TABLE 3.

Projected impact of observed proportional bias on interpretation

Resistance	Measurements		4-year-old male (105 cm)			8.5-year-old male (129 cm)
	Value measured on IOS kPa·L−1·s−1	Projected value measured on tremoFlo# kPa·L−1·s−1	IOS value z-score¶	tremoFlo value z-score¶	Difference z-score+	IOS value z-score¶	tremoFlo value z-score¶	Difference z-score+
R5	0.75	0.73	−1.35	−1.44	0.09	0.20	0.10	0.09
	1	1.01	−0.27	−0.22	−0.05	1.28	1.33	−0.05
	1.25	1.29	0.82	1.01	−0.19	2.37	2.56	−0.19
	1.5	1.58	1.90	2.24	−0.33	3.45	3.79	−0.33
R10	0.75	0.85	−0.71	−0.28	−0.43	0.68	1.11	−0.43
	1	1.19	0.39	1.24	−0.85	1.79	2.64	−0.85
	1.25	1.54	1.50	2.77	−1.27	2.90	4.17	−1.27
	1.5	1.88	2.61	4.30	−1.69	4.00	5.69	−1.69

IOS: MasterScreen impulse oscillometry system. ^#: based on the observed average resistance- and oscillatory frequency-specific proportional bias (note: we conservatively used the bias observed in 38 children, without removing the outlier identified for R₅); ^¶: z-score values calculated using IOS-specific paediatric normative values [9]; ⁺: z-score difference between those derived from the IOS versus tremoFlo, with negative values indicating a lower z-score value on the IOS than the tremoFlo.