Appendix Table B.

Comparison of Training Data and Validation Data Clusters in the 4-Cluster Model

	Validation		Training		Validation		Training		Validation		Training		Validation		Training
	2nd Line Pharm		2nd Line Pharm		Non-Pharm and 1st Line Pharm		Non-Pharm and 1st Line Pharm		Imaging		Imaging		Specialty		Specialty
	n = 1470		n = 1747		n = 1810		n = 1789		n = 525		n = 305		n = 268		n = 232
Female n, %	818	56%	985	56%	1063	59%	1032	58%	323	62%	196	64%	137	51%	125	54%
Age mean, std	50	16	51	16	48	17	49	17	56	18	55	20	53	16	54	16
Body Mass Index, mean		32		32		32		32		30		30		32		32
Site
BMC	50	3%	56	3%	332	18%	293	16%	12	2%	15	5%	36	113%	23	109%
IMH	406	28%	472	27%	347	19%	335	19%	81	15%	50	16%	53	20%	46	20%
JHU	162	11%	171	10%	395	22%	411	23%	62	12%	38	12%	56	21%	52	22%
UPMC	852	58%	1048	60%	736	41%	750	42%	370	70%	202	66%	124	47%	112	48%
Anxiety or depression n, %	141	10%	143	8%	72	4%	67	4%	30	6%	12	4%	19	7%	20	9%
Obese n, %	775	53%	908	52%	948	52%	967	54%	222	42%	118	39%	139	52%	133	57%
Insurance
SelfPay/Other/Missing	263	18%	289	17%	442	24%	408	23%	90	17%	37	12%	61	23%	48	21%
Medicaid	132	9%	141	8%	188	10%	186	10%	37	7%	21	7%	24	9%	18	8%
Medicare	291	20%	326	19%	295	16%	274	15%	170	32%	93	31%	58	22%	61	26%
private	784	53%	991	57%	885	49%	921	51%	228	43%	153	50%	123	46%	105	45%
Smoking status n,%
Not current smoker	956	65%	1122	64%	1140	63%	1098	61%	391	74%	234	77%	156	59%	140	60%
Current smoker	227	15%	275	16%	179	10%	184	10%	51	10%	22	7%	45	17%	27	12%
Missing/unknown	287	20%	350	20%	491	27%	507	28%	83	16%	48	16%	65	24%	65	28%
Race n,%
White	1289	88%	1556	89%	1250	69%	1264	71%	454	86%	257	85%	210	79%	194	84%
Black	113	8%	116	7%	389	21%	374	21%	45	9%	32	11%	37	14%	25	11%
Missing	32	2%	37	2%	75	4%	81	5%	12	2%	6	2%	8	3%	4	2%
Other	36	2%	38	2%	96	5%	70	4%	14	3%	9	3%	11	4%	9	4%
Hispanic n,%
Non-Hispanic	1397	95%	1652	95%	1658	92%	1612	90%	499	95%	284	93%	242	91%	214	92%
Hispanic	43	3%	44	3%	102	6%	102	6%	15	3%	9	3%	15	6%	10	4%
Missing	30	2%	51	3%	50	3%	75	4%	11	2%	11	4%	9	3%	8	3%
Back pain diagnosis n,%
Axial back pain	999	68%	1118	64%	1472	81%	1452	81%	356	68%	225	74%	156	59%	123	53%
Back and leg	471	32%	629	36%	338	19%	337	19%	169	32%	79	26%	110	41%	109	47%
Duration of LBP n,%
Less than 1 month	996	68%	1188	68%	1147	63%	1115	62%	280	53%	143	47%	117	44%	113	49%
1 to 3 months	282	19%	365	21%	424	23%	441	25%	157	30%	101	33%	89	33%	77	33%
More than 3 months	192	13%	194	11%	239	13%	233	13%	88	17%	60	20%	60	23%	42	18%
STarT Back Category
High	424	29%	482	28%	441	24%	388	22%	141	27%	44	14%	102	38%	94	41%
Low	359	24%	441	25%	686	38%	702	39%	188	36%	141	46%	59	22%	50	22%
Medium	687	47%	824	47%	683	38%	699	39%	196	37%	119	39%	105	39%	88	38%
Chronic at 6 months n,%	328/888	37%	343/1034	33%	267/966	28%	240/893	27%	110/295	37%	42/170	25%	87/151	58%	53/120	44%
ODI Baseline n, mean	1426	40	1698	38	1749	31	1737	31	515	31	298	25	260	40	229	39
ODI 6 Months n, mean	891	22	1034	22	973	19	899	18	298	22	172	17	151	29	121	25

	CLUSTER
	Validation		Training		Validation		Training		Validation		Training		Validation		Training
	2nd Line Pharm		2nd Line Pharm		Non-Pharm and 1st Line Pharm		Non-Pharm and 1st Line Pharm		Imaging		Imaging		Specialty		Specialty
	n = 1470		n = 1747		n = 1810		n = 1789		n = 525		n = 305		n = 268		n = 232
Non-Pharm	494	34%	591	34%	962	53%	901	50%	209	40%	117	38%	42	16%	40	17%
Pharm1	889	60%	948	54%	1430	79%	1438	80%	0	0%	0	0%	116	43%	85	37%
Pharm2	1470	100%	1747	100%	0	0%	12	1%	206	39%	0	0%	154	57%	141	61%
Specialty	0	0%	0	0%	39	2%	69	4%	14	3%	7	2%	268	100%	232	100%
Imaging	255	17%	460	26%	264	15%	266	15%	525	100%	305	100%	88	33%	75	32%

Abbreviations: BMC, Boston medical center; IMH, Institute of mental health; UPMC, University of Pittsburgh medical center; JHU, Johns Hopkins university.