Short IQCODE: 16-item informant questionnaire

What this assessment is

The Short IQCODE is a 16-item informant questionnaire that compares an older person's everyday cognitive ability with 10 years earlier; complete ratings yield a mean from 1 to 5, where 3 means no average change and higher scores mean greater reported decline. Published thresholds of 3.31 and 3.38 are screening choices, not diagnoses or severity bands.

Its full name is the Short Form of the Informant Questionnaire on Cognitive Decline in the Elderly.

The Short IQCODE screens for possible decline. It does not diagnose dementia or identify its cause.

Who it was designed for

The questionnaire is completed by a relative, friend, or another informant who has known the person for at least ten years.

That long view is central to the measure. The Short IQCODE asks about change within one person, not whether the person performs like other people of the same age.

It can be useful when education or premorbid ability makes one-time cognitive testing hard to interpret. It still depends on a knowledgeable informant and a suitable language version.

This page covers the 16-item short form. The original long IQCODE and modified versions need their own scoring rules.

How it is administered

The informant gives one 1-to-5 rating for each of 16 comparisons between current performance and performance ten years ago.

Lower ratings represent improvement, 3 represents no change, and higher ratings represent decline.

The informant should answer from observed experience. Guessing about activities they rarely see can reduce the value of the result.

Use all 16 responses for the standard mean. The official short-form resource does not give a general rule for creating a score from an incomplete form.

What it measures

The Short IQCODE focuses on changes that depend on memory and other cognitive abilities in daily life.

It does not ask the person to complete a timed cognitive task. This reduces the effect of performance anxiety on the day, but it adds dependence on the informant's recall and judgment.

The AD8 is a shorter informant screen that counts eight reported changes. MoCA 8.1 and SLUMS directly sample cognitive performance.

Informant report and direct testing answer different questions.

How scoring works

Add the ratings for all 16 items. Divide the sum by 16.

The resulting mean ranges from 1 to 5:

• a mean below 3 indicates average improvement
• a mean of 3 indicates no average change
• a mean above 3 indicates average decline

Use the mean, not the raw sum, when comparing a result with published IQCODE thresholds. Do not replace missing answers with 3 or divide by 16 when fewer than 16 valid responses were recorded unless a validated protocol tells you to do so.

How to interpret a Short IQCODE score

There is no single cutoff that works best in every population and setting.

The official Australian National University resource discusses 3.31 and 3.38 as two possible screening thresholds. Studies have also tested other values.

A result above the selected threshold is a positive screen for possible cognitive decline. It is not a mild, moderate, or severe category.

Choose a threshold before interpreting the result. The choice should match the population, language, setting, and purpose. A threshold selected to avoid missed cases will usually create more false positives.

Review the number with the pattern and course of reported change.

What the score cannot tell you

The Short IQCODE cannot diagnose dementia, identify a cause, or show which cognitive domain is impaired.

It cannot distinguish gradual neurodegenerative change from the effects of stroke, delirium, depression, medicine, substance use, sleep problems, sensory loss, or another medical condition.

The ten-year comparison can also be difficult when the person's health, work, language use, or daily responsibilities changed substantially during that period.

A lower mean does not rule out a recent or subtle problem. A higher mean does not prove progressive disease.

Evidence and limitations

A.F. Jorm developed the 16-item short form from the longer IQCODE in 1994.

A Cochrane review found that IQCODE accuracy varied across thresholds and settings. The review supports its use as a screen, not as a stand-alone diagnosis.

The measure's strength is comparison with the person's own earlier ability. Its limitation is that the comparison comes through another person's memory and perspective.

Note the exact form, informant relationship, language, and chosen threshold with the result.