Bar codes may have poorer error rates than commonly believed.

By most accounts (1 ), the development of bar code technology is credited to 2 graduate students at Drexel University. In 1948, Bernard Silver had overheard the president of a local grocery chain asking a dean at the University whether they could develop a system to read product information at checkout. Silver told his colleague Norman Woodland of this request. After one failed idea involving ultraviolet light, Woodland, convinced that he could solve this problem, quit his parttime teaching position at Drexel and moved to Florida to live with his grandfather. While walking on the beach one day and with the inspiration of the Morse code, he used sand to extend the dots and dashes of the codes downward in thin and thick lines. Silver and Woodland filed a US patent application on October 20, 1949, entitled “Classifying Apparatus and Method.” The patent, 2 612 994, was issued on October 7, 1952. It described both a bull’s-eye printing pattern of codes as well as a linear pattern similar to that of the bar codes we know today. The initial adoption of bar code technology was slow. Attempts to track railroad cars, vehicles with monthly passes crossing a toll bridge, and US Post Office trucks all had limited success. A trial in which Kal Kan used bar codes to track cases of pet food for inventory control sparked the interest of the grocery industry, and a meeting of the National Association of Food Chains in 1966 discussed the use of automated checkout systems. Progress continued to be slow, but in 1974 the first successful scan of a Universal Product Code (UPC) code on a package of chewing gum at a grocery store in Troy, Ohio, ushered in the bar code era (1 ). Today, more than 2 dozen different linear bar code symbologies are in use, as well as a number of 2-dimensional coding systems. For the most part, these different codes have applications in different industries. In clinical laboratories, the codes most frequently used have been Code 39, Interleaved 2 of 5, and Code 128. CLSI standard AUTO02-A2 has specified Code 128 for sample labels for use in laboratory automation systems (2 ). Code 128 is also specified by the American Association of Blood Banks for use by blood banks in blood component labeling (3 ). Most of us working in the clinical laboratory industry understand that bar codes are far more accurate as a means of data entry than human keystrokes and that data are entered into the computer record much more quickly (4 ). For example, the entry of 12 characters with keystrokes may take 6 s, whereas reading a bar code of the same 12 characters may take 1 s. Furthermore, the error rate for keystroke data entry is generally stated to be 1 substitution per 300 characters, whereas bar codes, depending on the symbology used, have much lower error rates (4 ). A few examples of error ranges for different bar code symbologies are: UPC, 1:394 000 (worst case) to 1:800 000 (best case); Code 39, 1:1.7 10 to 1:4.5 10; Code 128, 1:2.8 10 to 1:37 10) (5 ). In this issue of Clinical Chemistry, Snyder and colleagues (5 ) report an unexpectedly high error rate of 1:84 000 with Code 128 on patient wristbands scanned with several bar code readers in point-of-care devices. The bar-coded patient identifiers were each 12 digits. Over the course of a full year, the authors observed a total of 10 substitutions of 1 or more characters for the correct characters out of 840 000 scanned wristbands. This rate is 15 times higher than the poorest error rate described for Code 128 and 440 times higher than the best-case error rate for that symbology (4 ). The authors describe the rates of the observed incidences, in which various bar code readers substituted incorrect digits, “converted” Code 128 symbology to a different symbology (leading to completely incorrect identifiers that were rejected), or simply failed to read the encoded identifier on the patient wristband, again causing rejections. The rejections did not pose a potential for patient harm because the error was immediately noticed and the correct identifier was entered into the record; however, the substitution errors in which 1 or more incorrect characters replaced correct characters produced identifiers that appeared correct in format, but that had the potential to cause patient harm if not caught and corrected. In their investigation into the problem, Snyder and colleagues compared “pristine” bar codes printed by the printer vendors to bar codes printed on different 1 ARUP Laboratories, Salt Lake City, UT; 2 Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT. * Address correspondence to the author at: ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT 84108. Fax 801-584-5207; email [email protected]. Received July 20, 2010; accepted July 22, 2010. Previously published online at DOI: 10.1373/clinchem.2010.153288 Clinical Chemistry 56:1