Table 1.

Equation coefficients for the OLIN reference values for spirometry

		A	B	B1	B2	B3	B4	B5
FEV1	Women	0.3832	−0.0013797	−6.236984	−0.001575	−0.002130	0.000881	0.097457
	Men	0.5335	−0.0013209	−6.792881	−0.016061	−0.000654	−0.000631	0.092415
FVC	Women	0.4835	−0.0009121	−7.504292	−0.006537	−0.001433	−0.000418	0.101606
	Men	0.6515	−0.0009156	−8.145885	−0.024025	−0.000089	−0.000888	0.100738
SVC	Women	0.4890	−0.0004222	−6.585401	−0.018584	−0.000965	−0.000754	0.096274
	Men	0.6842	−0.0013804	−9.466451	−0.013372	−0.000253	−0.000410	0.105695
VC	Women	0.4728	−0.0004556	−7.174368	−0.016404	−0.001117	−0.000775	0.101837
	Men	0.6852	−0.0014865	−9.237482	−0.012298	−0.000215	−0.000550	0.104602
FEV1/FVC	Women	0.0414	0.0003501	21.774779	−0.121986	0.000235	0.002045	−0.014863
	Men	0.0474	0.0000904	20.349431	−0.034677	−0.000816	0.000313	−0.018407
FEV1/VC	Women	0.0397	0.0004102	21.585726	−0.134590	0.000216	0.002355	−0.012948
	Men	0.0510	0.0000706	19.348156	−0.033104	−0.000538	−0.000496	−0.019745

The standard deviation (SD) is calculated by the following formula: A+B*age.

The reference value (i.e., the mean) is calculated by the following formula: (Σ B(J)*X(J))*SD.

The LLN (lower limit of normal) is calculated by the following formula: Mean-1.645*SD.

FEV1=Volume exhaled in the first second of a forced expiratory manoeuvre.

FVC=Forced expiratory vital capacity.

SVC=Slow expiratory vital capacity.

VC=The highest value of FVC and SVC.

X1=1.

X2=Age (in years).

X3=max(min(age-40, 20), 0)²+40*max(age-60, 0).

X4=max(min(age-60, 20), 0)²+40*max(age-80, 0).

X5=Height (in cm).