Anticoagulant Patient Information Material Is Written at High Readability Levels

Warfarin is indicated in elderly persons with atrial fibrillation to prevent stroke, and its use requires frequent monitoring and dose adjustments. Patient education is important when drugs with a narrow therapeutic index, such as warfarin and low-molecular-weight-heparins (LMWH), are prescribed. Patients who take anticoagulants need to understand the risks and benefits of the medications, the need for regular blood tests, when to contact the physician, when to seek immediate medical attention, the importance of compliance, and the potential for medication interactions. To accomplish these goals, patients are instructed verbally, or with videos, or by use of written information.

Written communication is efficient and is the least costly method to inform and instruct patients. However, available material is often written at levels beyond the patient’s literacy level.¹²³⁴ Literacy is defined as the ability to use printed and written information to function in society, to achieve one’s goals, and to develop one’s knowledge and potential.⁵ A 1992 survey estimated that 21% of the adult population in the United States had only rudimentary reading and writing skills.⁵ Among elderly patients, the prevalence of inadequate literacy increased with age (15.6% for ages 60 to 65 and 58% for ages >85).⁶ In the health care setting, health literacy is defined as the ability to perform basic reading and numerical tasks required to function in the health care environment.²⁷ People in the lowest literacy level have difficulty reading and understanding material written at the 6th-grade level. Persons with marginal literacy levels have difficulty reading and understanding material written at the 10th-grade level. Finally, persons with adequate literacy levels comprehend most material written for health care purposes (above 10th-grade level).⁶

The impact of literacy on health is significant.² Adults with low literacy skills have a poorer health status,⁸ have average health costs that are 6 times higher,⁹ are less likely to comply with medication regimens, and are less likely to understand their illnesses. For example, patients who have the human immunodeficiency virus and who are at the lowest literacy level are 4 times less likely to adhere to antiretroviral regimens.¹⁰ Fewer patients with hypertension who were at the lowest literacy level knew that a blood pressure >160/100 was high (55%, compared with 92% of those with higher literacy levels). Also, fewer patients with diabetes at the lowest reading level knew the symptoms of hypoglycemia (50%, compared with 94% of those with higher literacy levels).⁷ Clinicians need to be sensitive to the fact that low literacy, or associated factors, may impact clinical interventions, compliance, or outcomes.

Elderly patients are at a greater risk for not following directions because of lower literacy levels, greater numbers of prescriptions, more prevalent cognitive impairment, and higher rates of stroke. Therefore, appropriate low literacy educational material for patients is necessary. Whether teaching material for patients on anticoagulants is written at a low reading level or not is unknown. Our objective was to determine the readability of patient information material offered to patients receiving anticoagulants.

Subjects and Methods

We obtained printed patient information regarding the use of anticoagulants from manufacturers of warfarin and LMWH, health advocacy groups (American Heart Association, National Stroke Association), the United States Pharmacopoeia, and others. We also obtained information posted on the Internet. Anticoagulation management units commonly use patient information reviewed in this report. We excluded information written in languages other than English and information written specifically for health care professionals.

Readability of written information was measured using the SMOG grade formula¹¹ (SMOG is not an acronym). We chose the SMOG formula because it is accurate and correlates highly with other readability formulas (FOG, 0.99; Fry, 0.93).¹² The SMOG, recommended by the American Cancer Society,¹³ is simple, easy to use,¹²¹⁴ and is widely used in health literacy studies.¹⁵¹⁶¹⁷ Briefly, the method consists of first selecting 3 groups of 10 consecutive sentences at the beginning, middle, and end of the document, for a total of 30 sentences. Then, all words with 3 or more syllables within those sentences are tallied and added together. Next, the square root of that total is obtained and its integer calculated. The number 3 is added to the integer to obtain the grade level of the document.¹¹ A modified formula was used to assess the grade level for brochures with <30 sentences.¹⁸ The test-retest reliability among 15 randomly selected brochures showed a grade level difference of 0.2 (SD 1.4); 73.3% of grades were the same or were within 1 grade level.

The Flesch-Kincaid Grade Level formula was also used to determine readability. The Flesch-Kincaid is appealing because of its availability in commercial word processing software (Microsoft Word 7.0, Microsoft Corp). The formula utilized in the software is [(0.39×ASL)+(11.8×ASW)−15.59], where ASL is the average sentence length (number of words divided by number of sentences) and ASW is the average syllables per word (number of syllables divided by number of words).¹⁹

We used ANOVA to compare means and the Pearson correlation coefficient to assess the relationship between the 2 methods of determining readability. The level of significance was set at P<0.05.

Results

We examined 50 brochures: 8 (16%) dealing with atrial fibrillation, 22 (44%) concerning the use of warfarin, 6 (12%) discussing the use of LMWH, and 14 (28%) related to other themes (Tables 1 through 4). Eighteen brochures (36%) were produced by health advocacy groups and 32 (64%) by private industry. We found 9 brochures (18%) on the Internet. Eighteen brochures (36%) contained fewer than 30 sentences.

The mean SMOG readability grade level was 10.7 (95% CI 10.1 to 11.2); 12% of the brochures had readability scores at the 7th- to 8th-grade levels, 74% at the 9th- to 12th-grade levels and 14% at higher than 12th-grade level (Table 5). The SMOG readability grade level was similar for brochures produced by health advocacy groups (10.7 grade) and private industry (10.6 grade; P=0.9). Readability levels were higher for information obtained from the Internet (12.2±1.3 grades) compared with other patient information materials (10.3±2.1 grades; P=0.01).

The readability level was the same for brochures containing >30 sentences compared with shorter brochures (P=0.9). The readability grade was similar for brochures related to atrial fibrillation (10.6 grade), to the use of warfarin (10.9 grade), to the use of LMWH (10.4 grade), or to other themes (10.4 grade; P=0.8).

For the same brochures, the Flesch-Kincaid mean readability grade was 8.8 (95% CI 8.3 to 9.4; Table 5). The mean grade level as determined by the Flesch-Kincaid formula was 1.8 lower than the SMOG grade level (95% CI 1.4 to 2.3). The correlation between the Flesch-Kincaid and the SMOG was 0.69 (P<0.001).

Discussion

We found that most written patient information material (88%) regarding the use of anticoagulants is written at the 9th-grade educational level or higher. We used an accepted method to determine document readability, the SMOG grade level.¹²¹³¹⁴ Similar findings have been shown in other areas of medicine. Patient information was written at the 8th- to 10th-grade levels or beyond in brochures regarding smoking cessation,¹⁴ asthma,²⁰ diabetes,²¹ cancer,¹³ and informed consent.²² The high readability levels did not differ among shorter and longer brochures, according to the theme discussed, or with regard to the source of the information. As expected, patient information material available on the Internet had higher readability levels.

The readability level of patient information material contrasts with the observed patients’ abilities to read. One third to one half of English speaking patients have difficulty reading material at the 10th-grade level.⁶²³ The estimates are greater among older patients at urban public hospitals (81%)⁷ and among Spanish-speaking patients (54% to 83%).⁶⁷ Another compounding problem is that a patient’s educational level does not automatically guarantee proficiency at that same level. Patients’ observed reading abilities are usually 3 to 5 grade levels below what they report as grade completed. For example, among patients receiving warfarin at an anticoagulation management unit, 53% could not read material written at the 9th-grade level, while 83% of them reported having completed the 9th grade or beyond.²⁴ Tailoring readability of patient information to reported grade completed may result in inappropriate material.

The Flesch-Kincaid formula may seem an attractive method to determine readability, because it is available in commercial word processing software. However, it provides lower estimates of readability. In other studies, the Flesch-Kincaid formula yielded estimates of 0.9 to 3.2 grades lower than standard readability formulas.³²⁵ We recommend that the Flesch-Kincaid formula not be used to determine readability of printed information.

Patients taking anticoagulants who are at risk for bleeding and thrombosis need to learn and understand their condition. As increasing numbers elderly patients with atrial fibrillation receive warfarin, the need for more efficient and effective ways to communicate with them will increase. Patient information should be written at an appropriate reading level, and its readability could be determined by using the SMOG formula. The National Work Group on Literacy and Health recommends that material be written at or below the 6th-grade level,¹²⁶ because material written at higher levels is less likely to be read or understood. Developing patient information at a low readability level is necessary but not sufficient to improve comprehension. Other methods of communication, and written information that uses figures, pictograms, large font, and other characteristics, may also improve comprehension.²⁷ Future directions should include the development and testing of patient information materials written at a low reading level.

In summary, patient information material regarding the use of anticoagulants is written at levels beyond the comprehension of most patients. The individual readability levels displayed in Tables 1 through 4 could be used when determining the most appropriate materials for patients, but none meet the recommendation for 6th-grade level or below.

Appendix A1

Sources of Patient Education Material †United States Pharmacopeial Convention, Inc. Complete Drug Reference: United States Pharmacopeia. Yonkers, NY: Consumer Reports Books; 1998.

Footnotes