By George Wright IV, Product identification & Processing Systems, Inc.
The International Organization for Standardization (ISO) published a revised specification (ISO/IEC 24724:2011) in April 2011, that redefines the symbol structure, decode algorithm, and scanner processing requirements for GS1 DataBar Limited.
Pharmaceutical labelers who print this symbology on unit-dose and unit-of-use vial, ampoule, or syringe labels; blister packs; cup lids; or other packaging—and the supply chain customers who scan these packages—are affected.
GS1 DataBar Limited is the only member of the GS1 DataBar symbology family to have had a change to its structure. The right guard pattern was redefined to add a trailing 5X wide space element. This modification increases the overall symbol width from 74 modules wide (74X) to 79X, (where “X” is the width of one narrow bar or space element); it also changes the printing, decoding, and verification requirements for this version of the GS1 DataBar family of symbologies.
The symbol structure and printing requirements for all other versions of the GS1 DataBar family—in particular GS1 DataBar Stacked, which is also widely used on pharmaceutical unit-dose packaging—remain unchanged.
The fundamental impact on pharmaceutical manufacturers and other labelers is this: GS1 DataBar Limited must now be printed with a 5X wide “clear area” (effectively, a “quiet zone”) to the right of the final 1X bar. This change must be taken into account by label designers; those who generate GS1 DataBar Limited digital bar code images, particularly EPS format files for label art (including flexographic printing plate suppliers); and any company or organization that prints, verifies, and/or scans GS1 DataBar Limited.
|Figure 1. GS1 DataBar Limited without and with 5X right clear margin and GS1 DataBar Stacked.|
Figure 1 is an illustration of three variations of a layout encoding NDC in GS1 DataBar Limited and Stacked in accordance with FDA regulations. The symbol in the top design was perfectly satisfactory under the original symbology specification and would have received a high ISO/IEC print quality grade. However, it does not meet the new 5X clear area requirement. For this reason, the symbol may now receive an “F” print quality grade. Moreover, it may not scan in the supply chain (e.g., in pharmacies or at the point of care) when scanned with scanners that have updated GS1 DataBar Limited decode algorithms conforming to the new specification.
The middle design represents the same blister/label but with the GS1 DataBar Limited symbol reduced by 10% and offset slightly to the left. The symbol in this layout, with at least a 5X clear area, meets the new specification and should receive a high grade. It should also be readily decoded by any scanner equipped to scan GS1 DataBar Limited, no matter what the decode algorithm.
The bottom design incorporates a GS1 DataBar Stacked symbol instead of Limited. This symbol is narrower and slightly taller than Limited and should receive a high print quality grade. Guidance on when to reduce the size of a GS1 DataBar Limited symbol versus change to the GS1 DataBar Stacked format is offered below.
The changes to the symbology standard were not incorporated into the current edition of the GS1 General Specifications, Version 12 Issue 1, published January 2012. However, they were developed in close cooperation with GS1 Global Office and are expected to be reflected in the 2013 edition, according to GS1. In any case, when it comes to the encoding and decoding algorithms of a symbology, ISO/IEC standards take precedence over GS1 specifications.
UPC-A and GS1 DataBar Limited
This specification update was brought about because in laboratory tests, scanners reading 12-digit UPC-A symbols sometimes transmitted data as if they had read a GS1 DataBar symbol. That is, instead of transmitting the EAN/UPC symbology identifier “]E0” followed by a 12-digit Global Trade Item Number (UPC code), the scanner transmitted the GS1 DataBar family symbology identifier “]e0” followed by GS1 Application Identifier “01” (as specified) and a totally unrelated 14-digit GTIN as would be encoded in GS1 DataBar symbology.
Further investigation revealed that a valid GS1 DataBar Limited symbol pattern exists in the interior of some UPC-A symbols. Thus, under certain rare circumstances a scanner will instead “see” a valid GS1 DataBar Limited pattern and decode it. This has been referred to as a UPC-A “short-scan.”
|Figure 2. GS1 DataBar Limited “embedded” in UPC-A|
The result is a misread, where a valid (but incorrect) GTIN-14 message, in what the scanner “sees” as a GS1 DataBar Limited symbol, will be decoded instead of the intended GTIN-12 message encoded in the UPC-A symbol. Figure 2, which illustrates these similarities, is substantially identical to Figure H.2 “All problematic UPC-A cases (09, 07, 04, and 02)” in the revised specification.
This short-scan scenario can occur only if GS1 DataBar Limited symbology is enabled (“turned on”) in a scanner and, in addition, only if the symbol being scanned is one of the tiny fraction of UPC-A symbols that can misread under these conditions. Fortunately, this subset of “problematic” UPC-A symbols is either reserved for “closed loop” systems or otherwise
restricted and is not used in the global healthcare supply chain.
As one can see from the four UPC-A bar/space patterns directly below the blue GS1 DataBar Limited symbol in Figure 2, there is no difference in the interior patterns between these examples. The only difference (at most) is in the left-most UPC-A space/bar pattern (looking right to left) directly beneath the upside-down “3” in the GS1 DataBar Limited human-readable interpretation (top left). This space/bar pattern corresponds to the original GS1 DataBar Limited right guard pattern (which, because the GS1 DataBar Limited symbol is upside down, appears on the left). So, for all intents and purposes, these four UPC-A symbols are “identical” to the GS1 DataBar Limited symbol and will misread.
The new decode algorithm now includes measurements and analysis of the left and right ends of the symbol in order to prevent exactly this kind of misread.
Potentially Disruptive, Not Alarming
The phenomenon of a misread within most any linear bar code is widely understood by experts. With literally billions of scans around the globe every day, such misreads occur regularly, whether the symbology is EAN/UPC, Code 128, GS1 DataBar, or some other symbology.
With respect to UPC-A and GS1 DataBar Limited, according to the revised specification, a misread due to a UPC-A “short-scan” will occur in only 5,329,400 out of a total of 100 billion possible UPC-A symbol patterns. And as noted above, these symbols should never be seen in the healthcare supply chain. Taking all factors into consideration, according to an analysis done for GS1, the theoretical possibility of such a misread on any given UPC-A symbol in the healthcare supply chain is infinitesimal.
Moreover, even if a misread occurs, the GS1 system is predicated on database lookup and an “Item not on file” message should be reported by the system. When this happens the user should be instructed to key in the correct GTIN from the human-readable number below the symbol.
Although there is no cause for alarm, some supply chain disruption will occur in the near term, particularly for unit-dose manufacturers and packagers who have label/blister layouts using GS1 DataBar Limited without the necessary 5X clear area—and also in some healthcare facilities where GS1 DataBar Limited is scanned, particularly those with newer scanners that have the revised GS1 DataBar Limited decode algorithm.
Changes and Implications
The revised GS1 DataBar symbology specification includes changes to address the specific GS1 DataBar Limited design flaw that can cause a scanner to misread a UPC-A symbol as a valid GS1 DataBar Limited symbol (but with a different encoded message). The change is simple but it directly affects GS1 DataBar Limited symbol pre-press artwork, print quality verification, and scanning. Nevertheless, it was deemed the least disruptive and only acceptable means to address the problem short of retiring the symbology.
Historically, none of the GS1 DataBar symbology versions required a clear white area or “quiet zone” following the last bar on the right, which is part of the right-hand guard pattern. For GS1 DataBar Limited, this bar was, and still is, defined as a 1X wide element. However, originally this bar could butt right up against a dark background or, much more commonly on unit-dose
pharmaceuticals, right up to the edge of a “label.” That might be literally the edge of a label on a syringe, vial or ampoule; or the edge of a single hospital unit dose blister cell as shown in the photo in Figure 4.
Under the revised specification the symbol’s right guard pattern has been physically redefined—by the addition of a 5X wide trailing space element following the last bar. Figure 3 (adapted from the new ISO/IEC specification) depicts the new right guard pattern (reading left to right) as “1Xspace/1Xbar/5Xspace.” The left guard pattern remains “1Xspace/1Xbar.” In addition, both the left guard and right guard patterns are now included in the revised decode algorithm. These changes help prevent misreads due to UPC-A short-scans. But they also mean that verifier and scanner decode algorithms have to change to be in conformance.
|Figure 3. GS1 DataBar Limited symbol structure.|
The practical implications for an organization vary but are immediate. Pharmaceutical companies that print GS1 DataBar Limited should promptly examine their unit-dose label layouts to determine if any of them have less than a 5X right hand clear margin. They must update those that do not as soon as practical. This will bring them into conformance with the new spec and eliminate any scanning problems with these packages.
Graphic designers need to be made aware that they must now leave a minimum 5X wide clear space to the right (and 1X to the left, as always). This is important to emphasize because for more than 10 years they have been taught that with GS1 DataBar symbology “no quiet zone is required.” A minimum of 6X on the right and 2X on the left would be this expert’s recommendation.
Digital bar code symbol generation software should be updated by the publisher to make this new 5X space element explicit by moving the “bounding box” out to the right by (at least) 5X. Some 3rd party suppliers of digital bar code masters (and flexo platemakers, for example) are already in conformance with the new specification. Companies should check and see if their software and suppliers are up to date.
|Figure 4. GS1 DataBar Limited without the newly required 5X clear area, but where the symbol can be easily repositioned.|
The addition of a 5X space on the right increases the overall symbol width by approximately 7%. If GS1 DataBar Limited symbols are already being printed virtually to the edge of the label/blister and cannot be moved to the left a sufficient amount, then either the X-dimension of the Limited symbol will have to be reduced or the labeler will have to change to GS1 DataBar Stacked, which is much narrower, even at the same X-dimension (and which may still be printed with no clear margin or “quiet zone”).
However, put simply, reducing the X-dimension reduces the ease of printing to a high print quality grade and also may reduce a symbol’s overall “scannability.” If the original GS1 DataBar Limited X-dimension is already at or below 10 mils (0.010 in.) then it may be better to use a GS1 DataBar Stacked symbol instead. The Stacked symbol is only 50X wide, and can therefore be printed at an even higher X-dimension (say 12 mils) than the original Limited symbol it replaces. However, the Stacked symbol version is 13X tall, whereas the Limited version is only 10X tall. If the label format cannot tolerate the additional height, then a Limited symbol with a reduced X-dimension will have to be used.
Bar code print quality verifier software also has to be updated and at least one leading manufacturer has already made the change. Because the new reference decode algorithm now includes the left and right guard patterns—and the new right guard pattern has a 5X trailing space that was not previously defined—updated verifiers that strictly conform to the new specification will, quite properly, fail any symbol printed without the minimum required clear area left (1X, as before) and right (now 5X).
On the other hand, verifiers that are not updated with the new algorithm will erroneously “pass” non-conforming (“failing”) symbols. Thus, they will not accurately predict the scannability—likely poor to none when scanned with scanners that use the new algorithm—of symbols lacking the 5X minimum right-hand clear margin.
This brings us to the question of what is going to happen in healthcare facilities when unit-dose/unit-of use packages are scanned. Scanners that do not incorporate the new GS1 DataBar Limited decode algorithm will continue to readily scan Limited symbols (subject to print quality, as always) with or without a 5X clear margin. But, they will remain susceptible to misreads due to UPC-A short-scans. Users will have to judge whether the real-world likelihood of these rare misread events justifies upgrading their scanners or not.
Scanners that have the new GS1 DataBar Limited decode algorithm—and some scanner manufacturers have already incorporated the change—will probably not decode GS1 DataBar Limited symbols that do not have the 5X clear right margin. And a small but unknown percentage of all bar coded unit-dose packages now in the supply chain were designed and printed this way, that is, printed without the 5X clear right margin. For the ever increasing number of users scanners with the new GS1 DataBar Limited decode algorithm, this probably means that they will suffer some disruption in scanning unit-dose medications over the next 2–3 years (a typical shelf life for many unit-dose drugs) as these medications work their way through the supply chain.
It is impossible to predict what the extent of the disruption may be or what, if anything, might be done to mitigate the inconvenience. Certainly there are 2-3 mL vial and ampoule labels and small blister cells that use GS1 DataBar Limited printed with less than a 5X clear area between the right-most bar and the edge of the label. Even some larger packages with ample room to properly position a Limited (as shown in the photograph in Figure 4) are not in conformance.
Whatever the extent, it is the general consensus among the experts involved in addressing this problem (including those at GS1), that the chosen approach is the least disruptive to users of the GS1 system.
Pharma manufacturers need to be aware that these changes are going to result in some disruption in pharmacies and at the point of care. Manufacturers should alert their sales support and customer service teams to the potential for this disruption and be alert to customer feedback.
George Wright IV is Vice-President, Consulting & Business Development, at Product Identification & Processing Systems Inc. (PIPS). He is Vice-Chair of the AIM Unique Device Identification (UDI) Committee, Past Chair of the AIM Technical Symbology Committee (TSC); a certified GS1-US Bar Code Consultant and a regular contributor to Pharmaceutical & Medical Packaging News. Questions, comments or requests for implementation assistance may be emailed to the author at firstname.lastname@example.org.