Table III.

Adjusted ORs and 95% CIs for assay measures and lung cancer risk in a nested case-control study within the PLCO Cancer Screening Trial

Assay type by quartile	Number of controls	Number of casesa	ORb	95% CI		P for trendc
						Score	Continuous
Comet tail DNA (%)
3.6–6.1	29	21	1.00	Referent
6.2–7.1	30	32	1.49	0.69	3.21
7.2–8.4	29	36	1.71	0.81	3.63
8.5–17.4	29	25	1.20	0.54	2.65	0.60	0.92
Comet tail length (μm)
15.0–29.4	29	27	1.00	Referent
29.5–33.2	29	28	1.01	0.47	2.18
33.3–36.0	30	25	0.90	0.42	1.91
36.1–45.0	29	34	1.26	0.60	2.63	0.61	0.75
CDM
15.1–17.4	29	31	1.00	Referent
17.5–18.3	30	29	0.90	0.43	1.89
18.4–19.5	29	28	0.90	0.43	1.88
19.6–27.8	29	26	0.85	0.40	1.77	0.67	0.80
OTM
0.8–1.2	29	23	1.00	Referent
1.3–1.5	30	36	1.57	0.74	3.30
1.6–1.7	29	24	1.04	0.48	2.26
1.8–4.5	29	31	1.39	0.65	2.97	0.68	0.92
DRC (%)d
12.5–20.2	29	28	1.00	Referent
10.6–12.4	28	31	1.15	0.55	2.41
9.0–10.5	31	31	1.03	0.50	2.16
5.0–8.9	29	27	0.96	0.45	2.04	0.86	0.67
Bleomycin mutagen sensitivity (breaks/cell)
0.08–0.31	31	22	1.00	Referent
0.32–0.45	32	26	1.15	0.54	2.45
0.46–0.57	26	26	1.41	0.65	3.08
0.58–1.26	28	41	2.09	1.00	4.37	0.04	0.05

Assay measures were divided into quartiles based on the control distribution. The alkaline Comet assay was performed on unchallenged cells and measured endogenous levels of DNA damage. The Comet measures of CDM and OTM do not have units. The DRC measure used the HCR assay with the mutagen BPDE and is the percent of repaired plasmids relative to undamaged plasmids. The mutagen sensitivity assay used the mutagen bleomycin and measured the number of chromatid breaks per cell.

^aThe number of cases may not sum to total due to poor growth of a few LCLs in some laboratories.

^bAdjusted for age.

^cP for trends are a 1 df score test and based on the continuous underlying variable.

^dQuartile sequence is reversed because increased DRC relative to lower repair is considered the referent group.