suggest that the Portuguese version of the Newest Vital Sign (NVS) should not be used to assess older adults in clinical practice because of a floor effect. We disagree. A floor effect is a problem when the performance on the test does not reflect the true performance in the domain being assessed.1 This is not the case here. We are not classifying older people incorrectly by using the NVS. Another study using a different health literacy instrument, one that asks people questions about their perceived difficulty performing health-related tasks, has also documented a very high proportion of limited health literacy in the older Portuguese population.
2In addition, it is also not the case that the educational level of the population used to validate the instrument was very different from that of the Portuguese population. The subgroup of 101 people from the general population in our study included 30.7% of participants with less than five years of schooling (the oldest of whom was 86 years old). This figure is close to schooling estimates from the Portuguese population near the time the study was conducted.3 Furthermore, when we compared this subgroup with the other more literate groups (physicians, health researchers, engineering researchers) we were not testing divergent validity (i.e. assessing whether constructs that are not supposed to be related are actually unrelated) but known-groups validity, which relies on administering the instrument to different groups that logically should have different levels of the construct to confirm whether the hypothesised difference was reflected in the scores of the groups. 4 We do agree with the authors in that the NVS should not be used as a proxy for poor health outcomes or poor medication self-management capacity. Concerning outcomes, the NVS can and has been used successfully to study the association between health literacy and health outcomes in studies that included older persons, but as a determinant and not as a proxy.5 Moreover, the study by Schillinger et al 6 cited by the authors to illustrate this point used the short version of the TOFHLA, 7 an instrument composed of two short cloze passages (an exercise where key words are deleted from a text and respondents are asked to fill in the blanks) and four very easy numeracy questions, which is quite unlike the NVS, as findings from studies using both the instruments can confirm. 8,9 Regarding self-management capacity, we also agree that it should not be used alone in samples with very low expected health literacy. If it is important to assess the numeracy component of health literacy (to assess skills related to timing, scheduling, and dosing of medications as well as numeric concepts needed to understand and act upon directions and recommendations, such as in the assessment of risk perception of an intervention) 10 in elderly samples, the NVS could be used in combination with another very brief instrument such as the Medical Term Recognition Test (METER), which has not displayed a floor effect.11 Nevertheless we argu...