Variable	UMC (n=375)	UMC+CC (n=375)

Age, years, mean (SD)	30.8 (8.8)	30.9 (8.7)


Sex, n (%)
Male	287 (76.5)	288 (76.8)

Female	88 (23.5)	87 (23.2)


Race, n (%)
White	252 (67.2)	255 (68.0)

Black or African American	72 (19.2)	77 (20.5)

Asian	20 (5.3)	10 (2.7)

Native Hawaiian or Other Pacific Islander	2 (0.5)	7 (1.9)

American Indian or Alaska Native	2 (0.5)	0 (0)

Multiracial	8 (2.1)	6 (1.6)

Unspecified	19 (5.1)	20 (5.3)


Ethnicity, n (%)
Not Hispanic or Latino	286 (76.3)	300 (80.0)

Hispanic or Latino	66 (17.6)	52 (13.9)

Unspecified	23 (6.1)	23 (6.1)


Current LBP episode duration, n (%)
7 days	81 (21.6)	73 (19.5)

7 days to <16 days	40 (10.7)	33 (8.8)

16 days to <1 month	23 (6.1)	37 (9.9)

1–3 months	40 (10.7)	39 (10.4)

> 3 months to <6 months	23 (6.1)	25 (6.7)

6 months to <1 year	28 (7.5)	27 (7.2)

1 year or more	140 (37.3)	141 (37.6)


PROMIS Pain intensity, 0–10, mean (SD)	5.0 (1.9)	5.0 (1.9)

PROMIS Pain interference, T-score, mean (SD)<.BIG>	58.9 (7.2)	60.0 (7.1)

PROMIS Physical function, T-score, mean (SD)^*	56.8 (7.1)	56.8 (7.3)

PROMIS Sleep disturbance, T-score, mean (SD)	55.5 (7.6)	55.0 (7.8)

PROMIS Fatigue, T-score, mean (SD)	51.5 (9.8)	51.8 (10.2)

PROMIS Anxiety, T-score, mean (SD)	48.1 (9.0)	48.7 (8.7)

PROMIS Depression, T-score, mean (SD)	45.0 (6.9)	45.8 (7.1)

PROMIS Social Role, T-score, mean (SD)^*	54.6 (9.1)	55.1 (8.9)

^* Transformed (100-T-score) to make a higher score indicative of worse health; .
Outcomes Measurement Information System
UMC = usual medical care;
UMC+CC = usual medical care plus chiropractic care

Table 1. Baseline characteristics of participants allocated to usual medical care plus chiropractic care versus usual medical care alone (n=750).