Age and Ageing 2006 35(3):304-306; doi:10.1093/ageing/afj090
© The Author 2006. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Inability to draw intersecting pentagons as a predictor of unsatisfactory spirometry technique in elderly hospital inpatients
SIR—The measurement of lung volumes by spirometry is one
of the cornerstones of the diagnosis, assessment and management
of asthma, chronic obstructive pulmonary disease (COPD) and
certain other respiratory diseases. Indeed, recent guidance
to medical practitioners in the United Kingdom has encouraged
the greater use of spirometry to detect COPD in the middle-aged
and elderly population [
1]. However, accurate spirometry requires
a sufficient level of co-operation and co-ordination on the
part of the patient even when attended by a skilled technician.
The criteria for a good technique were laid down by the American
Thoracic Society in 1994 and are generally known as the ATS94
criteria [
2]. These define minimum standards for the reliability,
reproducibility and completeness of the volume–time and
flow–volume curves generated during spirometry that can
be assessed by visual analysis of the curves and/or by computer
using dedicated algorithms. Although age is not an independent
predictor of a satisfactory spirometric technique, studies have
shown that older patients are often unable to meet the ATS94
standard, particularly when they have some degree of dyspraxia
or cognitive impairment [
3]. Of course, such impairments increase
in prevalence with age in the elderly population. One study
showed that very few patients were unable to perform spirometry
[
4], although that study did not include people above the age
of 73, whereas the real problem tends to be seen in patients
above the age of 80 [
3,
5]. As a consequence of this, spirometric
measurements on older people are often performed badly. Perhaps,
more seriously, they are not attempted because the attending
physicians expect the clinical information generated by the
tests to be inaccurate. Both these positions oversimplify the
issue and are not in the clinical best interests of this group
of patients. Previous work has shown that spirometry technique
and other techniques requiring co-ordination, such as the use
of inhalers, can be predicted with a high degree of accuracy
by performing tests of cognitive function, praxis and executive
function [
6,
7]. Some of those tests are time consuming and
are consequently too inconvenient to be used in routine clinical
practice. There is, therefore, a need to identify a quick screening
test to distinguish the patients who are likely to be able to
perform accurate spirometry from those in whom the testing would
be misleading or futile. A potential candidate is the intersecting
pentagon (IP) drawing component of the Mini-Mental State Examination
(MMSE) [
8]. This part of the MMSE is a test of understanding,
execution and co-ordination that might therefore be able to
discriminate between the two groups of patients. The main purpose
of this study was to explore the predictive power of IP in this
context and to compare IP with the entire MMSE.
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Methods
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We studied 80 patients (42 women) with a mean age of 84 years
(range 75–98). All were current or recent inpatients in
rehabilitation wards. For the purpose of this study, the patients
have been referred to as frail; this reflects their recent acute
illness, need for specialised geriatric rehabilitation and mean
Barthel ADL index score of 8 at the time of admission to the
ward. Inclusion criteria for the study were age 70 years or
more, requiring spirometry, willing to perform spirometry, willing
to perform the MMSE, willing to give written consent for the
data to be used for this research project and lack of exclusion
criteria. The exclusion criteria were advanced dementia (MMSE
<11), terminally ill, relapse of asthma or COPD not yet stable,
acute confusional state, dyspraxia demonstrated on neurological
examination, severe communication difficulties, vision or hearing
too poor to perform the tests, contra-indications to spirometry
such as recent eye surgery and lack of inclusion criteria. Patients
with severe dementia were excluded, on ethical committee advice,
because it would have been too difficult to confidently take
consent from them.
Spirometry was performed by one of the authors, after appropriate training, using a Microlabs 3000 portable spirometer. All patients made at least three attempts, and up to eight attempts were encouraged, if necessary. The spirometry data were stored electronically and as paper printouts for visual analysis. The ATS94 criteria were applied [2]. A separate observer performed the MMSE, and a photocopy of the IP was made for analysis. The IP was scored using the guideline for the MMSE, that is, it was considered adequate (IP+), if it consisted of two shapes each with five sides and five angles and had two angles overlapping. Those who did not meet that definition were scored IP–.
Statistical testing of categorical data was with Yates’ chi-squared test.
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Results
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We compared the patients’ ability to meet the ATS94 standards
with their MMSE score at the 23/24 threshold (an MMSE of <24
is usually considered to be indicative of cognitive impairment
and has been found to be a predictive threshold for the ability
to learn to use inhaler devices [
7,
9]) and with ability to
adequately copy the IP (IP+) or not (IP–). The results
are summarised in Table
1. We also calculated the sensitivity,
specificity and predictive values of the MMSE and IP as a predictor
of inability to meet the criteria (Table
2). Only 22% met the
full ATS94 spirometry criteria, although 67% were able to perform
a reliable FEV1.
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Table 1.. Comparison of Mini-Mental State Examination (MMSE) and intersecting pentagons (IP) scores in patients able and not able to meet the ATS94 criteria for spirometry
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Table 2.. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of a Mini-Mental State Examination (MMSE) <24 or inability to copy intersecting pentagons (IP–) in predicting the inability of a patient to meet the ATS94 criteria for adequate spirometry
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Discussion
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We have shown that almost all patients with an MMSE <24/30
and all who were unable to copy the IP diagram were unable to
perform spirometry to the standard required by the ATS94 criteria.
This finding is consistent with the observations on similar
patients attempting to learn to use inhaler devices [
7,
9] and
with the observation that cognitive impairment is an independent
predictor of an inadequate spirometry technique [
3]. However,
a large proportion of patients with an MMSE >23/30 (67%)
or who were able to copy the pentagons (68%) were also unable
to reach the stringent requirements of the strict ATS94 criteria.
This effectively limits the usefulness of MMSE and IP to the
prediction of inability to perform spirometry.
A large overall proportion (78%) of the group of patients studied could not do full spirometry. This contrasts with the finding of 6% of subjects unable to provide reliable spirometry data in a study of younger adults randomly selected from the community [4]. Our patients were much frailer physically and mentally, having been recruited from rehabilitation wards, and were more likely to have difficulties with executive function and subtle abnormalities of praxis. Although we did not specifically measure those functions for this study, we have found widespread abnormalities of that type in previous studies of patients recruited from the same environment [6, 7, 9].
There are clear clinical applications for the findings of this study. First, we have shown that about one in five of these frail and elderly patients can perform full spirometry, so in properly selected individuals, the test should be attempted to provide diagnostic and monitoring information. Interestingly, we also demonstrated that a larger proportion (67%) can reliably perform the measurement of FEV1. Although this is obviously of little value diagnostically, it might be of some use in tracking the response to treatment. Second, we have shown that the MMSE is useful for detecting patients who will probably not be able to perform full spirometry and that the IP drawing test has a specificity and positive predictive value which is at least as good as the whole MMSE in that regard and could therefore be used as a quick screening test for that purpose. The relatively low sensitivity of both tests would result in some patients being unable to perform spirometry despite passing the screen, although that would not be detrimental to an individual patient. In conclusion, cognitive screening with the MMSE and/or IP is a practical way to screen out frail elderly people who are unlikely to be able to provide reliable data from spirometric tests.
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Funding
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None.
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Key points
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- Patients who are unable to copy IPs are unlikely to be able to perform full spirometry.
- Patients with an MMSE <24/30 are also usually unable to perform full spirometry correctly.
- Most patients who are able to copy IPs can have their FEV1 measured reliably.
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Conflicts of interest
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None declared.
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Ethical approval
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Dorset Research Ethics Committee.
Stephen C. Allen1,* and
Pan Yeung2
1 Department of Medicine and Geriatrics, The Royal Bournemouth Hospital, Bournemouth, Dorset, UK Fax: (+44) 1202 704542 Email: stephen.allen{at}rbch.nhs.uk
2 Department of Medicine and Geriatrics, Princess Margaret Hospital, Lai Chi Kok, Kowloon, Hong Kong
* To whom correspondence should be addressed
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References
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- Bellia V, Pistelli R, Catalano F et al. Quality control of spirometry in the elderly – the SARA study. Am J Respir Crit Care Med 2000; 161: 1094–100.[Abstract/Free Full Text]
- Allen SC, Jain M, Ragab S, Malik N. Acquisition and retention of inhaler techniques require intact executive function in elderly subjects. Age Ageing 2003; 32: 299–302.[Abstract/Free Full Text]
- Allen SC. Competence thresholds for the use of inhalers in people with dementia. Age Ageing 1997; 26: 83–6.[Abstract/Free Full Text]
- Folstein FM, Folstein SE, McHugh PR. Mini-mental state: a practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975; 12: 189–98.[CrossRef][ISI][Medline]
- Allen SC, Ragab S. Ability to learn inhaler technique in relation to cognitive scores and tests of praxis in old age. Postgrad Med J 2002; 78: 37–9.[Abstract/Free Full Text]
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