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Conditions associated with an abnormal nonspecific pattern of pulmonary function tests
Robert E Hyatt1, Clayton T Cowl1, Julie A Bjoraker1
1Department of Internal Medicine, College of Medicine, Mayo Clinic, Rochester, MN.
Chest
|September 25, 2008
Summary
A common abnormal pulmonary function test pattern, the nonspecific pattern (NSP), is often linked to airway disease or restricted lung expansion. Further investigation is needed for consistent diagnosis.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
Background:
- A frequent abnormal pulmonary function test (PFT) pattern, termed nonspecific pattern (NSP), is characterized by reduced FEV1 and FVC with normal FEV1/FVC ratio and total lung capacity.
- The underlying causes and mechanisms of this common PFT finding remain largely unknown.
Purpose of the Study:
- To identify medical conditions associated with the nonspecific pattern (NSP) of PFT results.
- To explore potential mechanisms contributing to the development of the NSP.
Main Methods:
- A random sample of 100 subjects with the NSP was selected from a database of 80,929 PFT results.
- Medical records and all available diagnostic tests for the selected subjects were reviewed.
Main Results:
- Airway hyperresponsiveness (AHR) and obesity were frequently observed in subjects with the NSP.
- Two groups were identified: Group A (68 subjects) showed evidence of airway disease (including AHR and chronic lung disease), potentially explained by a volume derecruitment model.
- Group B (32 subjects) had no evidence of airway disease; restricted thoracic or lung expansion may explain their NSP. Test results were inconsistently nonspecific in 70% of subjects with repeat testing.
Conclusions:
- Airway disease is the probable cause of the NSP in the majority (68%) of subjects studied.
- Restricted expansion of the thorax or lung is implicated in the remaining subjects (32%) with the NSP.
- The NSP may not represent a stable physiological state, as indicated by inconsistent results upon repeat testing.
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