Table 4.

Effect of change of reference standard to NHANES III (Hankinson et al 1999) on the classification of severity of obstructive spirometric ‘abnormality’ (n = 234), using percent predicted FEV₁

Reference equation	Percent disagreement	Weighted Kappa *	Generalized McNemar’s test	Comment on comparison with NHANES III reference standard
Morris et al 1971	28.20	0.77 (0.72, 0.82)	p < 0.001	Morris classifies a lower level of severity
Kory et al 1961	17.94	0.85 (0.81, 0.90)	p < 0.001	Kory classifies a lower level of severity
Crapo et al 1981	11.96	0.91 (0.88, 0.94)	p = 0.77	Crapo classifies a similar level of severity
Knudson et al 1976	18.80	0.85 (0.80, 0.89)	p < 0.001	Knudson usually classifies a lower level of severity
Knudson et al 1983	14.53	0.88 (0.85, 0.92)	p = 0.06	Knudson tends to classify a lower level of severity, although the trend is not statistically significant

^*Numbers in parenthesis reflect 95% confidence intervals