From the Guidelines
When FVC and FEV1 are more than 2 standard deviations above the predicted z-score, this indicates supranormal lung function, which is generally not concerning and typically doesn't require any specific treatment or intervention. This finding can be seen in individuals with excellent respiratory health, particularly athletes or those with larger than average lung volumes relative to their body size, as noted in the American Thoracic Society technical statement 1. The z-score is a standardized measurement that compares an individual's lung function to population norms, accounting for factors like age, height, sex, and ethnicity. A z-score greater than +2 means the values are significantly higher than expected for that person's demographic characteristics.
According to the recommendations for a standardized pulmonary function report, only FVC, FEV1, and FEV1/FVC need to be routinely reported, as they provide the most clinically useful information 1. While unusually high lung function values should be verified for technical accuracy during the pulmonary function test, they rarely indicate pathology. In some cases, very high values might reflect measurement error or improper calibration of testing equipment. If the testing was performed correctly, these results simply suggest excellent respiratory capacity and efficient lung mechanics, which is generally considered advantageous for overall health.
Key points to consider in the interpretation of these results include:
- The normal limit(s) of each test value, with the measured value shown before reference values, ranges, or normal limits 1
- The displacement of the result from a predicted value in standard deviation units (z-score) to help in understanding abnormality 1
- The potential for measurement error or improper calibration of testing equipment, which should be ruled out before concluding that the high values are genuine.
From the Research
FVC and FEV1 More Than 2 SD Above Predicted Z-Score
- There are no research papers provided that directly address the question of FVC and FEV1 being more than 2 SD above the predicted z-score.
- The provided studies focus on the diagnosis and severity classification of chronic obstructive pulmonary disease (COPD) using spirometry measurements such as FEV1, FVC, and the FEV1/FVC ratio 2, 3, 4, 5, 6.
- These studies discuss the interpretation of pulmonary function tests, including the use of FEV1 and FVC to diagnose obstructive and restrictive lung diseases, but do not provide information on what it means for these values to be more than 2 SD above the predicted z-score.
- The studies do provide information on the use of z-scores and percent predicted values to interpret spirometry results, but this information is not directly relevant to the question of FVC and FEV1 being more than 2 SD above the predicted z-score 2, 5.