Table 3.

Diagnostic performance of different tests in the assessment of myopathy

Investigation	n	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
CK	627	54.5	77.8	55.8	76.9
Myositis antibodies	114	34.3	95.1	92.6	44.8
EMG	702	73.5	90.6	76.1	89.3
Muscle MRI	150	70.5	79.0	82.7	65.3
Biopsy	294	72.5	84.8	83.1	75.0
Genetics	176	37.0	75.7	51.9	62.9

Note: we have not included MRI neuroaxis as, although this was commonly requested, the test was not looking for evidence of myopathy but rather to exclude structural pathologies