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Drug Labels Spell Trouble for Patients


SHREVEPORT, La. -- When shown the instructions on five common prescriptions, only a third of mostly low-income patients of mixed literacy understood how to carry them out.

SHREVEPORT, La., Nov. 30 -- Even well-read patients may have trouble deciphering and carrying out instructions on prescription medicine labels, which could spell trouble, researchers here warned.

When shown the instructions on packages for five common prescriptions, more than two-thirds of mostly low-income patients of mixed literacy could read the wording, but only one-third knew what to do next, reported Terry C. Davis. Ph.D., of Louisiana State University Health Science Center here, and colleagues, in the Dec. 19 issue of Annals of Internal Medicine.

Dr. Davis also presented the results of the study at a meeting of the American College of Physicians Foundation in Washington.

And while patients with low or marginal literacy made the most mistakes, even those patients with the highest literacy levels erred from 5% to 27% of the time, the investigators reported.

"We came at this from a health literacy perspective, but we found it was a problem with many people in general," said coauthor Michael S. Wolf, Ph.D., M.P.H., director of Northwestern's Health Literacy and Learning Program, in Chicago. "It was surprising how prevalent mistakes were regardless of an individual's literacy level. Just being able to read the label doesn't mean you'll be able to interpret it."

According to a 2006 Institute of Medicine report, an estimated 1.5 million people in the United States are harmed by preventable drug errors each year, and treatment of drug-related injuries adds at least .5 billion annually to the nation's health care bill, not counting indirect costs such as lost income and ancillary health and home care services.

In an editorial accompanying the current study, Dean Schillinger, M.D., of the University of California at San Francisco wrote that "although the authors did not assess actual medication-taking behaviors, other research has found that misunderstanding one's own warfarin prescription label, as measured by a similar test, is associated with limited literacy and unsafe anticoagulant outcomes, providing support for Davis and colleagues' conclusion that low literacy can have clinical consequences."

To assess how well patients with varying literacy levels could understand and demonstrate instruction on common prescription labels, the authors approached patients in clinics serving mostly low-income patients in Shreveport, Chicago, and Jackson, Mich.

They recruited 395 English-speaking adults who were waiting to see their providers and showed them labels for five common medications: pediatric amoxicillin, trimethoprim, guaifenesin, felodipine; and furosemide.

The investigators then asked the volunteers "How would you take this medicine?" and recorded the verbatim responses, which were then rated for accuracy by three general medicine physicians from three separate institutions.

The investigators also checked whether patients understood auxiliary instructions such as ""Take with food" or "Do not chew or crush, swallow whole."

Finally, to see whether the patients could translate the written information into action, the patients were asked to demonstrate, using candy pills to count out the dosage, how they would carry out the instruction "Take two tablets by mouth twice daily" for the expectorant guaifenesin.

The volunteers' literacy levels were tested with the Rapid Estimate of Adult Literacy in Medicine test, a 66-word test developed by Dr. Davis and others that correlates with reading levels.

The authors found that the patients understood the labels from 67.1% to 91.1% of the time, and that patients reading at or below the sixth-grade level, who were categorized as having low literacy, were the least able to understand the instructions on all five labels.

"Although 70.7% of patients with low literacy correctly stated the instructions 'Take two tablets by mouth twice daily,' only 34.7% could demonstrate the number of pills to be taken daily," the investigators wrote.

While the inability to count out the right number of pills might be considered to be more of a problem with numbers than a problem with reading, numeracy is considered to be a part of literacy, the authors noted.

"The most common misinterpretation was to take two pills a day," Dr. Wolf said. "It's not that they couldn't figure out two plus two equals four. Rather, it's the way the instructions were written. It's awkward wording."

The investigators determined that the instruction the volunteers found most difficult to grasp was "Take one teaspoon three times a day for seven days."

"It's possible people read this quickly because they perceive it as simple," said Dr. Wolf. "They get the numbers flipped. They confuse and misread them."

After controlling for potential confounding variables such as literacy, age, number of medications taken, gender, and race, the investigators found, low (adjusted relative risk, 2.32 [95% CI, 1.26 to 4.28]) and marginal (adjusted relative risk, 1.94 [CI, 1.14 to 3.27]) literacy were significantly associated with misunderstanding compared with literate volunteers (ninth-grade reading level and above).

They also found that taking a greater number of prescription medications was also statistically significantly associated with misunderstanding (adjusted relative risk, 2.98 [CI, 1.40 to 6.34] for five or more medications).

The authors noted that the study findings were limited by the fact that the sample population was already at high risk for poor health literacy and outcomes. In addition, most of participants were women, and all spoke English, making it difficult to generalize the findings to a larger population.

Nonetheless, their findings suggest that "patients of all ages would benefit from additional efforts to improve the clarity and comprehensibility of labeling on prescription drugs," they wrote.

They called for a redesign and standardization of the text and format of prescription labels to include simpler and more explicit dosing instructions.

"Why don't we have a standardized system to transmit medication instructions that all patients can understand and act on?" Dr. Schilling asked in his editorial.

"Perhaps it is because the field of health literacy is in its infancy and research findings have not yet been translated into policy changes. To date, we have invested too little in generating the scientific evidence to show that one labeling practice or communication system is superior to another. Furthermore, because the framework for regulating the content of prescription labels and accompanying materials is inadequate, patients and clinicians are suffering. With this study, the genie is out of the bottle."

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