Understanding the Trail Making Test for Dementia

Doctor talking about the Trail Making Test
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What Is the Trail Making Test?

The Trail Making Test (TMT) is an evaluation tool that is sometimes used to screen for dementia by assessing cognition- the ability to think, reason and remember. The TMT has two parts that are referred to as the Trail Making Test Part A and the Trail Making Test Part B. The TMT is a timed test and the goal is to complete the tests accurately and as quickly as possible.

What Does Part A Consist of?

The TMT Part A consists of 25 circles on a piece of paper with the numbers 1-25 written randomly in the circles. The test taker’s task is to start with number one and draw a line from that circle to the circle with the number two in it to the circle with the three in it, etc. The person continues to connect the circles in numerical order until they reach number 25.

What Does Part B Consist of?

The TMT Part B consists of 24 circles on a piece of paper, but rather than all of the circles containing numbers, half of the circles have the numbers 1-12 in them and the other half (12) contain the letters A-L. The person taking the test has the more difficult task of drawing a line from one circle to the next in ascending order; however, he must alternate the circles with numbers in them (1-13) with circles with letters in them (A-L). In other words, he is to connect the circles in order like this: 1-A-2-B-3-C-4-D-5-E and so on.

How to Administer the Trail Making Test

To administer the test, give the test taker the paper with the circles on it, explain the directions and then demonstrate on a sample page how to complete Part A. Then, tell the person to begin the test and time them. Repeat the directions for Part B, again demonstrating on a sample page how to correctly complete Part B.

If the person is unable to complete the test after five minutes, you can discontinue the test.

What If the Test Taker Makes an Error?

When administering the TMT test, if an error is made, the administrator should tell the person right away and moves the pencil back to the last correct circle.

How Is the Trail Making Test Scored?

The Trail Making Test is scored by how long it takes to complete the test. If a person makes an error in the test, there’s no change in the score other than that it makes their completion time longer since the person has to go back to the previous circle, thus extending their time.

What Are Acceptable Scores for the Trail Making Tests?

According to the TMT directions for administration, an average score for the TMT Part A is 29 seconds and a deficient score is greater than 78 seconds.

For the TMT Part B, an average score is 75 seconds and a deficient score is greater than 273 seconds.

The results of the TMT were found to be influenced significantly by age; as people age, they require a longer time to complete the TMT.

How many years of education the person received only slightly impacted the results.

How Effective Is the Trail Making Test in Screening for Dementia?

The TMT measures attention, visual screening ability and processing speed, and is a good measure of overall cognitive functioning.

Part A is a good measure of rote memory. Part B is generally quite sensitive to executive functioning since the test requires multiple abilities to complete it. The TMT Part B has also been suggested as a useful tool to evaluate if a loved one with dementia can safely drive since it requires visual ability, motor functioning and cognitive processes.

The Oral Trail Making Test

The Trail Making Test can also be administered orally. Rather than giving the person a piece of paper and pen, you can simply ask the person to count from 1 to 25 (Part A). For Part B, the person is asked to verbally recite numbers and letters, alternating between numbers and letters like this: 1-A-2-B-3-C etc. The oral version of the TMT can be a quick tool to assess cognition when the person physically is unable to perform the written test or in situations like a hospital where illness and fatigue could affect the written results.

Pros and Cons of the Trail Making Test

Pros

It's free to use, while other tests require incur a cost each time they're administered.

It's brief, takeing only about five minutes to administer.

Part B has been shown to be a good measure of executive functioning. Tests that only measure memory or word-finding ability may miss impaired executive functioning and thus not detect some types of dementia.

Cons

Older age generally affects performance, even in the absence of any cognitive impairment, but this is not taken into account in the scoring.

Some research found that the TMT would exclude a significant number of capable drivers if it was solely relied upon to evaluate driving ability, while other studies found it missed other impairments that would endanger the driver or those around him.

As with any other cognitive test, the TMT is a screening test and should generally not be used in isolation to detect dementia.

Sources:

Archives of Clinical Neuropsychology. 19 (2004) 203–214. Trail Making Test A and B: Normative data stratified by age and education. www.usz.ch/non_cms/neurologie/HealthPro/Davos/normen_tmt.pdf

Cognitive and Behavioral Neurology. Clinical Validation of the Oral Trail Making Test. http://journals.lww.com/cogbehavneurol/Abstract/1996/01000/Clinical_Validation_of_the_Oral_Trail_Making_Test.7.aspx

National Highway Traffic Safety Institution. Physician’s Guide to Assessing and Counseling Older Drivers. http://www.nhtsa.gov/people/injury/olddrive/OlderDriversBook/pages/Chapter3.html

Papandonatos G, Ott B, Davis J, Barco P, Carr D. Clinical utility of the trail-making test as a predictor of driving performance in older adults. Journal of the American Geriatrics Society. 2015;63(11):2358–64. https://www.ncbi.nlm.nih.gov/pubmed/26503623.

State of Alaska. Department of Administration. Trail Making Test (TMT) Parts A & B. http://doa.alaska.gov/dmv/akol/pdfs/uiowa_trailmaking.pdf.

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