新方法定义COPD患者受损肺功能

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Novel method for defining impaired pulmonary function in COPD

MedWire News: A novel method for defining impaired pulmonary function is associated with a statistically significant increase in the risk for death and the likelihood of having respiratory symptoms, US research shows.

These at-risk individuals were identified using the lambda-mu-sigma (LMS) method to define the lower limit of normal for the FEV1/forced vital capacity (FVC) ratio.

This method is less likely to overdiagnose chronic obstructive pulmonary disease (COPD) and could lead to a more targeted use of COPD-specific pharmacotherapy, say Carlos Fragoso (Yale University, New Haven, CT) and colleagues in the American Journal of Respiratory and Critical Care Medicine.

The lambda-mu-sigma (LMS) method is a novel approach that defines the lower limit of normal (LLN) for the ratio of FEV1/FVC as the fifth percentile of the distribution of Z-scores.

Past studies suggest that this method more accurately describes the relationship between spirometric lung function and predictor variables across the lifespan.

To test the clinical validity of this method in COPD, the researchers used data from a sample of 3502 white Americans aged 40 to 80 years old. They stratified the FEV1/FVC according to the LMS-LLN, with thresholds set at the 5th, 10th, 15th, 20th, and 25th percentiles (LLN5, LLN10, LLN15, LLN20, and LLN25, respectively).

Relative to an FEV1/FVC equal to or greater than LMS-LLN25 (reference group), the risk for death and the odds of having respiratory symptoms were elevated in participants who had an FEV1/FVC less than LMS-LLN5.

Among these individuals, a significant 68% increased risk of death and 246% increased risk of having respiratory symptoms was observed.

The findings need to be confirmed in other studies, as well as in other ethnicities, report Fragoso and colleagues.

The researchers note the current thresholds for the FEV1/FVC ratio to establish COPD are uncertain, with different organizations using different criteria. Many of these approaches are flawed, they add.

Establishing COPD based solely on FEV1/FVC ratio of 0.70, for example, doesn't account for age-related changes in airflow limitation, they say.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010