Table 6. Summary of PPV and NPV for two-stratum and four-stratum test.

Dataset	Two-stratum test			Four-stratum test
	Positive PPV	Negative NPV		High positive PPV	Positive PPV	Negative NPV	Low negative NPV
Set A	10.9% (1 in 9)	1.8% (1 in 57)		27.4% (1 in 4)	5.5% (1 in 18)	2.0% (1 in 49)	1.0% (1 in 105)
Set B	7.6% (1 in 13)	2.1% (1 in 47)		11.3% (1 in 9)	5.4% (1 in 19)	2.3% (1 in 43)	1.5% (1 in 65)
Set C	10.3% (1 in 10)	1.9% (1 in 53)		22.6% (1 in 4)	6.3% (1 in 16)	2.1% (1 in 47)	1.5% (1 in 67)
Combined	9.4% (1 in 11)	2.0% (1 in 51)		19.3% (1 in 5)	5.4% (1 in 18)	2.3% (1 in 43)	1.1% (1 in 90)

PPV, positive predictive value; NPV, negative predictive value, in its reciprocal form, i.e., 1-NPV. Based on a population lung cancer prevalence of 2.7%.