Table 1.

Selected characteristic of the study population

Characteristics	Cases		Controls		P-value†
	N=742	%	N=742	%
Age at serum sample collection (yr)					0.99
17–19	124	16.71	121	16.31
20–29	348	46.90	352	47.44
30–39	220	29.65	221	29.78
40–51	50	6.74	48	6.47
Mean ± SD	26.25 ± 7.39		26.25 ± 7.34
Age at PTC diagnosis (yr) ¶					0.92
20–29	210	28.30	203	27.36
30–39	310	41.78	323	43.53
40–49	185	24.93	179	24.12
50–62	37	4.99	37	4.99
Mean ± SD	35.14 ± 8.11		35.14 ± 8.05
Sex					>0.99
Female	341	45.96	341	45.96
Male	401	54.04	401	54.04
Race/ethnicity					>0.99
White	468	63.07	467	62.94
Black	131	17.65	132	17.79
Hispanic	68	9.16	68	9.16
Other	55	7.41	55	7.41
Unknown	20	2.70	20	2.70
BMI (kg/m2)					0.19
16–25	261	35.18	286	38.54
25–29.9	143	19.27	128	17.25
30–34.8	16	2.16	10	1.35
missing	322	43.40	318	42.86
Mean ± SD	24.02 ± 3.17		23.77 ± 3.06		0.24
BMI with imputation (kg/m2) ☨					0.07
14–25	452	61.00	494	66.58
25–29.9	260	35.09	227	30.59
30–34.8	29	3.91	21	2.83
Mean ± SD	24.14 ± 3.17		23.79 ± 3.16		0.03
Service					<0.0001
Army	299	40.30	253	34.10
Air Force	193	26.10	150	20.20
Navy	186	25.00	248	33.30
Marines & Coast Guard, combined	64	8.60	91	12.30
Years from serum sample collection to diagnosis (yr)
3–5	115	15.50
6–9	267	35.98
10–13	360	48.52
Mean ± SD	8.89 ± 2.67
Tumor size (mm)
≤10	235	31.67
>10	463	62.40
Missing	44	5.93
Histological type
Classical PTC	600	80.86
Follicular variant of PTC	142	19.14

Abbreviation: BMI, body mass index; PTC, papillary thyroid cancer.

^¶For controls, the age was at the diagnosed year of matched cases

^†Estimated by Chi-squared test for categorical variable and one-way ANOVA for continuous variables

^☨Missing values calculated by multiple imputation