Does a 42-year-old female with decreased mid flows on spirometry, but otherwise normal results, need to be referred for further evaluation?

From the Guidelines

A 42-year-old female with isolated decreased mid flows on spirometry but otherwise normal results generally does not require immediate referral for further evaluation. This finding alone, when pulmonary function tests show normal FEV1, FVC, and FEV1/FVC ratio, is often a nonspecific finding that may represent early small airway dysfunction but is not diagnostic of any specific condition 1. The patient should have her spirometry repeated in 6-12 months to monitor for any progression of abnormalities.

Key Considerations

• In the interim, it would be appropriate to assess for respiratory symptoms such as cough, wheezing, or exertional dyspnea, and to review risk factors including smoking history, occupational exposures, and family history of lung disease.
• If the patient develops symptoms, shows worsening on follow-up spirometry, or has significant risk factors, referral to a pulmonologist would then be warranted.
• The decreased mid flows (FEF25-75%) represent airflow in the middle portion of forced expiration and may be the earliest indicator of small airway disease, but this measurement has high variability and lower reproducibility than other spirometric parameters, making it less reliable as a standalone diagnostic indicator 1.

Clinical Approach

• According to the GOLD 2025 report, airflow obstruction should be identified using the FEV1/FVC ratio, but if there is a strong clinical suspicion of COPD and the FEV1/FVC ratio is normal, further follow-up and investigations, which could include assessment of the FEV1/SVC ratio, are recommended 1.
• The 2022 ATS/ERS technical standard on interpretation of routine lung function tests acknowledges that the use of SVC is more sensitive but less specific and adds complexity to lung function testing 1.
• Measurement of lung volumes is not mandatory to identify an obstructive defect, but it may help to disclose underlying disease and its functional consequences 1.

From the Research

Spirometry Test Results Interpretation

The user's question revolves around the interpretation of spirometry test results for a 42-year-old female with decreased mid flows but otherwise normal results. The key issue here is understanding what decreased mid flows indicate and whether this necessitates a referral for further evaluation.

Decreased Mid Flows on Spirometry

• Definition and Implication: Decreased mid flows, often measured as Forced Expiratory Flow (FEF) between 25% and 75% of the forced vital capacity (FVC), can indicate obstruction in the small airways. This parameter is sensitive to early airway disease and can be abnormal even when other spirometric measures like FEV1 and FVC are within normal limits 2.
• Clinical Significance: The presence of decreased mid flows in an otherwise normal spirometry suggests the possibility of early or mild airway obstruction. This could be due to various conditions, including asthma, chronic obstructive pulmonary disease (COPD), or other respiratory diseases.

Need for Referral

• Guidelines and Recommendations: The decision to refer a patient for further evaluation should be based on clinical judgment, considering symptoms, risk factors, and the results of the spirometry test. For patients with abnormal spirometry results, including those with decreased mid flows, further testing such as a methacholine challenge test may be indicated to assess airway responsiveness 3.
• Methacholine Challenge Test: This test is used to assess airway hyperresponsiveness, a hallmark of asthma. However, a negative test does not entirely rule out asthma or other conditions, and a positive test can be seen in conditions other than asthma [3, @9@].
• Consideration of Other Factors: The interpretation of spirometry results should also consider the lower limit of normal (LLN) for the parameters measured. The LLN is crucial for accurately diagnosing airway obstruction, especially in older adults or those with risk factors for COPD 4, 5.

Conclusion on Referral Necessity

Given the decreased mid flows on spirometry, even with otherwise normal results, it would be prudent to consider further evaluation to determine the cause of this abnormality. This could include a detailed medical history, physical examination, and potentially additional pulmonary function tests like the methacholine challenge test, depending on the clinical context and symptoms presented by the patient.

Key Points for Consideration

• Decreased mid flows on spirometry can indicate small airway obstruction.
• Further evaluation, including a methacholine challenge test, may be necessary to assess airway responsiveness.
• Interpretation of spirometry results should consider the LLN and clinical context.
• A holistic approach, considering all spirometric measures and clinical factors, is essential for accurate diagnosis and management.