A Chinese version of the Language Screening Test (CLAST) for early-stage stroke patients
A Chinese version of the Language Screening Test (CLAST) for early-stage stroke patients
Hongyan Yang 0 1 2
Shenghua Tian 0 2
Constance Flamand-Roze 0 2
Ling Gao 0 1 2
Wei Zhang 0 2
Yan Li 0 2
Jiajia Wang 0 2
Zhou Sun 0 1 2
Ying Su 0 1 2
Libin Zhao 0 2
Zhihou Liang 0 1 2
0 Current address: Department of Neurology, Longhua Branch of Shenzhen People's Hospital , ShenZhen, Guangdong , China
1 Department of Neurology, Union Hospital, Tongji Medical College, Huazhong Science & Technology University , Wuhan, Hubei , China , 2 Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong Science & Technology University , Wuhan, Hubei , China , 3 Department of Neurology, Centre Hospitalier du Sud Francilien, Corbeil-Essonne, France, 4 Department of Neurology, First Affiliated Hospital of Shanxi Medical University , Taiyuan, Shanxi , China , 5 Department of Neurology, Luoyang Central hospital affiliated to Zhengzhou University , Luoyang, Henan , China , 6 Department of Neurology, Binzhou people's hospital , Binzhou, Shandong , China , 7 Department of Anesthesia, Maternal & Child Health Hospital of Bao'an District , Shenzhen, Guangdong , China
2 Editor: Jong-Ling Fuh, Taipei Veterans General Hospital , TAIWAN
There is a severe lack of aphasia screening tools for bedside use in Chinese. A number of aphasia assessment tools have recently been developed abroad, but some of these scales were not suitable for patients with acute stroke. The Language Screening Test (which includes two parallel versions [a/b]) in French has been proven to be an effective and time-saving aphasia screening scale for early-stage stroke patients. Therefore, we worked out a Chinese version of the LAST taking into consideration Chinese language and culture. Two preliminary parallel versions (a/b) were tested on 154 patients with stroke at acute phase and 107 patients with stroke at non-acute phase, with the Western Aphasia Battery serving as a gold standard. The equivalence between the two parallel versions and the reliability/validity of each version were assessed. The median time to complete one preliminary Chinese version (each had some item redundancy) was 98 seconds. Two final parallel versions were established after adjustment/elimination of the redundant items and were found to be equivalent (intra-class correlation coefficient: 0.991). Internal consistency is(Cronbach α for each version [a/b] was 0.956 and 0.965, respectively) good. Internal validity was fine: (a) no floor or ceiling effect/item redundancy; (b) construct validity revealed a 1-dimension structure, just like the French version. The higher educated subjects scored higher than their lower educated counterparts (p<0.01). The external validity: at the optimum cut-off point where the score of version a/b <14 in higher educated group(<13 in lower): the specificity of each version was 0.878/0.902(1/1 in lower) and sensitivity was 0.972/0.944(0.944/0.944 in lower). Inter-rater equivalence (intra-
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
Funding: The author(s) received no specific
funding for this.
Competing interests: The authors have declared
that no competing interests exist.
class correlation coefficient) was 1. The Chinese version of the Language Screening Test was
proved to be an efficient and time-saving bedside aphasia screening tool for stroke patients at
acute phase and can be used by an average medical physician.
Aphasia represents one of the most common consequence of stroke[
], and affects about
onethird of acute-phase stroke patients. It lowers quality of life, affects social interaction, and even
]. Godecke et al demonstrated that a very early aphasia therapy for mild to
severe aphasia of post-stroke patients proved to be significantly effective over short and medium
term at follow-up (six months), and that the timing and intensity of aphasia therapy post-stroke
were significantly associated with the recovery of communication ability[3±5]. Most
well-established scales for aphasia diagnosis, such as the Western Aphasia Battery (WAB) and the Boston
Diagnostic Aphasia Evaluation (BDAE), are too long to complete, especially during the acute
phase of stroke, and must be administered by speech and language therapists[6±8]. A number
of aphasia assessment tools for bedside use have recently been developed[9±17], but such scales
remain unavailable in China. Moreover, some of the aforementioned scales have some
limitations in terms of administration, such as requiring stimulus cards to be readily available[
Application of some tests is limited by the presence of visual field deficits, visual neglect or
inattention, illiteracy, deafness.[
]; Some tests have no norms against which to interpret scores
],and some scales only address particular expressive language skills such as semantic
verbal fluency [
]; Moreover, some test have been proved to be insensitive [
The Language Screening Test (LAST) in French generated by Constance Flamand-Roze,
which was designed for aphasia screening in emergency setting, avoids the aforementioned
shortcomings and has been proved to be suitable for routine bedside evaluation of patients
with acute stroke in clinical practice[
]. The released German version of the LAST has also
been proved to be reliable and valid[
]. Therefore, LAST may has good language flexibility or
compatibility and can be easily tailored into a different language version by making some slight
modifications according to a certain linguistic and cultural context. Thus, we generated a
Chinese version of the LAST (CLAST) by taking into account Chinese language and culture, and
tested the CLAST in post-stroke patients from several areas geographically located in Henan,
Shandong, Shanxi, and Hubei provinces, with an attempt to develop an efficient and
time-saving bedside aphasia screening tool for Chinese-speaking patients suffering from acute-phase
The study was approved by the Clinical Trial Ethics Committee of Huazhong University of
Science and Technology, Wuhan, China. (Approval NO. S102). Verbal informed consent was
obtained from all recruited subjects or their legally acceptable representatives prior to the
Development of the CLAST (Key elements of study design)
Features of the LAST. To avoid retest bias of the LAST, two parallel versions were
constructed. Each item on the two scales was different (apart from the automatic speech item) but
strictly matched. Each version of the LAST consisted of 5 subtests and a total of 15 items. One
(1) point was awarded for correct answers given within 5 s, otherwise the score was zero (0).
The maximum score was 15, covering two sub-scores, namely, an expression index (including
naming, repetition, and automatic speech; the "maximum " score was 8) and a receptive index
(including picture recognition and verbal instructions; the "maximum" score was 7). The
subitems are detailed under the following subheading.
Modifications of sub-items(similarities and differences between LAST and initial
CLAST). To help us achieve better accuracy in the scale adaptation, the French authors of
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LAST gave us a great many help, including translation and back-translation and cross-cultural
adaptation of the items. By referring to the design principles of the LAST[
], and considering
the difference in everyday familiarity (subjective verbal frequency) between Chinese and
], we made some slight modifications as follows. The different versions CLAST
are provided in Appendices(S1±S3 Files).
Our CLAST also consists of five subtests, but some modifications were made: (1) in naming
of five black-and-white drawings, considering the cultural difference between Chinese and
French, ªdinner knifeº in LAST-b was replaced by ªchopsticksº with nearby verbal frequency
in CLAST-b; (2) in oral repetition, to keep the same number of syllables with LAST, some
small adjustments, such as reducing function words, were made according to syntactic rules of
Chinese. As a result, we came up with one word with 4 syllables and one sentence with 11
syllables with semantically consistent with LAST; (3) in automatic speech, i.e. counting from 1 to
10; sentences were left semantically unchanged in LAST. (4) in picture recognition, complex
items replacements were made given that distractors were more complicated in Chinese, the
replaced items are detailed in the next paragraph; (5) in execution of three verbal commands
(simple, semicomplex,complex), sentences were also left semantically unchanged in LAST.
Details of picture-recognition: in LAST, four orally presented target words were depicted
within a set of eight pictures, with the four distractor pictures being either visually, semantically,
phonologically or visually related to one of the target words, complex item replcements were
made considering that distractors are more complicated in Chinese. In the CLAST, the semantic
and visual pairs of distractors in the LAST were adopted and were left semantically unchanged.
Nonetheless, the distractors are more complicated in the CLAST than in the LAST since in
Chinese language phonological and semantic distractions are interwoven and/or concomitant. The
replacements were selected from common objects based on frequencies of Chinese words and
]. For example, in the LAST-a ªlapinº (rabbit) and it's phonological distractors
ªpinº (pine) were replaced by ªSongshuÏº (squirrel) and it's interwoven phonological and
semantic distractors ªSongshuÁº (pine); Similar, ªcuillèreº (spoon) and ªlait cailleÂº (cheese) were
replaced by ªYiguÁõº (wardrobe) and ªYijiàº (hanger), in the LAST-b, ªchapeauº (cap) and
ªgateauº (cake) were replaced by ªbàozhiº (newspapers) and ªbāoziº (steamed stuffed bun); and
ªmainº (hand) and ªpainº (bread) were replaced by ªshuÅõtoÏngº (bucket) and ªshuÅõhuÂº (kettle).
To avoid possible failure, we prepared a backup pair of semantic distractors to the ªPicture
recognitionº subtest of each version, but it was end up by discarding the reserves for item redundancy.
As a result, the ªPicture recognitionº subtest of our initial CLAST contained five items (with five
corresponding distractors). The replaced pictures in the CLAST were drawn by the same artist of
LAST to ensure the consistency of the style. The comparsion of distractors between LAST and
CLAST are included as Appendices(S6 File).
Patients and instruments
To verify the reliability and validity of CLAST, we enrolled stroke patients at ªacute-phaseº and
ªnon-acute phaseº. The consecutive ªacute-phaseº patients included were from the departments
of neurology of four general hospitals: Union Hospital of Tongji Medical College, Huazhong
Science & Technology University; the First Hospital of Shanxi Medical University; Luoyang
Central Hospital Affiliated with Zhengzhou University; and Binzhou People's Hospital with
time frame lasting from August to October in 2014.
Patients at ªnon-acute phaseº were divided to an aphasic group and a non-aphasic group
with the WAB serving as a gold standard[
]. Considering the short hospitalization time and
the feasibility to complete the test of the WAB of the stroke patients, patients who were 10 days
after stroke onset was defined as the patients at ªNon-acuteº phase in our test. Non-aphasia
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patients were enrolled from August to October, and their aphasia counterparts were from
August to December in 2014.
The demographic information of the participants, including educational background,
together with clinical diagnosis, including imaging findings, was collected.
Inclusion criteria. Patients with Mandarin as their native language and satisfied the
following criteria were included:(1) within 3 days after stroke onset (acute-phase patients) and (2)
had stroke attacks 10 days' later(including those who had stroke episodes a few years ago) and
was able to complete the WAB (patients with stroke at non-acute phase). Stroke was confirmed
by brain radiological imaging(Computed Tomography or Magnetic Resonance Imaging).
Exclusion criteria. Patients were excluded from study if they met any of the following: (1)
being mentally retarded or demented premorbidly at the time of study or before this stroke
episode; or having (2)psychiatric disorders;(3)visual problems;(4)auditory
problems;(5)consciousness disorders(score of Glasgow Coma Scale (GCS) <15);(6)native language was not
We tested the CLAST in post-stroke patients from several areas geographically located in
Henan, Shandong, Shanxi, and Hubei provinces. Both the CLAST-a and CLAST-b were used
in all patients. Nine examiners were involved in our test: three examiners worked forUnion
Hospital of Tongji Medical College, Huazhong Science & Technology University; the other six
were from the First Hospital of Shanxi Medical University, Luoyang Central Hospital, and
Binzhou People's Hospital, with two coming from each hospital.
Test procedure in the acute-phase patients. CLAST-a and CLAST-b was administered
alternately as the first test for the consecutive patients. During the interval between the two
tests, the subjects were evaluated with the National Institutes of Health Stroke Scale (NIHSS).
To assess inter-rater reliability, during the the first test(by CLAST-a or CLAST-b), two
examiners rated the patients at bedside(a doctor who had received professional training in
conducting a number of aphasia scales such as WAB, BDAE,CLAST, etc; and a resident who was
randomly selected from students on a standardized training program, given a 5-minute
training session for the test). One of the examiners asked the patient questions according to the first
test(by CLAST-a or CLAST-b, namely, version-a or version-b of CLAST), meanwhile, the two
examiners made their judgment independently, and the amount of time taken to finish the test
was recorded. Following an interval specified by NIHSS, the other version-b/a of CLAST was
administered by the examiner who hadn't questioned the patients in the first round.
Test procedure in the non-acute stroke patients. Participants were first given the WAB
to determine if they had aphasia by one examiner, who was blinded to the site of stroke lesion
]. Afterwards, the CLAST-a and CLAST-b and NIHSS were administered in the same way
they were given to the acute-phase patients(only one examiner accomplished that procedure).
To reduce potential bias of assessment, the rating of the WAB was undertaken by one
examiner who had received professional training in conducting a number of aphasia scales such as
WAB, BDAE, CLAST, etc. The WAB and CLAST were administered by two different
examiners who were blind to the results of the other examiner, and all the examiners were blind to the
sites of stroke lesion.
The flow-chart of the above-mentioned tests in all patients is given in Fig 1 below.
Validation of the CLAST
The CLAST was validated in terms of the following aspects: the equivalence between the two
versions, the internal validity of the two versions (including item redundancy, ceiling and
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Fig 1. The flow chart to administer aphasia scales in acute and non-acute stroke patients.
floor effect, construct validity, and discrimination validity). External validity against the WAB
and reliability (including internal consistency and inter-rater reliability), the relation between
CLAST scores and educational background. A schematic representation of the study design is
shown in Fig 2.
The equivalence between the two versions of the CLAST was assessed by calculating the
intraclass correlation coefficient (ICC) from the two total scores and parallel items[
validity was assessed in terms of four aspects. First, the Spearman correlation matrix was used to
detect item redundancy[
]. Second, the ceiling or floor effect was detected. The floor and ceiling
effects, the percentages of the sample scoring the minimum and maximum possible scores,
respectively, reflect the extent that scores cluster at the bottom and top of the scale range. Floor
and ceiling effects <20% were considered to be significant. Third, construct validity was
determined by utilizing exploratory factor analysis[
]. Factor analysis was carried out as follows.
General Least Squares were used to extract factors. Oblique rotations were adopted in order to
detect the correlations between the extracted factors. We protocol to use the scree test to
determining the most appropriate number of factors to retain. Then, the Mann-Whitney U test was
employed to compare the score of aphasia patients with their non-aphasia counterparts to verify
discrimination validity(It was assumed that non-aphasia patients would have higher scores than
aphasia patients, p<0.01). We computed Cronbach α to obtain the internal consistency. The
ICC was used to represent inter-rater reliability. The external validity was obtained by plotting
the receiver operating characteristic (ROC) curve, and the area under the ROC curve was used to
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Fig 2. Schematic representation of validation process of Chinese version of the Language Screening Test (CLAST).
Please note that the floor and ceiling effects were assessed in aphasia group, and discrimination validity was assessed in
the non-acute group.
indicate the diagnostic accuracy of the CLAST. The closer the ROC curve to the upper left-hand
corner, the higher the overall accuracy of the test[
]. The Mann-Whitney U test was utilized to
compare the performance of the two groups of different education levels (higher-educated
patients who received junior middle school education and above vs. lower-educated patients who
received elementary education and below) to understand the relationship between CLAST scores
and educational background.
SPSS19.0 software package was used for all the statistical analyses.
Acute-phase patients: One hundred sixty seven consecutive patients were admitted to the
neurology departments for suspected acute stroke during a 5-month period. Thirteen patients
were excluded (severe consciousness impairment [n = 5], blindness [n = 3], history of
dementia [n = 2], deafness [n = 1], psychiatric disorders [n = 1], refusal to participate [n = 1]). The
remaining 154 acute patients were included. Their post-stroke time range from 1 to 3 day(s),
the average and median time being 1.95 and 2 days respectively. Their mean age was 60.21
years (range: 24 to 88 years). Of them, 112 were males. Most of the patients (90.3%) had
cerebral infarction. Their median NIHSS score was 3.00 (interquartile range: 4.25). The
distribution of their educational levels is shown in Table 1.
Non-acute phase patients: This group consisted of 107 patients hospitalized at Wuhan Union
Hospital of Tongji Medical College, Huazhong Science & Technology University, including 53
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aphasia patients and 54 non-aphasia patients, diagnosed against the Western Aphasia Battery.
Their mean age was 56.03 years, ranging from 24 to 79. Most patients (88.8%) had cerebral
infarction. The aphasia group had 40 males and 13 females (mean age: 57.72 years and range: 25
to 76), while the non-aphasia group included 43 males and 11 females (mean age: 54.37 years,
and range: 24 to 79). In the non-acute group, the 107 patients were recruited, with their
poststroke time ranging from 10 to 1147 days after the stroke onset, and the average and median
durations being respectively 65.6 and 14 days. The baseline data of the acute phase and
nonacute phase patients with stroke are presented in Table 1.
When we detected the item redundancy of initial CLAST by using Spearman's correlation
matrix, we found some item redundancies both in CLAST-a and CLAST-b(details are given
insupplementary data,S4 File- The item redundancies in initial CLAST). Then these redundant
items were removed and swapped to give a 14 item version of the CLAST (Final CLAST),
details are listed in supplementary data S5 File -The adjustment of items in initial CLAST to
overcome item redundancy. The data of the final CLAST could be obtained by ªexchangingº
scores of the paralleled items and ªdeletingº the scores of removed items from the data of
initial CLAST, So the data of initial and final CLAST were both obtained from the original 261
patients, and no reassessment was conductedon the final CLAST. The final CLAST was then
re-validated in the original subjects as follows (the Chinese and English version of the final
CLAST are appended in the supporting information, S1±S3 Files).
Time taken to complete the initial CLAST. All participants underwent the initial 16 item
version of the CLAST, which took 98 seconds(median time) to administer. The time taken to
complete 16 items lasted from 45 to 196 seconds and the interquartile range was 55 seconds.
Internal validity of the final CLAST. Spearman coefficients ranged from 0.3 to 0.9,
suggesting that there was no item redundancy in the final CLAST. In terms of the floor and ceiling
effects, in the 53 patients with aphasia enrolled, the percentages of the sample scoring the
maximum were respectively 0% and 1.9% in CLAST-a and CLAST-b, and the percentages of the
sample scoring the minimum were 7.5% and 5.7%, demonstrating that there was neither a floor
nor a ceiling effect with both versions. Factor analysis (by General Least Squares, Oblique
rotations and the scree test as aforementioned) revealed a two-factor solution, the two factors, with
both eigenvalues above 1.0, explained variance of 70.860% in CLAST-a(74.261% in CLAST-b),
We only recorded the lesion sites of the non-acute patients, exclusive of the patients in the acute phase. a: Tertiary degrees or above; b: High school or technical
secondary school; c: Junior middle school; d: Elementary school; e: Illiterate. A: Left hemisphere; B: Right hemisphere; C: Cerebellum/brainstem; D: Bilateral
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but the two factors were highly correlated with a correlation coefficient of 0.624 in CLAST-a
(0.762 in CLAST-b). Hence, we tried to merge the two related factors, namely, we limited the
number of extracted factor to 1 with each version. Then, the sole factor accounted for 63.564%
of the explained variance in CLAST-a (67.532% in CLAST-b),the factor loading of the 14 items
of CLAST-a ranged from 0.488 to 0.930(and from 0.678 to 0.964 in CLAST-b), just as the
acknowledged view: with high(0.80 and above) and mid-range factor loadings (0.40±0.60)[
Table 2 shows the loading of each item on the factor of each CLAST version. So, the CLAST,
similar to the French LAST, can be said to reveal 1-dimensional structure. The Mann-Whitney
U test showed that non-aphasia patients outperformed their aphasia counterparts with both
versions (The sum of ranks in the non-aphasia group were 4310/4300 in CLAST-a/b against 1468/
1478 in the aphasia group, p = 0.000<0.01 with both CLAST-a and CLAST-b), and
discrimination validity was good.
Reliability of the CLAST. The internal consistency of the 14 items was good, with a
Cronbach α of 0.956 with the CLAST-a and 0.965 with the CLAST-b. The Cronbach α of each
subtest in the CLAST-a and CLAST-b ranged from 0.701 to 1.
Inter-rater reliability. The ICC among different raters was 1.
Equivalence between the CLAST-a and CLAST-b. The mean total score on the CLAST-a
was 10.43 (10.60 on the CLAST-b) and the ICC between the two versions was 0.991. When the
automatic speech item, which was identical in both versions, was removed, the ICC (0.989)
did not change significantly. The ICC between parallel items in the two versions ranged from
0.786 to 0.983.
The items in CLAST were presented as the above short form, their original form were detailed as follows. Variables in
CLAST-a: Telep-Telepho ne; Pen-Pen; Pine-Pineapple; Croc-Crocodile; Chop-Chopsticks; Math-Mathematics; The-The
post man brings a letter to my neighbor; Auto-Automatic speech; Squi-Squirrel; Armo-Armoire; Ciga-Cigarette; Eye-Eye;
Don't d-Don't take the drinking-class but the pen; Put-Put a hand on your head, then a finger on your nose. Variables in
CLAST-b: Penc-Pencil; Telev-Tele vision;Fork-Fork; Gira-Giraffe; Butt-Butterfly; Lite-Literatu re; Vaca-Vaca tioners
would like strawberry ce-cream;Auto-Automatic speech; News-Newspaper; Pail-Pail; Car-Car; Toma-Tom ato; Don't
bDon't take the book but the keys; Touc-Touc h one of yours ears with one finger, then your foerhead with two fingers.
The relationship between educational levels and CLAST scores. The Mann-Whitney U
test showed that the 163 subjects in the higher educational level group earned higher scores
than the 88 ones in the lower-level education group. The difference was statistically significant
(pCLAST-a = 0.000<0.01, pCLAST-b = 0.003<0.01).
Fig 3 shows the box plot representing the distribution of the total scores of CLAST-a and
CLAST-b with regard to different educational levels(n = 261).
External validity. The diagnosis of aphasia can be establishedwhen the Aphasia Quotient
(AQ) of WAB is <93.8 out of 100 [
]. The optimal cut-off point (score) of the CLAST varied
with different educational levels (Fig 4A and 4B represents the patients with higher and lower
educational levels, respectively).
Fig 5 shows the correlations between the total score of the CLAST and WAB on a scatter
diagram (Spearman coefficient between the CLAST and WAB was 0.920 (rhoCLAST-a) or 0.921
Fig 6 shows the correlation between the subtests of the CLAST-a and CLAST-b (with rho
ranging from 0.68 to 0.885) on a histogram (rho was greater than 0.7 for all, except that
correlation between ªPicture recognitionº of the CLAST-b and "Auditory comprehension" of the
WAB was 0.68).
Our study showed that the final CLAST designed for screening aphasia in acute stroke patients
was convenient and effective. The equivalence between the two versions of the CLAST was
good. Both versions also had good inter-rater reliability, internal consistency, and validity. The
external validity against the WAB was also good (the area under the ROC was 0.969 and the
parallel items between the CLAST and WAB were well correlated). The median time to
complete one initial version of CLAST was 98 seconds. The test could be carried out by an average
medical physician. This CLAST is the first Chinese version of the LAST for quick screening of
aphasia in acute stroke patients.
Fig 3. Box plot representing the total scores of the Chinese version of the Language Screening Test (CLAST-a/
CLAST-b) in terms of educational levels. The maximum and the lower quartile of CLAST score were found to be
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Fig 4. Receiver operating characteristic (ROC) curve of the Chinese version of the Language Screening Test
(CLAST) in comparison with the Western Aphasia Battery (WAB) used for external validation. The blue, green,
and red curves respectively represent CLAST-a, CLAST-b, add CLAST-a and CLAST-b combined. (A) In higher-level
education group, at the point where CLAST-a score or CLAST-b score <14, specificity was 0.878 or 0.902 and sensitivity
was 0.972 or 0.944. At the point where the combined score of CLAST-a and CLAST-b <27, the specificity was 0.902 and
sensitivity was 0.944. (B) In lower-level education group, at the point where CLAST-a score or CLAST-b score <13,
specificity of both (CLAST-a and CLAST-b) was 1 and sensitivity of both was 0.944. At the point where the combined
score of CLAST-a and CLAST-b <26, both specificity and sensitivity were 1.
The CLAST has several advantages which are similar with LAST: it's simple and easy to
administer by any physician and avoids the impact of pre-existing illiteracy and hand paresis.
Furthermore, the availability of two equivalent parallel versions minimizes possible retest effects.
The CLAST versus LAST: In the LAST study, either the LAST-a or LAST-b was used on a
random basis and the data were pooled for analysis after the equivalence verification [
Fig 5. Scatter diagram between Aphasia quotient (AQ) of the Western Aphasia Battery (WAB) and total scores of
the Chinese version of the Language Screening Test (CLAST-a/CLAST-b). The correlation between AQ of WAB
and total score of CLAST-a/CLAST-b is represented by blue circles and green circles, respectively.
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Fig 6. Histographic representation of the correlation between the Chinese version of the (CLAST) subtests and
corresponding Western Aphasia Battery (WAB) items. The CLAST-a and CLAST-b are indicated by white and
black bars, respectively. The coefficient of correlation between the CLAST and WAB ranged from 0.68 to 0.885
this study, we tested the reliability and validity of each version separately (i.e., testing both
versions of the CLAST in each single subject enrolled). When the two Chinese versions combined
with each other, sensitivity and/or specificity may be further improved in clinical practice.
Compared with the LAST, the CLAST is different in a number of respects: (1) Patients with
a higher-level education (junior middle school education and above) outdid their counterparts
receiving lower-level education (only elementary school education and below) on the CLAST,
suggesting that patients' performance on the CLAST might be influenced by their educational
background. Perhaps the items of CLAST we selected influence outcome, or the national
cultural of China lead to language hierarchy in different educational background. (2) The ROC
curve demonstrated that the external validity of the CLAST-a and CLAST-b was not as good as
that of the LAST, and the optimal cut-off scores varied with different educational levels. In
patients with lower educational levels, both sensitivity and specificity were 1 when the CLAST-a
and CLAST-b were used in combination at the point of at which the total scores of CLAST-a
and CLAST-b<26. Therefore, we suggest that to improve the screening accuracy in patients
with lower educational levels, both versions of the CLAST should be used if conditions permit.
The present study had some limitations: Firstly, in our non-acute phase sample, patients were
not included consecutively, and it was likely that the full spectrum of aphasia severity was not
represented in the study cohort, which might increase the possibility of selection bias.
Furthermore, the external validity was verified only in the stroke patients at non-acute phase because no
generally-accepted diagnostic criteria for emergent aphasia were available. Finally, only the
initial CLAST which had same item redundancy was administered in our enrolled patients, the
final CLAST scores were obtained merely by ªexchangingº and ªdeletingº scores from the initial
CLAST in the enrolled patients, and the time to administer final CALST were beyond
computation in our test. It might be better to re-validate the final CLAST in new groups.
The final CLAST detected a language deficit (when the CLAST-a and CLAST-b was <26
for patients with lower educational levels and the CLAST-a or CLAST-b was <14 for patients
with higher educational levels) in 42.9% of the 154 patients admitted to our research centers,
whereas aphasia was reported in only 17% to 38% of patients in other acute stroke series. The
possible reasons might be: (1) the CLAST might have a higher sensitivity for aphasia; (2) early
testing of the acute phase patients (within 72 hours after stroke onset), thus identifying patients
who would go on to recover rapidly; (3) the acute patients had lower educational level on
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average and thus possibly higher yield rate. Identification of false-positive (nonaphasic)
patients such as (a) patients with dysarthria; and (b) patients with initiative/executive
dysfunctions (for example, the maximal response time of 5 seconds could penalize patients with
initiative disorders); (c) in picture recognition subitems, the use of homophones with interwoven
semantic relatedness as distractors might well increase the difficulty and then increase the
false-positive rate, which might be more evident in patients with inadequate attention, and
when the test was administered in patients who spoke dialectic versions of Mandarin.
In terms of educational levels, the maximum and the lower quartile of CLAST score were
found to be identical.The possible reasons might be: (1)The number of non-aphasia patients
(142 patients in total, composed by 54 patients referring by the WAB from the non-acute
phase; and 88 patients, 57.1% from the 154 acute phase patients) out-numbered the aphasia
ones (119 patients intotal, composed by 53 patients referring by the WAB from the non-acute
phase; and 66 patients, 42.9% from the 154 acute phase patients); (2)Our research centers are
general wards, and more patients with relatively minor to moderate stroke were enrolled (The
median of NIHSS score was 3/5 in the acute/non-acute phase); (3) The sample size in terms of
different educational levels might not be big enough, and the abnormal distribution of CLAST
score might result;(4) CLAST may be deficient in discerning the aphasia severity.
To summarize, our study showed that the CLAST can be used at bedside and was proved to
be a rapid and efficient tool for screening aphasia in patients with acute-phase stroke. Whether
the CLAST has the potential for estimating the severity, evaluating outcome, or forecasting
prognosis of aphasia in early post-stroke patients warrants further studies.
S1 File. Chinese version of the final CLAST and instructions of the final CLAST.
S2 File. English version of CLAST-a.
S3 File. English version of CLAST-b.
S4 File. The item redundancy details in initial CLAST.
S5 File. The adjustment of redundant items in initial CLAST.
S6 File. The comparsion of distractors between LAST and CLAST.
S7 File. Data of stroke patients in the acute-phase.
S8 File. Data of stroke patients in the non acute-phase.
S9 File. Sources of data and methods of assessment (measurement).
We are indebted to French artist Tristan Laville who helped us draw the replaced pictures.
12 / 14
Conceptualization: Hongyan Yang, Shenghua Tian, Constance Flamand-Roze, Ling Gao,
Wei Zhang, Yan Li, Jiajia Wang, Zhou Sun, Ying Su, Libin Zhao, Zhihou Liang.
Data curation: Zhou Sun, Ying Su, Zhihou Liang.
Formal analysis: Hongyan Yang, Shenghua Tian, Constance Flamand-Roze, Ling Gao, Wei
Zhang, Yan Li, Jiajia Wang, Zhou Sun, Ying Su, Libin Zhao, Zhihou Liang.
Investigation: Hongyan Yang, Shenghua Tian, Ling Gao, Wei Zhang, Yan Li, Jiajia Wang,
Zhou Sun, Libin Zhao, Zhihou Liang.
Methodology: Hongyan Yang, Shenghua Tian, Constance Flamand-Roze, Ling Gao, Wei
Zhang, Yan Li, Jiajia Wang, Zhou Sun, Ying Su, Libin Zhao, Zhihou Liang.
Project administration: Zhou Sun, Ying Su, Zhihou Liang.
Resources: Hongyan Yang, Shenghua Tian, Libin Zhao, Zhihou Liang.
Software: Hongyan Yang, Shenghua Tian, Ling Gao, Libin Zhao, Zhihou Liang.
Supervision: Zhou Sun, Ying Su, Zhihou Liang.
Validation: Zhou Sun, Ying Su, Zhihou Liang.
Visualization: Hongyan Yang, Shenghua Tian, Ling Gao, Libin Zhao, Zhihou Liang.
Writing ± original draft: Hongyan Yang, Wei Zhang, Yan Li, Jiajia Wang, Libin Zhao.
Writing ± review & editing: Hongyan Yang, Shenghua Tian, Constance Flamand-Roze, Ling
Gao, Zhou Sun, Ying Su, Zhihou Liang.
13 / 14
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