PFT Predictive Equations

Predictive equations for Pulmonary Function Testing (PFT) have been developed by several researchers.

The Cotton Standard (CFR 1910.1043) uses predictive equations developed by Knudson. Both an original (1976) and a revised (1983) version of the Knudson equations are included in SYSTOC. A third set of equations comes from Morris, and another comes from Hankinson (NHANES III). Knudson’s predictive values for forced expiratory flow have been questioned, and for that reason, SYSTOC omits them. Morris’ forced expiratory flow equations are considered more accurate. For patients who are Caucasian, Mexican-American, or African-American, you may elect to use the Hankinson formula.

Typically you will set the default method of calculation in Utility > Program Preferences > PFT Defaults prior to performing PFT tests. For more information see Program Preferences.

Calculation Type Description
Morris Uses the Morris equations, and interpretations are based on the FVC, FEV1 and FEF 25%-75%.
Knudson (1976) Follows the Cotton Standard, uses the Knudson equations. Interpretations are based on the FVC and FEV1.
Knudson (1983) 1983 revision of original 1976 equations.
Hankinson (NHANES III) Uses formula derived by Hankinson, Odencrantz and Fedan from NHANES III survey. Valid only for three race/ethnic groups—Caucasian, African-American, and Mexican-American.