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Your attention please... Designing effective warnings

From the August 24, 2006 issue

Medication-related warnings are often employed to reduce the risk of accidents and injuries. Warnings help to inform staff about safety issues confronting them and attempt to influence staff behavior in ways intended to improve safety. While warnings can play an important role in safety, their design and use are no simple matter. To be effective, warnings must reach their target audience, capture their attention, and cause the recipient to understand, agree with the warning, and respond accordingly.

Over the past few decades, a sizable body of research has been amassed about warnings. A leading international authority on warning design and use, Michael S. Wogalter, has compiled many of the important contributions to this field of research in his latest book, Handbook of Warnings (Wogalter MS ed. Handbook of Warnings. Lawrence Erlbaum Associates: Mahwah, NJ; 2006). Some of the conclusions drawn by Wogalter’s contributing experts and editorial advisory board are provided below as examples of ways we can improve the design and delivery of medication-related warnings–from black box warnings and “Dear Doctor” letters to auxiliary medication labels and electronic warnings.

Target audience. Consider the target audience and design the warning in a way that takes into account the lowest level of ability, training, and experience of staff who may encounter the warning.  

Message detail. The warning has value only if the receiver can readily use it to improve his or her performance. Thus, explicit and detailed warnings that include desired actions and consequences of noncompliance improve understanding and effectiveness. If an inference must be made, the warning may not be fully comprehended or may be dismissed by busy staff.

Source credibility. Staff will pay more attention to warnings that stem from expert and trusted sources, and if the consequences are easily imaginable or salient. If the communication appears legitimate and free of a conflict of interest, believability is enhanced and compliance is improved.

Font size and format. Larger size fonts that are not densely compressed are easier to read, although under certain conditions, closer spaced type can increase reading speed. For example, information printed in a 7- or 10-point font will be read by more of the target audience than information in a 4-point font. Small medication labels are particularly problematic in this regard, but adequate space can be provided through special extended labels if necessary. White spacing between label sections enhances readability. If the warning includes distinct components, presentation in a list is more effective than in paragraph style.

Font style. Familiar sans serif fonts without embellishment, such as Helvetica, Arial, and Univers, are preferred for warning messages over fonts with serifs (short decorative line at the start or finish of a stroke in a letter) such as Times New Roman, New Century Schoolbook, and Goudy. Serif fonts are preferred when the font size is small, as it tends to be less fatiguing than sans serif fonts. However, the presence or absence of serifs does not have a substantial effect assuming the font style is not extremely elaborate or unusual.

Letter case. Warnings are best presented in mixed case letters, which are read more easily than all uppercase letters. Block-like uppercase letters look similar, especially in low lighting; lowercase letters are more unique and distinguishable. 

Signal words and background color. Use a red background with white lettering for danger, orange background with black lettering for warning, and yellow background with black lettering for caution to indicate decreasing levels of hazard. Danger conveys greater hazard than caution and warning and should be reserved for the most extreme cases. Most people find little distinction between caution and warning, or between orange and yellow, the colors used to signal caution and warning. Other signal words that have been tested for effectiveness include the following in descending order of hazard: Deadly, Fatal, Poison, Danger, Hazard, Vital, Severe, Serious, Urgent, Beware, Warning, Harmful, Caution, Alarm, Alert, Careful, Prevent, Needed, Notice, and Note. Signal words can also be used in auditory warnings, eliciting a response similar to visual signals.

Colors of print. Warnings printed in distinct colors are more noticeable than those printed in black.

Symbols. Warnings are identified more quickly if they include symbols or pictures that are bold, have high contrast, are simple in form, and closely represent the intended message (e.g., Mr. Yuk, skull-and-crossbones, circle with a slash through it [as long as the slash mark does not obscure the critical elements of the symbol]). 

Text and symbols. Use of conspicuous text (larger font, color highlights) along with pictures or symbols enhances comprehension and recall. For example, medication instructions are recalled more easily when warnings include redundant text and pictures. Training to associate symbols or pictures with the related written warning dramatically improves comprehension and memory of warning symbols or pictures. 

Placement of warning. Optimally, the warning should be attached directly to the product. For very small products that will not allow this, the warning should be located in an area where users will most likely interact with it when using the product. The most noticeable and effective warnings are placed in such a way that the task is temporarily interrupted and the receiver must physically interact with it to continue. Warnings placed before instructions result in higher compliance than warnings placed after instructions.

Situational cues. Warnings should be integrated into the task where the hazard might occur so they happen during the most relevant times.
Academic detailing. For healthcare providers, particularly physicians, the distribution of specific warning information combined with face-to-face educational programs (sponsored by professional organizations or healthcare providers, not the manufacturer) about the hazard improves compliance with the warning and desired actions. Distribution of printed material alone will not substantially alter behavior.

Clinical importance. Thresholds for warnings must be set appropriately to be effective. False alarms or clinically insignificant warnings will cause rational staff to ignore the warning completely (and other warnings, too). Indiscriminate use of warnings can also lead to “alert fatigue,” which could lessen the effectiveness of all warnings. The most effective warnings will employ different thresholds based on the receivers’ expertise and performance. 

Modes of delivery. When presenting short warning messages, auditory channels are more effective than visual channels. When presenting long and complex warnings, visual modes of delivery are most effective. However, use of multiple modes of delivery promotes the highest level of attention, comprehension, and compliance with warnings. The use of less traditional modes of communication such as touch and smell can also improve compliance. 

Although warnings offer a valuable strategy for providing important safety information, there are limitations on what can be accomplished. At best, warnings are a lower level of defense in the sequence of preferred safety strategies. They supplement, but are no substitute for, safe process design and high-leverage strategies that guard against error. However, as we learn to design more effective human-centered warnings, there’s no doubt that they will help us interact with our environment more safely and reduce error rates. The vast amount of information provided in more than 800 pages of the Handbook of Warnings will serve as an essential resource for this endeavor.

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