World J Oncol

World Journal of Oncology, ISSN 1920-4531 print, 1920-454X online, Open Access

Article copyright, the authors; Journal compilation copyright, World J Oncol and Elmer Press Inc

Journal website http://www.wjon.org

Original Article

Volume 2, Number 3, June 2011, pages 123-132

Analysis of Pain and Interference Patterns With Brief Pain Inventory in Patients With Bone Metastases: A Confirmatory Study

**Table 1.** Baseline Demographic Information on Study Patients and Excluded Patients
	Study Patients (n = 336)	Excluded Patients (n = 49)	P-value
Age (year)			0.0131
N	336	49
Mean ± SD	65.3 ± 12.0	69.6 ± 12.7
Inter-quartiles	57 - 74	61 - 79
Median (range)	67 (30 - 91)	71 (33 - 90)
KPS			< 0.0001
N	323	49
Mean ± SD	71.3 ± 13.4	63.3 ± 11.1
Inter-quartiles	60 - 80	60 - 70
Median (range)	70 (30 - 90)	60 (30 - 90)
Worst pain			0.9859
N	336	48
Mean ± SD	7.38 ± 2.34	7.48 ± 2.05
Inter-quartiles	6 - 10	6 - 9
Median (range)	8.0 (2 - 10)	8.0 (3 - 10)
Average pain			0.7995
N	336	42
Mean ± SD	4.98 ± 2.30	5.10 ± 2.15
Inter-quartiles	3 - 7	3 - 7
Median (range)	5.0 (0 - 10)	5.0 (1 - 10)
Current pain			0.3684
N	336	46
Mean ± SD	3.78 ± 2.78	3.33 ± 2.46
Inter-quartiles	2 - 6	2 - 5
Median (range)	3.0 (0 - 10)	3.0 (0 - 10)
Total daily morphine equivalent (mg)		0.1555
N	333	49
Mean ± SD	95.5 ± 216.5	137.8 ± 232.5
Inter-quartiles	0 - 100	0 - 150
Median (range)	20 (0 - 2600)	40 (0 - 1056)
Gender			0.0303
Male	192 (57.1%)	36 (73.5%)
Female	144 (42.9%)	13 (26.5%)
Dose/Fraction			0.8437
8 Gy/1	209 (62.2%)	31 (63.3%)
20 Gy/5	111 (33.0%)	15 (30.4%)
30 Gy/10	7 (2.1%)	1 (2.0%)
Others	9 (2.7%)	2 (4.1%)
Primary cancer site			0.3132
Breast	90 (26.8%)	9 (18.4%)
Prostate	82 (24.4%)	16 (32.6%)
Lung	85 (25.3%)	9 (18.4%)
Bladder	13 (3.9%)	1 (2.0%)
Pancreas/Gastric	10 (3.0%)	3 (6.1%)
Others	56 (16.7%)	11 (22.4%)
Pain site			0.6352
Lower limb	152 (45.2%)	20 (40.8%)
Spine	112 (33.3%)	17 (34.7%)
Upper limb	42 (12.5%)	6 (12.2%)
Other - ribs	22 (6.6%)	3 (6.1%)
Other - chest wall	8 (2.4%)	3 (6.1%)

Table 1. Baseline Demographic Information on Study Patients and Excluded Patients

Study Patients (n = 336)

Excluded Patients (n = 49)

P-value

Age (year)

0.0131

336

Mean ± SD

65.3 ± 12.0

69.6 ± 12.7

Inter-quartiles

57 - 74

61 - 79

Median (range)

67 (30 - 91)

71 (33 - 90)

KPS

< 0.0001

323

Mean ± SD

71.3 ± 13.4

63.3 ± 11.1

Inter-quartiles

60 - 80

60 - 70

Median (range)

70 (30 - 90)

60 (30 - 90)

Worst pain

0.9859

336

Mean ± SD

7.38 ± 2.34

7.48 ± 2.05

Inter-quartiles

6 - 10

6 - 9

Median (range)

8.0 (2 - 10)

8.0 (3 - 10)

Average pain

0.7995

336

Mean ± SD

4.98 ± 2.30

5.10 ± 2.15

Inter-quartiles

3 - 7

Median (range)

5.0 (0 - 10)

5.0 (1 - 10)

Current pain

0.3684

336

Mean ± SD

3.78 ± 2.78

3.33 ± 2.46

Inter-quartiles

2 - 6

2 - 5

Median (range)

3.0 (0 - 10)

Total daily morphine equivalent (mg)

0.1555

333

Mean ± SD

95.5 ± 216.5

137.8 ± 232.5

Inter-quartiles

0 - 100

0 - 150

Median (range)

20 (0 - 2600)

40 (0 - 1056)

Gender

0.0303

Male

192 (57.1%)

36 (73.5%)

Female

144 (42.9%)

13 (26.5%)

Dose/Fraction

0.8437

8 Gy/1

209 (62.2%)

31 (63.3%)

20 Gy/5

111 (33.0%)

15 (30.4%)

30 Gy/10

7 (2.1%)

1 (2.0%)

Others

9 (2.7%)

2 (4.1%)

Primary cancer site

0.3132

Breast

90 (26.8%)

9 (18.4%)

Prostate

82 (24.4%)

16 (32.6%)

Lung

85 (25.3%)

9 (18.4%)

Bladder

13 (3.9%)

1 (2.0%)

Pancreas/Gastric

10 (3.0%)

3 (6.1%)

Others

56 (16.7%)

11 (22.4%)

Pain site

0.6352

Lower limb

152 (45.2%)

20 (40.8%)

Spine

112 (33.3%)

17 (34.7%)

Upper limb

42 (12.5%)

6 (12.2%)

Other - ribs

22 (6.6%)

3 (6.1%)

Other - chest wall

8 (2.4%)

3 (6.1%)

**Table 2.** Summary of BPI Scores by Item and Internal Consistency Among Subscales in Study Patients (N = 336)
BPI Items	Item Statistics	Standardized Cronbach’s alpha
↑ Removing the sleep item caused alpha to increase in both two and three subscale analysis, meaning it correlated poorly with the other BPI items.
			Pain Subscale (alpha = 0.76)	Pain Subscale (alpha = 0.76)
Worst pain	7.4	2.3	0.57	0.71	0.57	0.71
Average pain	5.0	2.3	0.68	0.59	0.68	0.59
Current pain	3.8	2.8	0.54	0.75	0.54	0.75
			Interference Subscale (alpha = 0.87)	Activity Subscale (alpha = 0.81)
General activity	6.5	3.2	0.77	0.83	0.74	0.70
Walking ability	5.8	3.6	0.59	0.86	0.60	0.78
Normal work	6.8	3.5	0.71	0.84	0.71	0.72
Sleep	4.8	3.4	0.52	0.87↑	0.47	0.83↑
					Affect Subscale (alpha = 0.77)
Mood	5.1	3.4	0.66	0.85	0.65	0.63
Enjoyment of life	6.5	3.3	0.73	0.84	0.56	0.73
Relations	3.4	3.5	0.53	0.87	0.59	0.70

Table 2. Summary of BPI Scores by Item and Internal Consistency Among Subscales in Study Patients (N = 336)

BPI Items

Item Statistics

Standardized Cronbach’s alpha

Two Subscales

Three Subscales

Mean

Correlation With Total

Alpha With Item Deleted

Correlation With Total

Alpha With Item Deleted

↑ Removing the sleep item caused alpha to increase in both two and three subscale analysis, meaning it correlated poorly with the other BPI items.

Pain Subscale (alpha = 0.76)

Worst pain

7.4

2.3

0.57

0.71

0.57

0.71

Average pain

5.0

2.3

0.68

0.59

0.68

0.59

Current pain

3.8

2.8

0.54

0.75

0.54

0.75

Interference Subscale (alpha = 0.87)

Activity Subscale (alpha = 0.81)

General activity

6.5

3.2

0.77

0.83

0.74

0.70

Walking ability

5.8

3.6

0.59

0.86

0.60

0.78

Normal work

6.8

3.5

0.71

0.84

0.71

0.72

Sleep

4.8

3.4

0.52

0.87↑

0.47

0.83↑

Affect Subscale (alpha = 0.77)

Mood

5.1

3.4

0.66

0.85

0.65

0.63

Enjoyment of life

6.5

3.3

0.73

0.84

0.56

0.73

Relations

3.4

3.5

0.53

0.87

0.59

0.70

**Table 3.** Comparison of Model Fit of Different Structural Models
Model	Modification	Goodness of Fit Index (Adjusted)	Chi-Square (df)	RMSEA (Upper CL)	Comparative Fit Index	Non-Normed Fit Index
df = degrees of freedom; CL = confidence limit
1 factor: 10 items	None (no structure)	0.88	210.7 (34)	0.12 (0.14)	0.88	0.84
2 factors: Pain and Interference	None (default structure)	0.93	126.3 (32)	0.09 (0.11)	0.94	0.91
2 factors: Pain and Interference	Covary error terms of average pain–current pain, mood–relations, mood–enjoyment, relations–enjoyment	0.97	46.1 (28)	0.04 (0.07)	0.99	0.98
2 factors: Pain and Interference	Drop Sleep; Covary error terms of average pain–current pain, mood–relations, mood–enjoyment, relations–enjoyment	0.98	29.7 (20)	0.04 (0.07)	0.99	0.99
3 factors: Pain, Activity and Affect	None (load sleep on activity)	0.94	111.3 (29)	0.09 (0.11)	0.95	0.91
3 factors: Pain, Activity and Affect	Covary error terms of average pain–current pain, mood–relations	0.97	46.0 (27)	0.05 (0.07)	0.99	0.98
3 factors: Pain, Activity and Affect	Drop Sleep; Covary error terms of average pain–current pain, mood–relations	0.98	28.2 (19)	0.04 (0.07)	0.99	0.99
Acceptable model fit		Perfect fit = 1	Smaller value	RMSEA < 0.10	> 0.90	> 0.90

Table 3. Comparison of Model Fit of Different Structural Models

Model

Modification

Goodness of Fit Index (Adjusted)

Chi-Square (df)

RMSEA (Upper CL)

Comparative Fit Index

Non-Normed Fit Index

df = degrees of freedom; CL = confidence limit

1 factor: 10 items

None (no structure)

0.88

210.7 (34)

0.12 (0.14)

0.88

0.84

2 factors: Pain and Interference

None (default structure)

0.93

126.3 (32)

0.09 (0.11)

0.94

0.91

2 factors: Pain and Interference

Covary error terms of average pain–current pain, mood–relations, mood–enjoyment, relations–enjoyment

0.97

46.1 (28)

0.04 (0.07)

0.99

0.98

2 factors: Pain and Interference

Drop Sleep; Covary error terms of average pain–current pain, mood–relations, mood–enjoyment, relations–enjoyment

0.98

29.7 (20)

0.04 (0.07)

0.99

3 factors: Pain, Activity and Affect

None (load sleep on activity)

0.94

111.3 (29)

0.09 (0.11)

0.95

0.91

3 factors: Pain, Activity and Affect

Covary error terms of average pain–current pain, mood–relations

0.97

46.0 (27)

0.05 (0.07)

0.99

0.98

3 factors: Pain, Activity and Affect

Drop Sleep; Covary error terms of average pain–current pain, mood–relations

0.98

28.2 (19)

0.04 (0.07)

0.99

Acceptable model fit

Perfect fit = 1

Smaller value

RMSEA < 0.10

> 0.90

**Table 4.** CFA With Sleep Interference Excluded Demonstrating Comparable Factor Loadings and Reliability of Both Two- and Three-Factor Models
BPI Items	Two Subscales	Three Subscales
	Composite Reliability Pain Factor 0.72	Composite Reliability Pain Factor 0.70
Worst pain	0.73	0.72	21.1	0.72	0.73	21.0
Average pain	0.76	0.49	16.5	0.74	0.48	16.2
Current pain	0.53	0.24	9.8	0.50	0.24	9.7
	Composite Reliability Interference Factor 0.83	Composite Reliability Activity Factor 0.77
General activity	0.82	0.77	27.6	0.83	0.78	25.9
Walking ability	0.63	0.47	16.6	0.63	0.47	16.3
Normal work	0.71	0.61	21.3	0.72	0.62	20.5
				Composite Reliability Affect Factor 0.70
Mood	0.62	0.37	14.0	0.66	0.42	16.9
Enjoyment of life	0.75	0.63	22.6	0.77	0.72	25.3
Relations	0.50	0.22	9.6	0.56	0.27	11.7
	Correlation Pain-Interference: 0.77	Correlation Pain-Activity: 0.75
		Correlation Pain-Affect: 0.76
		Correlation Activity-Affect: 0.92

Table 4. CFA With Sleep Interference Excluded Demonstrating Comparable Factor Loadings and Reliability of Both Two- and Three-Factor Models

BPI Items

Two Subscales

Three Subscales

Factor Loading

R-Squared

t-statistic

Factor Loading

R-Squared

t-statistic

Composite Reliability Pain Factor 0.72

Composite Reliability Pain Factor 0.70

Worst pain

0.73

0.72

21.1

0.72

0.73

21.0

Average pain

0.76

0.49

16.5

0.74

0.48

16.2

Current pain

0.53

0.24

9.8

0.50

0.24

9.7

Composite Reliability Interference Factor 0.83

Composite Reliability Activity Factor 0.77

General activity

0.82

0.77

27.6

0.83

0.78

25.9

Walking ability

0.63

0.47

16.6

0.63

0.47

16.3

Normal work

0.71

0.61

21.3

0.72

0.62

20.5

Composite Reliability Affect Factor 0.70

Mood

0.62

0.37

14.0

0.66

0.42

16.9

Enjoyment of life

0.75

0.63

22.6

0.77

0.72

25.3

Relations

0.50

0.22

9.6

0.56

0.27

11.7

Correlation Pain-Interference: 0.77

Correlation Pain-Activity: 0.75

Correlation Pain-Affect: 0.76

Correlation Activity-Affect: 0.92

**Table 5.** Summary of Subscale Mean Scores in Patients With Upper vs. Lower Skeletal Pain
Subscales	Upper Skeletal Pain (n = 130)	Lower Skeletal Pain (n = 199)	p-value	Mean Difference (95% CI)
Mean Pain	5.25	1.91	5.47	2.08	0.3461	0.21 (-0.23 - 0.66)
Mean Activity	5.70	2.82	6.85	2.94	0.0005	1.14 (0.50 - 1.79)
Mean Affect	5.05	2.74	4.97	2.83	0.8172	0.07 (-0.55 - 0.69)

Table 5. Summary of Subscale Mean Scores in Patients With Upper vs. Lower Skeletal Pain

Subscales

Upper Skeletal Pain (n = 130)

Lower Skeletal Pain (n = 199)

p-value

Mean Difference (95% CI)

Mean

Mean Pain

5.25

1.91

5.47

2.08

0.3461

0.21 (-0.23 - 0.66)

Mean Activity

5.70

2.82

6.85

2.94

0.0005

1.14 (0.50 - 1.79)

Mean Affect

5.05

2.74

4.97

2.83

0.8172

0.07 (-0.55 - 0.69)

**Table 6.** Mean Activity Scores in Upper and Lower Skeletal Patient Groups Stratified by Pain Subgroups
Pain subgroups	Upper Skeletal Pain (n = 130)	Lower Skeletal Pain (n = 199)	p-value	Mean Difference (95% CI)
Mild (mean Pain ≤ 4)	35	4.03 (2.69)	51	4.14 (3.20)	0.8617	0.12 (-1.20 - 1.43)
Moderate (mean Pain 4 - 7)	69	6.03 (2.74)	101	7.37 (2.28)	0.0007	1.34 (0.57 - 2.10)
Severe (mean Pain ≥ 7)	26	7.08 (2.14)	47	8.65 (1.66)	0.0008	1.58 (0.68 - 2.47)

Table 6. Mean Activity Scores in Upper and Lower Skeletal Patient Groups Stratified by Pain Subgroups

Pain subgroups

Upper Skeletal Pain (n = 130)

Lower Skeletal Pain (n = 199)

p-value

Mean Difference (95% CI)

Mean (SD)

Mild (mean Pain ≤ 4)

4.03 (2.69)

4.14 (3.20)

0.8617

0.12 (-1.20 - 1.43)

Moderate (mean Pain 4 - 7)

6.03 (2.74)

101

7.37 (2.28)

0.0007

1.34 (0.57 - 2.10)

Severe (mean Pain ≥ 7)

7.08 (2.14)

8.65 (1.66)

0.0008

1.58 (0.68 - 2.47)

**Table 7.** Comparison of Wu et al. and Our Results (Three-Factor Analyses)
Three-Factor Test	Wu et al. [11]	Our Results
Cronbach’s Alpha
Initial Activity Alpha	0.79	0.81
Activity Alpha Removing Sleep	0.89	0.83
Result	Increase	Increase
Model Fit
Chi-square with sleep	152.6	46.0
Chi-square without sleep	37.9	28.2
Result	Decrease	Decrease
Model CFA
Correlation pain-activity	0.52	0.75
Correlation pain-affect	0.55	0.76
Correlation activity-affect	0.83	0.92

Table 7. Comparison of Wu et al. and Our Results (Three-Factor Analyses)

Three-Factor Test

Wu et al. [11]

Our Results

Cronbach’s Alpha

Initial Activity Alpha

0.79

0.81

Activity Alpha Removing Sleep

0.89

0.83

Result

Increase

Model Fit

Chi-square with sleep

152.6

46.0

Chi-square without sleep

37.9

28.2

Result

Decrease

Model CFA

Correlation pain-activity

0.52

0.75

Correlation pain-affect

0.55

0.76

Correlation activity-affect

0.83

0.92