Neurocognitive Evaluation:
Neurocognitive testing was conducted in dedicated evaluation rooms,
where the testing enviornment was free of distractions and both the
examiner and examinee were comfortable. The Indian adaptation of
Wechsler Intelligence Scale for Children-Fourth
Edition(WISC-IVINDIA) was used for the assessment of
neurocognitive deficits9. This is a valid, reliable
and individually administered comprehensive clinical instrument for
assessing the cognitive ability of children aged between 6 years 0
months to 16 years 11 months and is available commercially.
WISC-IVINDIA assesses four primary domains of
cognition, using 15 subtests, which represent a childs abilities in more
discrete cognitive domains. The scores of the four domains are
integrated to generate the Full Scale Intelligence Quotient(FSIQ), that
represents a child’s general intellectual ability.
Before the start of study, training about the
WISC-IVINDIA scale was obtained from the Child
Psychologist, who supervised the assessments and was a co-investigator.
During the study, one fifth of the assessments were randomly
cross-checked by the Psychologist.
As per WISC-IVINDIA the first cognitive domain
assessed is the Verbal Comprehension Index(VCI), using subtests on
Vocabulary(VC), Comprehension(CO), Word reasoning(WR), General
knowledge(Information, IN) and finding similarities(SI). The second
domain assessed is Perceptual Reasoning, which is the ability of a
person to draw upon visual-motor and visual-spatial skills, organize
their thoughts, create solutions, and then test them. The Perceptual
Reasoning Index(PRI) is assessed by Block designing(BD), Picture
conceptualization(Picture concepts, PC), Matrix reasoning(MR) and
Picture completion(PCm). The third domain tested is the Working Memory
Index(WMI). Participants are assessed on their ability to repeat numbers
in order(Digit Span, DS), read a sequence of numbers and
letters(Letter-number sequencing, LN) and mentally solve arithmetic
problems(Arithmetic, AR). The fourth and final domain evaluated is
processing speed which tests the childs ability to focus their
attention, quickly scan and discriminate between objects and put them in
order sequentially. The Processing Speed Index(PSI) is calculated by
drawing symbols in corresponding shapes(Coding, CD), searching for
symbols(Symbol Search, SS) and marking and cancelling targeted
pictures(Cancelling, CA).
There are 10 primary and 5 supplemental subtests. The primary sub tests
are vocabulary, comprehension, finding similarities, block designing,
picture conceptualisation, matrix reasoning, digit span, letter-number
sequencing, coding, and symbol search(10 total). Two subtests were
administered to obtain each of the primary index scores. FSIQ was
derived from 8 of the 10 primary subtests. Acceptable substitutions as
per WISC-IVINDIA manual were taken. Hence, for the
purpose of this study, subtests selected for assessment of FSIQ were
directed at assessing comprehension, similarities, picture completion
and picture conceptualisation, digit span, arithmetic, coding and
cancellation. Each subtest provided a ‘Raw Score’. These ‘Raw Scores’
were converted into a ‘Scaled Score’ using the
WISC-IVINDIA manual based on the exact chronological
age, using the Date of Birth or age in completed years as remembered by
the guardians. Each primary index domain was derived from the sum of
scaled scores.
The FSIQ was obtained from the four primary index scores. The prevalence
of neurocognitive deficits was calculated based on this FSIQ, with
presence of neurocognitive deficits taken at a FSIQ of <90.
Spectrum of deficits was analysed by calculating the prevalence of
deficits in each of the 4 primary index scores. Any score less than 90
was considered as a deficit in that particular domain. A structured
record form was used to document all assessment details, scores and
calculations.
Statistical Analysis: The data was analysed using with STATA
14.2 software. Categorical data was tested by the Chi-square or Fischer
extract test and presented as percentage or proportion. Continuous data,
which was normally distributed, was presented as Mean ± Standard
Deviation(Mean ± SD) and the data which is not normally distributed is
presented as Median with corresponding Inter-Quartile Range(Median +
IQR). The prevalence of neurocognitive deficits in the sample population
was calculated in percentage, including complete and individual demain
deficits. The various factors associated with neurocognitive deficits in
sample population was also assessed using multiple logistic regression
analysis. Odds ratio was calculated along with 95% confidence interval.
In all analysis, p value <0.05 was considered to represent a
statistically significant difference.