Misidentification of Alphanumeric Symbols in Electronic Communications

Pharmacy TimesFebruary 2016 Autoimmune Disorders
Volume 82
Issue 2

Problems may arise during electronic communication because of similarities in appearance among the alphanumeric symbols we use.

The English language uses the Latin alphabet with 26 letters and a numeric system with 10 numerals. These alphanumeric symbols work well, most of the time, when used to communicate information. However, problems may arise during electronic communication because of similarities in appearance among the alphanumeric symbols we use.

For example, a clearly typed prescription for 25 mcg of LEVOXYL (levothyroxine) could be misread as 125 mcg if it appears without proper spacing as, “Levoxyl25 mcg,” especially since both strengths are available for this medication. To cite another example, those familiar with computer-generated passwords know how easy it is to misidentify a lowercase letter l in a password (or e-mail address) as the numeral 1, or the letter O as a numeral 0. Information that contains both numerals and letters—including a medication order—is particularly prone to errors.

The probability of confusing one alphanumeric symbol with another largely depends on the number of distinguishing factors between the look-alike pair. The fewer the distinguishing factors, the greater the risk of confusion. For example, the letter O and numeral 0 are at high risk for confusion because there are no discernable factors between them.

While context can sometimes enhance symbol recognition, it can also detract from recognition. For example, if you saw Z, I, or O amid an array of numerals, you could easily mistake the symbols as the numerals 2, 1, or 0. Also, word recognition software often has difficulty distinguishing between L and I, Z and 2, and other look-alike symbols. In fact, research conducted by Bell Laboratories found that some alphanumeric symbols are more vulnerable than others to misidentification.1 The symbols l and 1, O and 0, Z and 2, and 1 and 7 accounted for more than half of the errors caused by symbol misidentification in the study.

Safe Practice Recommendations

The characteristics of alphanumeric symbols that form each word or number determine the accuracy and speed at which material may be read or identified. Clarity regarding the following 3 characteristics allows readers to focus on the message, instead of the mechanics of reading2:

  • Visibility: the quality of an alphanumeric symbol that makes it separately discernable from its surroundings
  • Legibility: the attribute of an alphanumeric symbol that makes it possible for each character to be recognized
  • Readability: the quality that enables the recognition of the informational content of the material

Use Lowercase or Mixed-Case Letters

Avoid using all uppercase letters. The brain recognizes written words by the shape of the word.3 When using all uppercase letters, a word’s shape is not offered as a visual clue to aid in word recognition.3 Words in all uppercase letters may serve a small role for emphasis.

Be Selective About Font

Sans Serif fonts are easier to read on computers, although a Roman-style Serif font is easier to read in print.3 The Roman-style Serif font is widely used, legible, and provides high discrimination between alphanumeric characters; but, Serif fonts, more elaborate than this style, should not be used.2

Avoid Italics and Underlining

Italics and underlining should be avoided, as they make it more difficult for readers to recognize a word’s shape. However, italics for words or clauses may be used according to publishing guidelines (eg, Latin terms, journal titles, bacteria nomenclature).

Ensure Proper Spacing

Allow proper space between the individual letters of a drug name and between the drug name and the dose (eg, Inderal 20 mg) on all printed prescriptions, preprinted order sets, and electronic formats such as computer screens, computer-generated medication labels and medication administration records, and shelf labels.

Dr. Gaunt is a medication safety analyst and the editor of ISMP Medication Safety Alert! Community/ Ambulatory Care Edition.


  • Nierenberg GI. Do It Right the First Time. New York, NY: John Wiley and Sons; 1996:154-162.
  • Kelly MJ. Preliminary human factors guidelines for traffic management centers. Electronic Systems Laboratory, for US Federal Highway Administration; 1999.
  • Oberoi A. How typography affects readers. Adpushup. adpushup.com/blog/how-typography-affects-readers. Published December 6 2013. Accessed January 4, 2016.

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