The SILS is a single item instrument for the identification of patients who need help with reading health related information. In this population, the SILS performs reasonably well. The S-TOFHLA takes up to seven minutes but the SILS is very brief and therefore practical for use during a routine clinical encounter.
Our finding of 17% prevalence of limited reading ability in an older population with chronic disease is lower than a recent pooled analyses of prevalence studies [22
] which reveal a weighted prevalence of low reading ability of 26% (95% confidence interval [CI] 22–29%) and of marginal reading ability of 20% (95% CI, 16%–23%). In the pooled analysis, level of education, ethnicity, and age were all associated with low reading ability. Our more educated and ethnically homogenous population may explain some of this difference.
Similar to Chew and colleagues'. [16
] single item questions, the SILS did not perform as well (sensitivity of 34%) for patients with marginal reading ability (S-TOFHLA scores 17–22). These false negative results may be because subjects may not recognize that they need help with reading, may be ashamed of a literacy problem. [23
], or may simply not understand the question.
The SILS had a larger area under the ROC curve for limited reading ability (the combination of impaired, inadequate or marginal reading ability) than any of the three questions proposed by Chew et al
] (c = 0.73 vs
. 0.68, 0.66, and 0.60). Although the area under the ROC curve is higher if we do not include those with marginal reading ability, we propose that this group of patients is also in need of additional assessment of their reading ability and potentially alternative methods of communication to optimize care.
Our sensitivity and specificity are similar to those reported by Bennett et al [15
] for the three item screening questions that they evaluated for use with adult caregivers of pediatric patients. These results add support to the feasibility of screening for reading difficulties in the clinical practice setting.
We chose the S-TOFHLA as the gold standard for this analysis because it is among the most widely used instruments for the assessment of health literacy. We would not expect, though, a perfect correlation between the two instruments. The SILS is measuring something distinct from reading ability, that is, the need for help with reading health-related materials. It is quite plausible, for example, that a person with adequate general literacy (and an adequate score on the S-TOFHLA), would routinely "need help" reading complex health information. If the intent is to determine who actually needs help reading health-related materials, the SILS is a more direct measure than the STOFHLA. More research is needed to understand the differences between populations identified by the SILS and the S-TOFHLA.
We envision the SILS being asked routinely at the time of patient registration or with the vital signs, as a potential first step to engage a patient in a dialogue about improving health related communication. Education and ethnicity have been reported to be significantly associated with health literacy [6
] and some may argue that these factors could be used to identify patients who are most in need of alternative communication strategies, rather than a new instrument. However, the SILS is a more direct assessment of a need and is simpler than an estimate based on demographic or cultural factors. Asking directly may also identify those with limited reading ability who already have a satisfactory compensatory strategy in place eliminating the need for further assessment.
This study has several limitations. The subjects were recipients of health care for diabetes in a single region of the United States, and may not be representative of patients from other areas. Most subjects had health insurance which reflects the fact that they were recruited from medical practices. A few subjects had the SILS read aloud to them while the majority responded to the SILS on paper, which may decrease the accuracy of the SILS in detecting limited reading ability. Future studies are needed to compare the performance of the SILS when read aloud versus administered on paper. Although our study sample is limited to a single region and is racially homogenous, all the subjects were outpatients with a chronic illness and should be representative of patients cared for in many community primary care settings in the U.S. We chose to use a cutoff of > 2 as in indicator of a positive SILS for this study, however in settings where the goal is to maximize sensitivity, using a threshold of > 1 should be strongly considered.