Table 1.

Cognitive and Dual Task Assessments in Chronic Lung Diseases

Cognitive Assessment/Instrument	Brief Description of Assessment	Administration Time and Special Training	Limitations
Cognitive screening instrument
Montreal Cognitive Assessment41	A cognitive screening tool designed to identify the presence of mild cognitive impairment. A score of > 26 of 30 is considered normal in the general population	10 min	Consideration of educational level in those with lower/higher levels (floor and ceiling effects)
	Cognitive domains: Memory, language, executive function, visuospatial skills, calculation, abstraction, attention, concentration, and orientation	Training and certification are required	Cross-cultural limitations
Executive function, processing speed, or verbal fluency
Trail Making Test (Part A and Part B)42	Part A: Accurately connect 25 numbers that have been randomly placed and encircled in a specific order. Part B: Connect 25 randomly placed numbers and encircled letters, following an alternating alphanumeric sequence (eg, number-letter-number-letter). Scoring is based on the time (seconds) taken to complete each section. A shorter time indicates better performance	5 to 10 min	Part B has limitations in detecting cognitive switching in those with slow processing or reduced fluency with the English alphabet
	Cognitive domains: Measures processing speed (Part A) and processing speed with cognitive switching, an aspect of executive function (Part B)	Public domain
Verbal Fluency Test43	Evaluates the capacity to generate words starting with a particular letter (phonemic verbal fluency) or pertaining to a specific knowledge category (semantic verbal fluency). The total number of words named comprises the score	Usually 60 s per trial (total of 5 min depending on how many trials administered)	Cultural and language factors
	Cognitive domains: Measures verbal generativity and word access, with phonemic fluency particularly associated with frontal lobe generativity (an aspect of executive function)	No training required	Slow processing speed or reduced language fluency may affect phonemic fluency and not reflect limitations in executive function
Working memory, processing speed, attention, visual scanning, executive function
Digit Symbol Substitution Test44	Cognitive test that involves matching symbols to numbers with participants copying the symbol into spaces below a row of numbers. The score is calculated based on the number of correct symbols while timed	90-120 s	Lack of specificity in determining the precise cognitive domain that has been affected (eg, motor slowing vs psychomotor slowing)
	Cognitive domains: Measures psychomotor speed, attention, and visual scanning	No specialized training required
		Public domain
Clock-Drawing Test45	Requires the individual to draw a clock	No time limit	Not a sensitive instrument for subtle cognitive impairment
	Free-drawn method: The individual is asked to draw a clock from their memory	No training required
	Pre-drawn method: The participant is given a circular outline of a clock and then asked to fill in the numbers on the clock face and/or to draw the clock hands at a fixed time	Public domain and widely available
	Cognitive domains: Measures planning, memory, visuospatial ability, neglect, attention, and symbolic representation
Dual task (ie, backward spelling or counting)21	Dual-task interference involves performing a cognitive task while doing a motor task	Spelling backward	Non-English-speaking individuals may find it difficult to spell English words backward
	Cognitive domains: Attention, working memory	Less than 1 min	May not provide a reliable measure of change over time
	Spelling backward: Example can include spelling a 5-letter word backward	The duration of counting backward is variable based on test
	Backward counting: A cognitive task requiring counting backward from one number to another (ie, 50-1, 100-1). A point is given for each correct answer	No training required
	Cognitive domains: Attention, memory, executive function
Digit Span12	The task involves asking participants to repeat a sequence of numbers that gradually increases in length	Varies depending on performance (approximately 1-3 min)	The presenter’s pronunciation, including clarity, pitch, and rhythm, can affect the scores
	Digit span forward: Participants are instructed to recall the numbers presented in the same order	No training required
	Digit span backward: Recall numbers in reverse order
	Total correct score determined by adding the number of correctly reported lists from both the forward span and the backward span
	Cognitive domains: Working memory and attention
Reasoning and problem solving
Culture Fair Intelligence Test46	Nonverbal skills that define a person’s general intelligence minimizing sociocultural or environmental influence	Varies by tests used (approximately 12-18 min per section)	Not widely used
	Forms A and B with 4 subtests: Series, classification, matrices, and condition.	No training required	Long administration time
	Each subtest is scored by counting the number of correct responses
	Cognitive domains: Fluid intelligence, reasoning, and problem solving