Pulmonary Function Test Quality in the
Elderly – A Comparison with Younger Adults
Respir Care 2014;59(1):16-21.
Gregg Ruppel, MEd, RRT, RPFT, FAARC
Adjunct Professor
Pulmonary, Critical Care and Sleep Medicine
Saint Louis University School of Medicine
Research Question
Can elderly patients achieve quality scores for
spirometry and DLco comparable to a younger
adult population?
Why this is important:
1. Spirometry and DLco both involve elements of patient effort and cooperation
to provide valid data
2. Spirometry and DLco each have significant evidence-based indications related
to evaluation of lung function
3. The population is ageing
Background Literature
Refs 1 - 11
• Mini Mental State Examination (MMSE)
commonly used to grade cognitive
impairment
– <17 severe impairment, 18-24 mild, 24-30 normal
– Patients WITH cognitive dysfunction have
difficulty performing spirometry
Background Literature
Refs 1 - 11
• Most elderly subjects without cognitive
dysfunction can perform acceptable
spirometry
– Acceptability and reproducibility of spirometry
ranges from ~70 – 95%
– FEV1 tends to be more repeatable in the elderly
– Age itself does not appear to be a limiting factor
– Misdiagnosis of COPD & asthma common
Background Literature
Refs 1 - 11
• DLCO acceptability/repeatability in the elderly not
well documented
– Younger age may be predictive of poor quality
(unable to inspire maximal IVC)
• Most studies of spirometry and DLCO quality
used older standardization recommendations
Methods
• Retrospective review (22 months)
– All patients (elderly & younger) included
– Elderly: > 80 years
– Controls: ages 40-50 years
• Sample size dependent on time frame
– Post hoc power analysis
• Sources of bias: hospital based PFT lab
Methods
• Data quality
– ATS/ERS 2005 recommendations to assess quality
– Software QA grading system used
– Over-read by chief technologist
– Lab QA included monthly/quarterly tech feedback
– Equipment QC and biologic controls within limits
• Predicted values
– GLI (ages 3-95) used for % predicted and LLN
Percent Predicted vs LLN
LLN = 5th centile; using 80% introduces age-related bias
Quanjer et al, Eur Resp J Epub 2012
Methods
• Statistical Analysis
– Categorical data: Fisher’s exact test
– Continuous variables:
• Student t-test unpaired means
• Mann-Whitney U test unpaired medians
– Data reported as mean±SD or median
w/interquartile ranges
– Two-tailed p <0.05 significant
– Post hoc power analysis
Spirometry QA (fig. 1)
DLCO QA (fig. 1)
Results
Demographics
Results
Spirometry
Elderly (n=150)
Control(n=178)
p
Results
DLCO
Elderly (n=150)
Control(n=178)
p
Results
Spirometry & DLCO Quality
Results
• Most common reason for spirometry test
failure (elderly and controls): exhalation < 6
seconds and/or BEV > 5%
• Most common reason for DLCO test failure:
not stated (inability to inspire 85% of VC)
• Post hoc power analysis – generally not useful
but may explain why no significant differences
were observed
Discussion
• Under-diagnosis, over-diagnosis, and
misclassification are all problems related to
elderly
• Asthma and COPD are common problems,
amenable to treatment if properly diagnosed
• Elderly patients WITHOUT cognitive
impairment can perform spirometry and DLCO
acceptably and reproducibly
Discussion
What this study adds
• Acceptability/repeatability for spirometry and
DLCO are similar for elderly (notably >80
years) and younger subjects
• High levels of data quality are achievable using
procedures that strictly adhere to current
ATS/ERS guidelines AND utilizing a laboratory
QA program
• Data with B or C quality scores are useable
Discussion
Potential study limitations
• Bias associated with:
– Lack of diversity (race)
– Hospital lab referrals (lung dysfunction?)
– Cognitive impairment not evaluated
– Equipment (software grading of test quality)
– Technologist skill/experience/motivation
Take Home Message(s)
• Elderly subjects can perform acceptable and
repeatable spirometry and DLCO similar to
younger subjects
• A comprehensive lab QA program likely
contributes to high rates of acceptable tests
• Predicted sets need to be carefully selected,
particularly when elderly subjects are being
evaluated
Editorial Comments
• An editorial from Sorensen accompanies the
Haynes paper and makes 2 important points
– Misdiagnosis and/or misclassification of asthma
and COPD in older subjects can be reduced by
good quality PFTs
– Readmission of patients with COPD has real world
consequences ($$) and better diagnostics (PFTs)
should help to improve disease management
Thanks!
Gregg Ruppel, Med, RRT, RPFT, FAARC
ruppelgl@slu.edu