Letter and category Fluency Test in Spanish-Speaking Children with Neurodevelopmental Disorders
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.310066
Source of Support: None, Conflict of Interest: None
Keywords: Executive function, language disorders, neuropsychological test, Speech Disorders
We have an individual and internalized knowledge of the vocabulary of language called lexicon. We can access it when we want to represent words of a specific action, object, or situation. This access to the object's name depends on the phonological skills and executive functions. There is a relationship between learning vocabulary and categorizing it in the lexicon because categorization requires the existence of mental representation of meaning, which is mapped to form lexical items.
The verbal fluency test can provide information about the storage capacity and the ability to retrieve information, and also evaluate the strategies used to search for words.
The verbal fluency test is a psychometric test, which is usually included in almost every neuropsychological assessment because it is sensitive to cognitive impairment from a variety of etiologies., It consists of two tasks: semantic category (or semantic fluency) and letter fluency (or phonological fluency). In the standard version of the test, in the first task, participants are given one minute to generate as many words as possible within a semantic category. For example, they are asked to say words from a given category that could be “food,” “animals,” “clothing” or “tools.” In the phonological fluency task, participants are asked to say as many as words as possible that start with a given letter. The sequence of letters usually used in an English version are “F”, “A”, and “S” (FAS). In children the number of letters or categories offered may be reduced to two. In Spanish-speaking countries, the use of the letters “P” and “M” have been proposed.
The widespread use of verbal fluency tests is probably due to the utility of the test for both executive control and verbal ability. Lexical access ability is the ability to retrieve the grammatical representations and sound forms of words from the mental lexicon. That is, those who have a larger vocabulary will produce more words than those with lower vocabulary. Children with dyslexia or with specific language impairment show a lower performance in these tests compared to typically developing children.
The validity of the fluency test as a tool to assess executive function is also well documented. Executive function is a set of functions that regulate thinking and behavior to achieve a goal. There is evidence in the literature about lower performance in both the verbal fluency tests by children with attention deficit hyperactive disorder (ADHD) and participants with frontal lobe lesions. For this reason, the administration of verbal fluency tests has been proposed for screening of cognitive deficiency in patients with impairment in executive functions such as Parkinson's, multiple sclerosis, or dementia.
Consistent with clinical observations, neuroimaging studies with healthy people have revealed the involvement of overlapping, but not the same, brain circuits during the two tasks. Semantic fluency was found to be associated with activation in ventral-anterior left inferior frontal gyrus; whereas phonological fluency was associated with the posterior-dorsally left frontal gyrus, as well as in presupplementary motor area and left caudate. In summary, both clinical and neuroimaging evidence suggest that verbal ability may be better reflected in the semantic than in the phonological fluency task, whereas executive ability may be more strongly reflected in the phonological fluency task.
Although extensive assessment of verbal ability and executive functions is important to obtain an accurate description of a patient's neuropsychological profile, such an evaluation is not always available in clinical practice. Therefore, the existence of a brief screening tool which is easy to administer and also detects verbal and executive deficits in patients would be of great value for clinicians working with them.
Despite the existence of some studies in pediatric performance on verbal fluency tasks, this test has not been as carefully studied as in adulthood. We did not find studies that analyzed the verbal fluency in relation to the neurodevelopmental disorders among Spanish-speaking children with letters P-M. For this reason, the objective of the present study was to analyze the performance of Spanish-speaking children in verbal fluency test comprising semantic and phonological tasks with letters P-M in order to know if it is possible to use this test to detect neurodevelopmental disorders in children.
We carried out a retrospective cross-sectional study to analyze the performance of Spanish-speaking children in the fluency test according to their intellectual level and their diagnosis. We included patients between 6 and 16 years old who had undergone a neuropsychological assessment with intellectual level and fluency verbal test between January and December of the 2016. Children with a known diagnosis of schizophrenia, autism spectrum disorder (ASD), bipolar disorder, Tourette syndrome, epilepsy, brain damage, or any other neurologic or genetic disorder were excluded. The patients who had diagnosis of attention deficit hyperactive disorder and had any comorbidity or were under any pharmacological treatment were also excluded.
The diagnoses of the selected patients were validated according to the Diagnostic and Statistical Manual of Mental Disorders IV (DSM IV). All the data were collected from the electronic medical s and neuropsychological assessments.
Patients underwent an extensive neuropsychological assessment, which included in all cases the Wechsler Intelligence Scale for Children version IV (WISC IV) and neuropsychological battery NEPSY II (Development Neuropsychological Assessment, II Edition, Spanish version) (subtest Verbal Fluency with phonological and semantic task). Phonological Fluency test consisted two one-minute trials in which patients were asked to say as much words as possible beginning with letters “M” and “P”. In the semantic fluency task, the participants were given one minute to list animals and then another minute to list foods and drinks. All the assessments were administered under similar conditions by neuropsychologists.
Cognitive ability was assessed using Wechsler Intelligence Scale for Children version IV (WISC IV) to obtain an estimate full-scale IQ (FSIQ) (using all required subtest). We used the standard score with a median of 100 and a standard deviation of 15 for the analysis. In the analysis of the subtest of the Nepsy II fluency verbal test, we used scale scores which have a median of 10 and a standard deviation of 3. Continuous variables were expressed as mean or median according to their distribution. Categorical variables were expressed in absolute numbers or proportions. The comparisons among diagnostic categories were carried out with Kruskal–Wallis for continuous variables and with Chi square test for categorical variables. For the purpose of the analysis, the population was divided according to their FSIQ in two groups. Children with IQ <80 were classified in the group called low intellectual performance (LIP).
The relationship between phonological fluency task (PF) and semantic fluency task (SF) with the intelligence quotient (IQ) was analyzed using Chi square test, considering PF and SF as dichotomous variables using scale score of 7 as cutoff value. To analyze the association between low intellectual performance and fluency, we used a logistic regression model adjusted by sex and age. Statistical significance was considered at P < 0.05.
The research was conducted according to the principles of the Helsinki Declaration and in compliance to all mandatory laboratory health and safety procedures.
We included 164 patients with a mean age of 10.45 years (SD ± 2.46). There were 113 males (68.90%). The mean scalar scale in the semantic fluency test (SF) was 7.56 and that of the phonological verbal fluency test was 5.64. The full-scale intelligence quotient (FSIQ) mean was 79.36 (SD ± 15.71).
[Table 1] describes the characteristics of the patients according to the diagnostic category such as low intellectual performance (LIP), dyslexia, and attention deficit disorder. There were no differences with relation to age and sex among the three groups. Patients with LIP showed lower phonological fluency than patients with ADHD. As for semantic fluidity, we observed differences between patients with LIP and Dyslexia and also between LIP and ADHD.
Considering the diagnoses, the population was distributed as follows: 55 (33.54%) patients showed LIP, 19 (11.59%) patients had a diagnosis of dyslexia and 90 (54.88%) patients had an ADHD. [Table 2] shows the proportion of patients with low performance in phonological fluency and semantics fluency tasks according to diagnosis.
Upon logistic regression analyses, we observed that the probability of having LIP when somebody had had a scale score lower than 7 in the PF task was 9.6 times greater (OR = 9.66, P < 0.001; IC 95% = 3.26–28.63). On the other hand, we observed that the probability of having LIP when somebody had had a scale score lower than 7 in the SF task was 16.7 times greater (OR = 16.76, P < 0.001; IC 95% = 7.42–37.84). The effect was unchanged after adjusting for sex and age [Table 3].
The verbal fluency test is a psychometric tool for neuropsychological assessment, because it has the ability to detect dysfunction in executive functions and verbal skills. The performance will be affected differently because the SF is usually affected by verbal skills whereas the PF by the executive functions. These findings are independent of ethnic, sex, or cultural aspects.
The difference in the performance in PF and SF may suggest that there could be a different retrieval mechanisms employed in each task. For example, the retrieval of a word (e.g., tomato) will activate semantically associated words (e.g., egg, meat); so that SF task resembles everyday production and participants can exploit existing links between related concepts to retrieved response. By contrast, the links between words beginning with the same letter may be less accessible so that participants must suppress the activation of semantically or associatively related words and require novel search strategies to carry out the PF task. In addition, the PF task may engage cognitive skills like executive function whose deficits can be explained by fluid intelligence.
There are studies that have documented poor PF performance by patients with language and reading disorders who were given the test with the letters “F”, “A”, and “S”. In accordance, in our study, using the letters “P” and “M”, 73% of the patients with dyslexia failed in PF whereas only 18% failed in SF. Therefore, we could assume that in patients with dyslexia, the results obtained by using the Spanish version of the fluency verbal test, with the letters “P” and “M”, are similar to those found with the letters “F”, “A”, and “S”.
On the other hand, a lower performance by ADHD patients had been reported in PF task with the letters “F”, “A”, and “S”. Those results were not associated with sex, age, and educational level. In agreement with the literature, we found that in our population, 52% of the ADHD patients failed in the PF task. Based on these findings, we could also infer that the results obtained using the Spanish version of the PF test in patients with ADHD, using the letters “P” and “M”, are similar to those found with the letters “F” and “S”.
Finally, the present study demonstrates that there is a direct relationship between FSIQ and the performance in the verbal fluency test in our population, because those patients who obtained a PF score less than 7 were nine times more likely to have a LIP and those who obtained a low performance in the SF task were nearly sixteen times more likely to have an LIP than those who achieved a typical performance on those test.
The present study has some limitations that should be taken into account in future researchs. This study population consisted participants who had undergone neuropsychological assessments and referred to the Child Neurology Department. Therefore, the results could be different to those in a typically developing population.
Nevertheless, and beyond these limitations, we believe that our results have an important clinical implication because we did not find studies that analyzed verbal fluency with relation to neurodevelopmental disorders with letters P-M among Spanish-speaking children. Since the access and the necessary time for an extensive neuropsychological assessment are not always available, we observed that verbal fluency testing with letters P-M could be a brief and effective neuropsychological tool in detecting neurodevelopmental disorders among Spanish-speaking children, especially deficit in executive functions, verbal abilities, and LIP.
Although no single test can replace the value of a complete neuropsychological assessment, our study reveals that the verbal fluency test with letters P-M could be used as a brief, reliable, and easily tool to identify neurodevelopmental disorder among Spanish-speaking children. Those patients with poor performance in this test should perform a complete neuropsychological assessment in order to confirm the diagnosis.
Ethics of experimentation
The authors state that the research was conducted according to the principles of the Helsinki Declaration and in compliance with all the mandatory laboratory health and safety procedures.
Financial support and sponsorship
This work was supported by the authors
Conflicts of interest
There are no conflicts of interest.
[Table 1], [Table 2], [Table 3]