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Table 3 Associations between true positive myositis-specific and myositis-associated autoantibodies and clinical factors

From: Line blot immunoassays in idiopathic inflammatory myopathies: retrospective review of diagnostic accuracy and factors predicting true positive results

FactorAny true positive MSA/MAAAny false positive MSA/MAAORPCI
Female gender78% (80/103)67% (50/75)1.740.100.89–3.39
Mean age of onset (SD)50 (13)52 (15)0.990.350.96–1.01
Pre-test working diagnosis of IIM59% (61/103)19% (14/75)50.8<0.00113.66–189.22
Biopsy in keeping with inflammatory myopathy50% (7/14)28% (7/25)2.570.180.66–10.06
Myopathic EMG changes64% (21/33)43% (12/28)2.330.110.83–6.54
Highest recorded CK (mean, SD)1377 (3502)563 (910)1.00.1081.00–1.00
Strong positive antibody result70% (72/103)35%
26/75
4.38<0.0012.32–8.26
  1. MSA myositis-specific autoantibody, MAA myositis-associated autoantibody, OR odds ratio, P p-value, CI confidence intervals, SD standard deviation, IIM idiopathic inflammatory myopathy, EMG electromyography, CK creatine kinase