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Table 6 Factors associated with the presence of exclusionary condition among subjects classified as chronic fatigue syndrome (CFS) at clinic evaluation

From: An evaluation of exclusionary medical/psychiatric conditions in the definition of chronic fatigue syndrome

Characteristics

  

Exclusionary condition

Odds ratio (OR)

 

All

Yes

No

Unadjusted ORs

Adjusted ORs

 

n = 210

n = 100 (48%)

n = 110 (52%)

(95% CI) †

(95% CI)

Telephone Classification

        

   CFS-like

169

80.48

85

50.30

84

49.70

1.75 (0.87-3.54)

1.48 (0.61-3.56)

   Unwell

41

19.52

15

36.59

26

63.41

1.00

1.00

Age (years), mean (standard deviation, SD)

45.06

(9.65)

45.99

(8.98)

44.22

(10.19)

1.21 (0.92-1.59)

1.06 (0.74-1.54)

Sex

        

   Male

38

18.10

18

47.37

20

52.63

0.99 (0.49-2.00)

1.65 (0.69-3.92)

   Female

172

81.90

82

47.67

90

52.33

1.00

1.00

Race

        

   Black

35

16.67

14

40.00

21

60.00

0.67 (0.32-1.40)

0.56 (0.20-1.52)

   Other

13

6.19

5

38.46

8

61.54

0.63 (0.20-1.99)

0.62 (0.15-2.51)

   White

162

77.14

81

50.00

81

50.00

1.00

1.00

Residential areas

        

   Rural

106

50.48

54

50.94

52

49.06

2.28 (0.99-5.29)

1.47 (0.51-4.20)

   Urban

72

34.29

36

50.00

36

50.00

2.20 (0.91-5.30)

1.53 (0.55-4.27)

   Metropolitan

32

15.24

10

31.25

22

68.75

1.00

1.00

Body mass index (kg/m2), mean (SD)

28.69

(5.18)

29.50

(5.42)

27.95

(4.87)

1.36 (1.03-1.79)

1.47 (1.05-2.06)

Multidimensional fatigue inventory

      

Per SD increment

Per SD increment

   General fatigue

17.05

(2.36)

17.34

(2.09)

16.79

(2.57)

1.27 (0.96-1.70)

1.22 (0.81-1.84)

   Physical fatigue

14.52

(3.31)

14.88

(3.22)

14.19

(3.38)

1.24 (0.94-1.63)

0.83 (0.52-1.34)

   Reduced Activity

11.96

(4.10)

12.33

(4.19)

11.63

(4.02)

1.19 (0.90-1.56)

0.83 (0.54-1.26)

   Reduced Motivation

12.44

(3.38)

13.05

(3.63)

11.89

(3.05)

1.43 (1.07-1.89)

1.44 (0.94-2.20)

   Mental fatigue

14.05

(3.75)

14.49

(3.72)

13.65

(3.75)

1.25 (0.95-1.65)

1.19 (0.80-1.77)

SF-36

      

Per SD increment

Per SD increment

   Physical functioning

57.37

(24.54)

52.83

(24.01)

61.45

(24.40)

0.70 (0.53-0.92)

0.77 (0.28-2.12)

   Role physical

9.05

(19.45)

5.50

(13.09)

12.27

(23.40)

0.67 (0.48-0.93)

0.63 (0.40-1.00)

   Bodily pain

38.30

(19.86)

35.66

(18.93)

40.70

(20.46)

0.77 (0.58-1.02)

0.60 (0.27-1.31)

   Social functioning

49.82

(24.74)

47.25

(26.03)

52.16

(23.39)

0.82 (0.62-1.08)

1.24 (0.62-2.46)

   Mental health

54.27

(22.15)

52.04

(21.59)

56.29

(22.55)

0.82 (0.63-1.08)

1.38 (0.55-3.46)

   Role emotional

27.46

(37.36)

23.66

(35.23)

30.90

(39.03)

0.82 (0.62-1.08)

0.94 (0.55-1.61)

   Vitality

22.29

(16.21)

21.55

(16.96)

22.95

(15.54)

0.92 (0.70-1.20)

1.20 (0.72-1.99)

   General health

40.17

(19.46)

38.10

(20.87)

42.05

(17.97)

0.81 (0.62-1.07)

0.99 (0.51-1.92)

   PCS*

36.67

(9.92)

35.31

(9.91)

37.91

(9.81)

0.77 (0.58-1.01)

1.47 (0.17-12.75)

   MCS*

36.75

(12.58)

35.75

(12.78)

37.67

(12.39)

0.86 (0.65-1.13)

0.69 (0.12-3.99)

   HUI2*

61.94

(10.80)

59.95

(10.96)

63.76

(10.37)

0.69 (0.52-0.92)

Not included

SI

      

Per SD increment

Per SD increment

   SI_CFS

49.03

(16.60)

50.20

(15.94)

47.97

(17.17)

1.15 (0.87-1.50)

0.68 (0.42-1.11)

   SI_NCFS

36.98

(18.68)

39.95

(19.63)

34.24

(17.40)

1.37 (1.03-1.82)

1.47 (0.93-2.32)

  1. Note: adjusted ORs were obtained for the multiple logistic regression models including all variables in the table; p-value < 0.05 were in bold font.
  2. * Nichole's health utility index 2 (HUI2) was included in the multivariate model because it is a linear combination of 8 SF-36 subscales and strongly correlated with Physical Component Summary (PCS) and Mental Component Summary (MCS).
  3. CI: confidence interval; SI_CFS: symptom inventory summary score of 8 CFS symptoms; SI_NCFS: symptom inventory summary score of non-CFS symptoms