Diagnosing dementia: is a questionnaire (IQCODE) good enough?

In a blog for members of the public and the professionals who care for them, Terry Quinn and Jenni Burton summarise the findings of a series of Cochrane Reviews describing a structured questionnaire that is used to help identify possible dementia. The questionnaire is called the IQCODE (Informant Questionnaire for COgnitive Decline in the Elderly). 

Page last updated 28 April 2022; page last checked 10 March 2023

Receiving a diagnosis of dementia is a life-changing experience. Patients and their families rightly expect that if this diagnosis is made, then the diagnosis is correct. However, making a diagnosis of dementia is not easy and many with the early stages of the disease remain undiagnosed. A dementia diagnosis should always be made by a trained professional based on the person’s symptoms, signs and the results of tests. These tests can range from sophisticated brain scans to more simple pencil and paper memory tests. Dementia involves progressive changes in memory and thinking. Sometimes these changes are not obvious to the person affected and so, useful information can come from family, friends or carers. Structured questionnaires have been created that ask informants about changes that could signify dementia. The most commonly used of these is the Informant Questionnaire on Cognitive Decline in the Elderly, or IQCODE for short.

The usefulness of tests for dementia will depend on the context in which the test is being administered. In the Cochrane Dementia Group we were keen to assess how dementia tests performed in a variety of different health care settings. To illustrate our reviews on IQCODE we thought we would tell the story of one person’s dementia diagnosis journey. So, let’s consider Mrs Cochrane…..

Mrs Cochrane is a 72 year old retired librarian. She lives in a bungalow with her partner Mr Cambell. They keep in relatively good health and enjoy a busy social life.

IQCODE for diagnosis of dementia in the community

A young researcher at the door

Mrs Cochrane is an engaged citizen scientist, who has been enjoying helping with online activities such as the Cochrane Crowd initiative. Mrs Cochrane pays a visit to the website that shares her name and finds that the Cochrane Dementia Group has a review on the usefulness of IQCODE when used with older adults living at home, Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the detection of dementia within community dwelling populations (July 2021).

In this particular review there are eleven studies including 2644 individuals. Many of the review findings are reassuring. A short (16-question) version of IQCODE seems just as good at diagnosing dementia as the original, longer (26-question) version – the less time filling out questionnaires the better. As she lives in a multicultural area, she was also pleased to see that IQCODE is available for use in various languages and the language used for assessment does not seem to compromise the accuracy of the questionnaire.

However, she is surprised that the studies included in the review use IQCODE in different ways. In particular it seems that there is no consensus on the IQCODE score that signifies a ‘positive’ test. She also notes that although the studies were all carried out in ‘community settings’, many have a particular focus on selected groups of people, for example people who have survived a stroke. With this in mind she is careful about how she interprets the summary of IQCODE accuracy.

The review suggests that in a group of people with dementia, IQCODE would make the correct diagnosis in about 80%. Mrs Cochrane is concerned about what might happen to the incorrectly diagnosed. What if she were the one in five people with a ‘positive’ IQCODE score who did not actually have dementia? The thought of having to go to a clinic for more memory tests or scans was a worry. She decided that when the researchers returned tomorrow she would help with their questionnaire but not ask Mr Campbell to complete the IQCODE section.

IQCODE for diagnosis of dementia in primary care

Later that year Mrs Cochrane attends her General Practice surgery for a medication review. After the consultation, the doctor asks: “While you’re here Mrs Cochrane, would you mind taking home this questionnaire (IQCODE) for your partner to complete?” The doctor explains that the surgery had been identified as having a low rate of dementia diagnosis. To improve things they were targeting older people attending the surgery to try and diagnose early memory problems. “It’s a simple questionnaire and may help put your mind at rest”.

Mrs Cochrane accepts the questionnaire, but her mind is far from restful. She again investigates the evidence around IQCODE and finds the Cochrane review looking at IQCODE in primary care, Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the detection of dementia within a general practice (primary care) setting (July 2021).

There was only one study and this was conducted in Hawaii. Mrs Cochrane wonders if a study concerned with Japanese Americans would be relevant to her situation. With only one published study, the Cochrane reviewers were unable to provide any guidance on the usefulness of the IQCODE in General Practice. She decides that, on balance, it may be best not to complete the IQCODE. Rather, she encourages Mr Campbell to dig out the passports, as a trip to Hawaii sounds very appealing.

IQCODE for diagnosis of dementia in secondary care

A couple of months later Mrs Cochrane has a fall in the garden. Mr Campbell phones an ambulance and they are taken to the local hospital. While Mrs Cochrane has x-rays, Mr Campbell is approached by a doctor who wants to “ask a few questions about your partner’s memory”. The doctor explains that it is hospital policy that everyone aged over 65 is assessed for memory problems and so an IQCODE is completed. A couple of weeks later Mrs Cochrane receives a letter inviting her to attend the outpatient Memory Clinic to follow-up on her ‘abnormal’ IQCODE results. She curses Mr Campbell and goes straight online to check out the Cochrane review of IQCODE in a hospital setting: Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the detection of dementia within a secondary care setting (July 2021).

The review collates information from 13 studies, totalling 2745 people. In common with the other IQCODE reviews, Mrs Cochrane decides that not all the included studies are directly relevant to her situation. Interestingly, IQCODE seems to perform better when used in general settings, than when used in specialist memory wards. She also notes that the review authors questioned the quality of a number of the included studies. In particular, certain studies may have preferentially selected patients for whom IQCODE would work well.

Accepting these caveats, she carefully reads the summary analyses in the review. When used in hospital, IQCODE seems good at picking up people with dementia but it runs the risk of also picking up (and misdiagnosing) many people who do not have the condition. In hospitals the IQCODE may be most useful when the result is negative as this helps ‘rule out’ possible dementia. So, although she has a ‘positive’ IQCODE it was still very possible that Mrs Cochrane did not have dementia.

One month later, Mrs Cochrane has completed in-depth memory assessments with a psychologist; has undergone an MRI brain scan and a series of blood tests. At the memory clinic the Consultant reassures her that her memory is in good health, in fact her memory and thinking were better than most people of her age. “It is probably all that online Cochrane Crowd work that you do” remarks the Consultant. Of course, Mrs Cochrane is familiar with the Cochrane reviews of treatments to prevent dementia and she knows that there is no good evidence (yet) that online activity maintains memory.

No dementia test is perfect

Mrs Cochrane’s story is fictional, but the issues raised are very real. No dementia test is perfect and thought must be given to the implications of a ‘false positive’ or ‘false negative’ result. These issues are particularly relevant in countries that are instituting primary care ‘case finding’ or hospital based screening.

The lack of information on the use of IQCODE in primary care is a particular concern as arguably the test is well suited to this setting and increasingly General Practitioners are being asked to look for dementia. The papers included in the Cochrane reviews focus on the accuracy of IQCODE. To get a complete picture of how well the test works it would be useful to see research on other aspects of IQCODE, such as feasibility (can the test always be completed, do people always have an informant); acceptability (do people want the test, what do they understand about the test) and economics (what are the emotional, financial and time related costs of misdiagnosis).

IQCODE is only one a number of tests used to help clinicians make a dementia diagnosis. For those interested in the area, the Cochrane Dementia group are working to summarise the accuracy of all the various tests available. 

More blogs about diagnosing dementia

Dementia diagnosis: a decade of evidence

Detecting dementia: how hit and miss is this questionnaire?

Do join in the conversation on Twitter with @DrTerryQuinn @JenniKBurton  and @CochraneUK #dementiaspotlight or leave a comment on the blog.

References (pdf). Click author names to see biographies.

Please note, we cannot give specific medical advice and do not publish comments that link to individual pages requesting donations or to commercial sites, or appear to endorse commercial products. We welcome diverse views and encourage discussion but we ask that comments are respectful and reserve the right to not publish any we consider offensive. Cochrane UK does not fact check – or endorse – readers’ comments, including any treatments mentioned.

Terry Quinn reports grants from The Stroke Association, from null,  outside the submitted work. Jenny Burton has nothing to disclose.

Diagnosing dementia: is a questionnaire (IQCODE) good enough? by Terry Quinn

is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International

1 Comments on this post

  1. Excellent treatment of a currently very relevant area – and in a genuinely original way!

    Any tool is only as good as its user. There is always the danger encapsulated in the aphorism: “To a man with a hammer, everything is nail-shaped.” In other words, as you imply, context is everything.

    As a (largely retired) geriatrician, I frequently face older patients on the ward who have presented with a crisis, and in whom for various reasons I am very suspicious of a (hitherto undiagnosed, or even suspected) dementia illness being present.

    In this situation I find IQCODE invaluable as a tool to achieve several ends: It allows anyone in the MDT to obtain a structured and focused collateral history; It allows a conversation with the family to introduce the idea that a dementia illness (with or without added delirium) might be present – not infrequently confirming their already growing suspicions; It gives a good reason to support a formal referral to the memory clinic; Finally, it gives a benchmark to allow subsequent assessment to be compared against in the future, should problems persist, or worsen.

    In this circumstance, Jackson’s paper [1] gives me confidence that the results (& PPV) are robust enough to rely on for the above purposes – even with coexisting delirium.

    The EBM triad described by Sackett [2] mandates the involvement of a (wise) clinician, in addition to good evidence and awareness of the patient’s preferences. A patient (or relative) might use this tool wisely in just the same way that they might use a scalpel wisely, but on the other hand…!

    Your examples illustrate brilliantly how evidence cannot be used ‘in vacuo’, but needs to be assessed in context, knowing (and understanding!) its performance characteristics.

    This blog also illustrates the ethical complexities of dealing with a patient whose insight may (or not) be impaired, of dealing with an advocate for the patient (especially difficult when the relationship is not legally specified with a Power of Attorney), and of keeping promises made in good faith to an individual in a system so disjointed that even simple facts and decisions rapidly can become lost.

    1. Delirium as a marker of undiagnosed dementia in the general hospital: Evaluation of pragmatic methods of screening and follow-up
    Jackson, TA (2016) Ph.D. thesis, University of Birmingham

    2. Evidence based medicine: what it is and what it isn’t. Sackett DL, et al BMJ 1996; 312 (7073): 71-72

    Kit Byatt / Reply

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