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Table 1 Performance Scales-based, IRT-derived, scaled scores of disability by patient characteristics

From: Item response theory-based measure of global disability in multiple sclerosis derived from the Performance Scales and related items

Characteristic

N (%)

Global disability

Residual physical disability

Residual mental disability

  

Bifactor

Unidimensional

Unidimensional

Bifactor

Bifactor

Patterna(95% CI)

Patterna(95% CI)

Summedb(95% CI)

Patterna(95% CI)

Patterna(95% CI)

Age at assessment (y.)

      

≤ 35

749 (19.1)

45.2 (44.1, 46.2)***

44.6 (43.6, 45.7)***

44.5 (43.5, 45.6)***

42.5 (41.7, 43.4)***

41.2 (40.2, 42.2)***

36 – 55

1760 (44.8)

50.3 (49.6, 51.0)

50.1 (49.4, 50.8)

50.0. (49.3, 50.7)

47.8 (47.1, 48.4)

47.4 (46.6, 48.2)

≥ 56

1417 (36.1)

52.2 (51.5, 53.0)

52.7 (52.0, 53.5)

52.9 (52.2, 53.7)

56.7 (55.9, 57.5)

57.9. (57.0, 58.8)

Disease duration (y.)

      

≤ 10

1713 (43.6)

46.2 (45.5, 46.9)***

45.7 (45.0, 46.5)***

45.5 (44.8, 46.2)***

45.2 (44.5, 45.8)***

44.3 (43.6, 45.0)***

11 – 20

1109 (28.3)

51.7 (50.9, 52.6)

51.8 (51.0, 52.7)

51.9 (51.1, 52.7)

50.6 (49.7, 51.5)

50.7 (49.7, 51.7)

≥ 21

1104 (28.1)

54.2 (53.3, 55.0)

54.8 (54.0, 55.6)

55.1 (54.3, 55.9)

56.9 (56.0, 57.8)

58.2 (57.1, 59.2)

Gender

      

Female

3102 (79.4)

49.7 (49.2, 50.2)**

49.6 (49.1, 50.1)***

49.5 (49.0, 50.0)***

48.8 (48.3, 49.3)***

48.5. (47.9, 49.1)***

Male

803 (20.6)

51.3 (50.2 52.4)

51.6 (50.5, 52.7)

51.9 (50.8, 53.0)

54.8 (53.7, 55.9)

55.6 (54.4, 56.9)

Race/Ethnicity

      

White

3491 (90.2)

49.8 (49.3, 50.3)***

49.8 (49.3, 50.3)***

49.7 (49.3, 50.2)***

50.0 (49.5, 50.5)*

50.0 (49.4, 50.6)*

African American

132 (3.4)

50.7 (48.2, 53,2)

51.0 (48.6, 53.4)

51.5 (49.0, 54.0)

51.8 (49.0, 54.5)

52.1 (48.9, 55.3)

Hispanic/Latino

120 (3.1)

48.1. (45.2, 51.0)

47.9 (45.0, 50.8)

47.8 (44.8, 50.5)

46.5 (43.8, 49.2)

45.9. (42.7, 49.1)

Native American

76 (2.0)

56.7 (53.3, 60.1)

56.6 (53.2, 59.9)

56.7 (53.3, 60.1)

48.3 (45.6, 51.1)

48.0 (44.8, 51.3)

Other

49 (1.3)

53.4 (48.5, 58.1)

53.1 (48.3, 57.9)

53.3 (48.4, 58.3)

47.3. (43.6, 51.0)

46.8. (42.4, 51.2)

Disease modifying therapy

      

Yes

2614 (66.6)

49.2. (48.6, 49.8)***

49.2 (48.6, 49.7)***

49.1 (48.5, 49.7)***

48.8. (48.2, 49.3)***

48.6 (47.0, 49.2)***

No

1312 (33.4)

51.6 (50.8, 52.4)

51.7 (50.8, 52.5)

51.8 (51.0, 52.7)

52.4 (51.5, 53.3)

55.6 (54.4, 56.9)

Year of assessment

      

2003-2005

1640 (41.8)

50.0 (49.2, 50.7)**

50.3 (49.5, 51.0)*

50.6 (49.8, 51.3)*

51.1 (50.4, 51.9)***

51.3 (50.4, 52.2)***

2006-2008

957 (24.4)

48.9 (47.9, 49.8)

49.0 (48.0, 49.9)

49.0 (48.1, 50.0)

49.1 (48.1, 50.0)

48.9 (47.7, 50.0)

2009-2011

1329 (33.8)

50.8 (50.0, 51.6)

50.4 (49.6, 51.2)

50.0 (49.2, 50.8)

49.3 (48.5, 50.1)

49.2 (48.3, 50.1)

  1. aPattern stands for Bayesian Expected a Posteriori (EAP) score; as many different score estimates were produced for each raw PSS score as the number of item response combinations yielding the PSS score.
  2. bSummed stands for EAP Summed Score; only one summary EAP Summed Score was generated for each raw PSS score.
  3. *P < 0.05; **P < 0.01; ***P < 0.001.
  4. Note. The scores of global disability, residual physical disability, and residual mental disability are all reported as scaled scores (S) with mean 50 and SD 15, but they are not on the same metric. All the scores of global disability are directly comparable, but not the scores of residual physical disability and residual mental disability. For instance, because the SD of the score of global disability is much larger than that of the scores of physical and mental disability, a score of global disability of S = 70 represents much more disability than a score of residual physical, or mental, disability of S = 70.
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BMC Neurology

ISSN: 1471-2377

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