PURPOSE: Forced expiratory volume in six seconds (FEV6) is an acceptable alternative to forced vital capacity (FVC) for diagnosing airways obstruction in adults. The acceptability criteria for forced vital capacity (FVC) maneuver during pulmonary function tests is that duration of exhalation should be at least 6 seconds, during which a minimum 1 second plateau could be reached. This total duration may be as long as 15-20 seconds in cases with airways obstruction. The use of FEV6 simplifies testing procedures, reduces test variability, and may improve accuracy in diagnosing airway obstruction.
METHODS: A one year validation study which determined the relationship between FEV1/FEV6 versus FEV1/FVC in the spirometric diagnosis of airway obstruction among Asians. Baseline demographic data, smoking history and spirometric results among 597 Asians were evaluated. The highest postbronchodilator FEV1, FVC, FEV6 and FEV1/FEV6% from tests of acceptable quality were used. Each subject was categorized as having “airway obstruction” by comparing both FEV1/FEV6 with FEV1/FVC with the respective lower limits of normal. FEV1/FVC was used as “gold standard” for diagnosing airways obstruction. Severity of airway obstruction was graded into one of four categories; possible normal variant (FEV1 >100% predicted), mild (FEV1 70-100% predicted), moderate (FEV1 50-70% predicted), severe (FEV1 <50% predcited).
RESULTS: FEV1/FEV6 has 97.6% sensitivity and has 83.6% specificity in diagnosing spirometric mild airway obstruction, with a positive and negative predictive values of 93.1% and 93.3% respectively. A kappa value of .837, a very good overall performance was obtained for FEV1/FEV6% in diagnosing mild airway obstruction. In aaddition, a kappa value of 0.694 was a substantial agreement for FEV1/FEV6 in diagnosing moderate airway obstruction among Asians.
CONCLUSION: FEV6 is an acceptable surrogate for FVC in the diagnosis of a mild to moderate spirometric obstructive patterns among Asians.
CLINICAL IMPLICATIONS: Using FEV6 as a surrogate for FVC has practical advantage because it makes spirometry less demanding because patients would never have to be pushed to a 15 to 20 sec inhalation which may be especially important in older and impaired patients.
DISCLOSURE: Evelyn Pingul, No Financial Disclosure Information; No Product/Research Disclosure Information