The IHDS may be a useful screening test to identify individuals at risk for HIV dementia.
It consists of three subtests: timed finger tapping, a timed alternating hand sequence test, and the ability to recall four items at 2 minutes.

1. The number of finger taps of the first two fingers of the non-dominant hand is measured by instructing the participant to open and close their fingers as widely and as quickly as possible over a 5-second period.

2. In the alternating hand sequence test, individuals are asked to perform the following movement with the non-dominant hand as quickly as possible over a 10-second period: (i) clench the hand in a fist on a flat surface; (ii) put the hand flat on the surface with the palm down; and (iii) put the hand perpendicular to the flat surface on the side of the 5th digit. The participant is then asked to perform the sequence correctly twice, for practice, before the 10-second subtest is performed. The number of sequences correctly performed up to a maximum of 4 is scored.

3. The ability to recall is measured by reciting 4 words to the subject, then asking him or her to repeat the words immediately. The words are repeated by the examiner until the subject can repeat back all 4 words correctly. The subject is then asked to recall the 4 words after the timed finger tapping and the alternating hand sequence tests are performed. The number of items recalled is scored as 1 point for each word. A half-point is assigned for each correct word recalled after prompting.

A total score out of 12 is calculated for each participant, with each subtest contributing up to a maximum of 4 points to the total score.

Sacktor NC et al . The International HIV Dementia Scale: a new rapid screening test for HIV dementia. AIDS 2005;19(13):1367-74.