Pulmonary Function Test Quality in the Elderly – A Comparison with Younger Adults

Respir Care 2014;59(1):16-21.

Gregg Ruppel, MEd, RRT, RPFT, FAARCAdjunct Professor

Pulmonary, Critical Care and Sleep MedicineSaint Louis University School of Medicine

Research QuestionCan 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 data2. Spirometry and DLco each have significant evidence-based indications related

to evaluation of lung function3. The population is ageing

Background LiteratureRefs 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 LiteratureRefs 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 LiteratureRefs 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

Quanjer et al, Eur Resp J Epub 2012

LLN = 5th centile; using 80% introduces age-related bias

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)

ResultsDemographics

ResultsSpirometry Elderly (n=150) Control(n=178) p

ResultsDLCO Elderly (n=150) Control(n=178) p

ResultsSpirometry & DLCO Quality

• 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

Results

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

DiscussionWhat 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

DiscussionPotential 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, FAARCruppelgl@slu.edu