Table 3

The muscle strength, disease activity and damage scores, and twitch interpolation results of patients with myositis
QF (MVC) Strength category
 Patient number
 QF mass-normalised force F/LBM (N/kg)
 Activity status
 Damage score (0–3)
 Twitch status (-/+)
"Not weak"
 1
 8.83
 Inactive
 0
 -

2
 7.17
 Active -
 1
 -

4
 5.64
 Active -
 1
 -

5
 5.63
 Inactive
 1
 -

6
 5.40
 Inactive
 1
 -

3
 6.40
 Inactive
 2
 +
"Weak"
 7
 4.14
 Active -
 1
 -

8
 3.97
 Active -
 1
 -

9
 3.69
 Active
 1
 -

11
 2.82
 Active
 1
 -

12
 2.28
 Inactive
 3
 -

14
 2.10
 Active
 1
 -

*17
 1.30
 Active
 3
 -

*19
 0.99
 Inactive
 3
 -

10
 3.32
 Active
 1
 +

13
 2.11
 Active -
 2
 +

15
 1.84
 Active -
 3
 +

16
 1.76
 Active -
 1
 +

18
 1.00
 Active +
 2
 +

20
 0.80
 Inactive
 3
 +

Twenty patients with myositis listed according to their mass-normalised strength and twitch interpolation results, and stratified as "not weak" and "weak" according to their F/LBM results (see text). In general terms, as QF strength decreased, the incidence of positive twitches increased. Cases 17 and 19 had had muscle biopsies within the previous 6 months, and the results showed end-stage disease with severe muscle atrophy and fibrosis. F/LBM, force per units of lean body mass; MVC, maximum voluntary contraction; QF, quadriceps femoris.

Molloy et al. Arthritis Research & Therapy 2006 8:R67   doi:10.1186/ar1935

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