Table 1

Clinical characteristics of subjects and muscle [18F]florbetapir uptake values

IBM
(n=10)
PM
(n=6)
P value
Mean age in years at diagnosis (SD)64.3 (8.4)58.2 (10.7)0.222*
Mean age in years at scan (SD)68.3 (8.0)59.7 (11.1)0.092*
Mean disease duration at scan in years (SD)4.0 (3.0)1.5 (1.4)0.079*
Gender (Male | Female)9 | 14 | 2 0.036
Mean manual muscle testing score (0–260) (SD)236 (22.9)256 (2.3)0.052*
Mean Health Assessment Questionnaire disability index (SD)1.3 (0.7)0.8 (0.8)0.192*
Mean IBM-Functional Rating Scale (0–40) (SD)28.9 (5.3)
Mean physician global disease activity VAS (0–10) (SD)1.8 (1.5)
Mean serum total creatine kinase level (IU/L) (SD)579 (408)‡308 (220)
Current immunosuppressive treatments (n)NilPrednisolone (5/6)
Methotrexate (2/6)
Azathioprine (2/6)
Cyclophosphamide (1/6)
Previous immunosuppressive treatments (n)Prednisolone (3/10)
Azathioprine (1/10)
Mycophenolate (1/10)
Cyclophosphamide (2/6)
Prednisolone (1/6)
Mycophenolate (1/6)
Azathioprine (1/6)
Ciclosporin (1/6)
IVIG (1/6)
Median [18F]florbetapir SUV (IQR)Left arm0.47
(0.41–0.55)
0.40
(0.36–0.48)
0.104§
Right forearm0.39
(0.35–0.42)
0.32
(0.27–0.40)
0.104§
Left forearm0.45
(0.32–0.55)
0.33
(0.30–0.36)
0.129§
Right thigh¶0.44
(0.43–0.52)
0.41
(0.37–0.45)
0.288§
Left thigh¶0.48
(0.43–0.51)
0.41
(0.36–0.45)
0.059§
Right calf0.51
(0.45–0.61)
0.46
(0.44–0.50)
0.233§
Left calf0.51
(0.40–0.58)
0.43
(0.39–0.45)
0.233§
Overall (total-SUV)0.48
(0.44–0.51)
0.42
(0.39–0.45)
0.039§
Median [18F]florbetapir SUVR (IQR)Left arm¶1.61
(1.43–1.81)
0.96
(0.82–1.08)
0.002§
Right forearm1.26
(1.05–1.60)
0.79
(0.67–0.91)
0.005§
Left forearm1.26
(1.12–1.52)
0.83
(0.58–0.96)
0.005§
Right thigh**1.34
(1.31–1.77)
1.04
(0.79–1.21)
0.013§
Left thigh**1.40
(1.40–1.87)
0.99
(0.79–1.18)
0.005§
Right calf1.59
(1.36–2.29)
1.09
(0.94–1.35)
0.013§
Left calf1.56
(1.29–2.40)
1.00
(0.75–1.31)
0.030§
Overall (total-SUVR)1.45
(1.28–2.05)
1.01
(0.80–1.22)
0.005§
  • Bold values indicate statistically significant differences.

  • *P values derive from two-sided students t-test.

  • †Fisher’s exact test.

  • ‡For the IBM group, this refers to the peak serum creatine kinase level (it was not rechecked at the time of the scan).

  • §The Mann-Whitney Ranksum test.

  • ¶The right arm was not used because radiotracer administration was via a venous cannula in the right antecubital fossa, except in two subjects (one with PM, one with IBM) where the reverse was true due to difficulties with cannula placement.

  • **n=9 for IBM group. Measurement in one subject could not be obtained due to very high levels of muscle atrophy and fatty replacement.

  • IBM, inclusion body myositis; IVIG, intravenous immunoglobulin; PM, polymyositis; SUV, standardised uptake value; SUVR, standardised uptake value ratio with reference region in lumbar fat pad; VAS, visual analogue scale.