Spanish version of the Frontotemporal Dementia Knowledge Scale: adaptation and validation

ABSTRACT Background: Frontotemporal dementia (FTD) is a neurodegenerative disease and is one of the most common causes of dementia in people under 65. There is often a significant diagnostic delay, as FTD can be confused with other psychiatric conditions. A lack of knowledge regarding FTD by health professionals is one possible cause for this diagnostic confusion. Objectives: The aim of this study was to adapt and validate the Frontotemporal Dementia Knowledge Scale (FTDKS) in Spanish. Methods: A translation was done, following cross-cultural adaptation guidelines, which consisted of forward translation, blind back translation, and an analysis by a committee of experts. For the present study, 134 professionals from different health areas responded the Spanish version of the FTDKS. The statistical analysis was performed using R version 4.0.0 “Arbor day” and the Psych, sjPlot packages. Results: The Spanish version of the FTDKS had good reliability and internal consistency (Cronbach alpha 0.74.). The sample's mean score was 19.78 (range = 4-32, SD 6.3) out of a maximum of 36 points. Conclusions: The results obtained show that the Spanish version has good psychometric properties. The FTDKS is applicable in our environment and can be a useful tool to evaluate the knowledge of health professionals regarding frontotemporal dementia.


iNtrODUctiON
Frontotemporal dementia (FTD) is one of the most common causes of dementia in people under 65 years of age, and the third most prevalent cause of dementia altogether 1 .
Clinically, the FTD syndromes include the behavioral variant of FTD (bvFTD) and two language syndromes, the semantic (svPPA) and the nonfluent/agrammatic (nfvPPA) variants of primary progressive aphasia. Between these FTD syndromes, bvFTD is the most common clinical presentation. It is characterized by personality changes with behavioral disinhibition, apathy, loss of empathy, compulsive or ritualistic behavior, hyperorality, and dysexecutive symptoms 2 . In the language variants, the key component is progressive aphasia.
Unlike other dementias, such as Alzheimer's disease, FTD mainly affects behavior, language, or the motor system. Due to these characteristics, it is often misdiagnosed as a primary psychiatric illness 3 . Importantly, misdiagnosis has a negative impact on patients and their families who seek an answer to symptoms that continue to progress, compromising the patient' s personality, isolating them from social ties, undermining the family economy, and further disorienting the professionals who do not know how to deal with this disease. To support proper diagnosis, many workgroups have evaluated potential reasons for the diagnostic delay of FTD 4,5,6 . One study evaluated the mean duration from the onset of symptoms to the diagnosis of a neurodegenerative disorder in each of the FTD syndromes (3.7 years for bvFTD, 3.5 years for nfvPPA, and 1.4 for svPPA) 7 . The authors concluded the reasons behind this delay to be related to a misdiagnosis, with the symptoms of FTD being misattributed to a primary psychiatric disorder 3,4 .
Furthermore, we suspect that diagnosis errors could be even more important in Argentina and the surrounding region. For example, the estimated prevalence of FTD in the US for the population between 45 to 64 years is 15-22 per 100.000 8 . Based on these rates, Argentina (a country with approximately 10,040,258 inhabitants in that age range 9 ), should have a prevalence of 1,500 to 2,200 FTD cases. However, Argentina does not maintain an active countrywide registry of these cases, so no reliable epidemiological information regarding FTD exists. Fleni, situated in Buenos Aires, is one of the largest neurology tertiary referral centers in Argentina in which more than 1000 patients with dementia are evaluated annually and clinical care is integrated with extensive research programs. Despite this, Fleni has identified only 50 patients with FTD from its records from 2010 to the present day, likely representing an underestimation. In the literature, it is well recorded that the given prevalence varies from country to country and even in the same country from one study to another 7,8,10,11,12,13 . The main reason for this is that this disease is still missed and misdiagnosed and most numbers probably underestimate its true prevalence 4 . However, even if we ignore this fact and accept the estimated cases for this prevalence numbers, the recorded cases in Argentina seem to be below what we would estimate.
Based on these arguments and considering the prevalence and the frequent misdiagnosis, one possible explanation is that health professionals lack important knowledge regarding FTD and thus may fail to diagnose it in its early stages. Given this, it is essential to assess FTD knowledge among health professionals. To accomplish this, Wynn et al. developed the Frontotemporal Dementia Rating Scale (FTDKS). In this 18-item scale, the respondents answer objective questions about FTD using a 4-point Likert scale format (False, Probably False, Probably True, True), with an auxiliary "I don't know" option.
To understand the low frequency of FTD diagnosis in Argentina, our intention was to assess disease knowledge among health professionals. As a first step, we adapted the FTDKS scale into Spanish and report on its psychometric properties.

cross-cultural adaptation process
In order to initiate the adaptation to Spanish and validation of the FTDKS, we first asked for and obtained consent from the original author of the scale (Wynn et al.).
Following established guidelines 14 , adapting the FTDKS to Spanish involved four-steps: the forward translation, the blind back translation, a review by an expert committee, and administration to a validation sample.

Forward translation
The first stage in the adaptation process was translating the FTDKS into Spanish. A bilingual experimental psychologist from Argentina, familiar with both cultures, translated the survey into Spanish.

Blind back translation
A second independent translator, a clinician with the source language (English) as their mother tongue and who was blind to the original version, translated the scale back into English. This process revealed that the Spanish (translated) and English (original) versions reflected the same content.

Expert committee
A committee composed of a cognitive neurologist, neuropsychiatrist, neuropsychologist, and the two translators who performed the initial translation and backward translation assessed semantic, idiomatic, and conceptual equivalence of the Spanish FTDKS.

Final version
The final FTDKS Spanish version (Table 1), like the original version, consists of 18 items where respondents answer factual questions about FTD using a 4-point Likert-type scale format (False, Probably False, Probably True, True), with an auxiliary Don't Know option. Respondents receive 2 points for a correct True or False response, 1 point for a correct Probably True or Probably False response, and 0 points for an incorrect or Don't Know response.

Validation Sample
The final version of the Spanish FTDKS, along with a demographic questionnaire, was distributed in a Google Forms format among health professionals using snowball sampling techniques. The survey was distributed among colleagues using social networks and email, both directly and using professional groups from the leading Argentine societies of health professionals. In this way, 134 responses were obtained exclusively from health professionals (neurologists, psychiatrists, clinical psychologists, and neuropsychologists).
In addition to responses to the Spanish version of the FTDKS, demographic data was collected including: age, sex, education, professional discipline/specialty, years of experience, academical or research activities, health system where they work (public or private), practice settings, number of patients seen per month, self-reported knowledge of FTD (prior to answering the FTDKS), and clinical experience with dementia.
Results were analyzed to obtain a global Cronbach's α value. An isolated item analysis was performed to determine skewness, item difficulty, item discrimination, and global α if the item is deleted.
The item difficulty evaluates the proportion of respondents who answer an item correctly.
The item discrimination indicates how well an item discriminates respondents' knowledge. A high discrimination index indicates that the item works differently between respondents with higher and lower scores, suggesting that the item identifies respondents with more or less knowledge The statistical analysis was performed using R version 4.0.0 "Arbor day" and the Psych 15 , sjPlot 16 , and Table 2 packages 17 .

Sample characteristics
One hundred thirty-four health professionals completed the Spanish version of the FTDKS. There were no reported difficulties in understanding the instructions or in completion of the scale.
The sample characteristics are shown in Table 2. The mean age was 42.9 years (range = 25-77 years). Most of the professionals were highly educated and trained, with 80 (59.7%) having finished at least the residency and 82 (61.2%) having 8 or more years of clinical experience. The main area of work was with outpatients (n = 113), and most of the sample worked in the private sector (n = 77). Regarding experience, many of the professionals (n=66) saw more than 100 patients per month. Of the sample, the majority were neurologists (n=51), followed by psychiatrists (n=50) and clinical psychologists (n=15). From the total sample, 73 (54.5%) reported having academic or research-related activities. In terms of self-reported knowledge of FTD, the majority of professionals reported knowing "something" about the disease (n = 81), whereas a smaller percentage reported knowing "a lot" (n = 22) and only 1 respondent considered themselves an "expert" (n = 1).

Psychometric properties of the Spanish FtDKS
The mean score for the Spanish FTDKS was 19.78 (range = 4-32, SD 6.38). Table 1 shows the mean score per question for each item in the scale, the standard deviation (SD), the item difficulty, the item discrimination, and internal consistency (Cronbach α). The mean score per response ranged from 0.31 for statement 3 ("Among all people with dementia, 5-10% of them have frontotemporal dementia", False) to 1.66 for statement 1 ("Frontotemporal dementia is a type of Alzheimer disease", False). The internal consistency reliability (Cronbach α) for this sample was 0.74, 95% CI [0.67 ,0.8]), indicating acceptable reliability.