Table 4.

Case–control analysis of serum PFOS and PFNA concentration (dichotomized using median among controls as the cut point) and testicular germ cell tumors, overall and stratified by selected factors, among active-duty U.S. Air Force servicemen (530 cases, 530 controls).

	First/only samplea					Second sample
		PFOS		PFNA			PFOS		PFNA
Stratum	${\mathrm{N}}_{\mathrm{Ca}}{/\mathrm{N}}_{\text{Con}}$	${\text{OR}}_1$b (95% CI)	${\text{OR}}_2$c (95% CI)	${\text{OR}}_1$a (95% CI)	${\text{OR}}_2$b (95% CI)	${\mathrm{N}}_{\mathrm{Ca}}{/\mathrm{N}}_{\text{Con}}$	${\text{OR}}_1$b (95% CI)	${\text{OR}}_2$c (95% CI)	${\text{OR}}_1$b (95% CI)	${\text{OR}}_2$c (95% CI)
Overall	530/530	1.3 (0.9, 1.8)	1.5 (1.05, 2.2)	0.7 (0.5, 0.9)	0.7 (0.5, 0.9)	187/187	2.0 (1.1, 3.7)	2.3 (1.2, 4.3)	0.7 (0.4, 1.2)	0.6 (0.4, 1.2)
By race and ethnicity
Non-Hispanic White	422/422	1.4 (1.0, 2.0)	1.7 (1.1, 2.7)	0.7 (0.5, 0.9)	0.7 (0.4, 1.0)	146/146	2.7 (1.3, 5.2)	3.3 (1.6, 7.0)	0.8 (0.4, 1.5)	0.7 (0.3, 1.4)
Other	108/108	1.0 (0.5, 2.2)	1.1 (0.5, 2.5)	0.6 (0.3, 1.2)	0.6 (0.2, 1.4)	41/41	0.5 (0.1, 2.6)	0.3 ($<0.1$, 2.3)	0.5 (0.1, 1.5)	0.4 (0.1, 1.8)
—	—	$p_{\text{int}}=0.46$ d	$p_{\text{int}}=0.31$	$p_{\text{int}}=0.89$	$p_{\text{int}}=0.94$	—	$p_{\text{int}}=0.06$	$p_{\text{int}}=0.04$	$p_{\text{int}}=0.49$	$p_{\text{int}}=0.57$
By year of sample collection
$\le 2003$	368/368	1.2 (0.8, 1.8)	1.4 (0.9, 2.1)	0.8 (0.6, 1.2)	0.8 (0.6, 1.2)	73/73	1.6 (0.5, 5.1)	2.9 (0.7, 12.3)	0.4 (0.1, 1.2)	0.3 (0.1, 1.0)
$>2003$	162/162	2.4 (0.9, 6.0)	3.8 (1.2, 12.0)	0.4 (0.2, 0.7)	0.4 (0.2, 0.8)	114/114	2.6 (1.2, 5.6)	2.5 (1.1, 5.5)	0.9 (0.5, 1.6)	0.9 (0.4, 2.0)
—	—	$p_{\text{int}}=0.32$ c	$p_{\text{int}}=0.28$	$p_{\text{int}}=0.03$	$p_{\text{int}}=0.08$	—	$p_{\text{int}}=0.73$	$p_{\text{int}}=0.91$	$p_{\text{int}}=0.47$	$p_{\text{int}}=0.23$
By years of service at sample collection
$<1$	316/316	1.2 (0.8, 1.9)	1.4 (0.8, 2.4)	0.5 (0.3, 0.8)	0.4 (0.3, 0.7)	16/13	0.7 (0.1, 5.0)	1.2 (0.1, 12.9)	—	—
1–4	84/88	1.3 (0.5, 3.2)	1.8 (0.6, 5.5)	0.6 (0.3, 1.5)	0.5 (0.2, 1.3)	67/70	4.0 (1.4, 11.6)	5.5 (1.4, 21.5)	0.8 (0.3, 2.0)	0.4 (0.1, 1.3)
$\ge 5$	130/126	2.2 (1.0, 5.0)	3.0 (1.2, 7.7)	1.3 (0.7, 2.5)	1.7 (0.8, 3.4)	104/104	1.9 (0.8, 4.5)	2.0 (0.8, 5.1)	0.8 (0.4, 1.6)	0.8 (0.4, 1.7)
—	—	$p_{\text{int}}=0.35$ c	$p_{\text{int}}=0.56$	$p_{\text{int}}=0.03$	$p_{\text{int}}=0.02$		$p_{\text{int}}=0.18$	$p_{\text{int}}=0.14$	$p_{\text{int}}=0.94$	$p_{\text{int}}=0.94$
By years from sample collection to cancer diagnosis
$<5$	258/258	1.3 (0.7, 2.2)	1.5 (0.8, 2.8)	0.5 (0.4, 0.8)	0.5 (0.3, 0.7)	1/1	—	—	—	—
$\ge 5$	272/272	1.3 (0.8, 2.0)	1.4 (0.9, 2.3)	1.3 (0.7, 2.4)	1.6 (0.8, 3.2)	186/186	2.0 (1.1, 3.7)	2.3 (1.2, 4.3)	0.7 (0.4, 1.2)	0.6 (0.3, 1.1)
—	—	$p_{\text{int}}=0.96$ c	$p_{\text{int}}=0.91$	$p_{\text{int}}=0.02$	$p_{\text{int}}=0.01$	—	—	—	—	—
By tumor histology
Seminoma	300/300	1.3 (0.8, 1.9)	1.8 (1.0, 3.3)	0.9 (0.6, 1.3)	0.9 (0.6, 1.4)	125/125	2.2 (1.1, 4.6)	2.8 (1.2, 6.3)	0.7 (0.4, 1.4)	0.7 (0.3, 1.4)
Nonseminoma	230/230	1.4 (0.8, 2.5)	1.5 (0.9, 2.4)	0.4 (0.2, 0.7)	0.4 (0.2, 0.7)	62/62	2.0 (0.6, 6.0)	2.3 (0.7, 8.1)	0.6 (0.2, 1.6)	0.5 (0.2, 1.8)
—	—	$p_{\text{int}}=0.82$ d	$p_{\text{int}}=0.75$	$p_{\text{int}}=0.02$	$p_{\text{int}}=0.03$		$p_{\text{int}}=0.65$	$p_{\text{int}}=0.57$	$p_{\text{int}}=0.69$	$p_{\text{int}}=0.59$

Note: Median cut points: PFOS, $29.3\text{\hspace{0.17em}ng}/\mathrm{mL}$ for first/only sample and $21.2\text{\hspace{0.17em}ng}/\mathrm{mL}$ for second sample; PFNA, $0.9\text{\hspace{0.17em}ng}/\mathrm{mL}$ for first/only sample and $1.0\text{\hspace{0.17em}ng}/\mathrm{mL}$ for second sample. —, no data; CI, confidence interval; OR, odds ratio; PFAS, per- and polyfluoroalkyl substances; PFNA, perfluorononanoic acid; PFOS, perfluorooctanesulfonic acid.

^a Analysis includes all subjects.

^b ORs and tests of interaction computed by conditional logistic regression of matched pairs with adjustment for military grade and number of deployments.

^c ORs and tests of interaction computed by conditional logistic regression of matched pairs with adjustment for military grade, number of deployments, and all other PFAS (all PFAS covariates involve the same exposure metric and categorization as the PFAS of interest).

^d In general, the $p$-value reflects a test of interaction between PFAS exposure and the stratified variable. For the two cancer-related variables (years from sample collection to cancer diagnosis and tumor histology), the $p$-value reflects a test of heterogeneity between sets of matched case–control pairs defined by the case variable of interest.