Note: The table and figure are from Roger Palmer’s “The Bar Code Book” (4th Edition), Helmers Publishing Company, Peterborough, New Hampshire, 2001.

Bruce Wray is Marketing Manager of Computype, a global leader in labware identification based in St. Paul, MN. He can be reached at 800-328-0852; bruce.wray@computype.com.