1st order laboratory parameters – obligatory laboratory tests.
- Small blood count, differential blood count [leukocytosis with left shift (may occur)]
- Inflammatory parameters – CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate).
- Muscle enzymes
- Creatine kinase (CK) [↑]
- Aldolase [↑]
- GOT [↑]
- Lactate dehydrogenase (LDH) [↑]
- Possibly detection of myoglobin in serum and urine.
- Immunological parameters
- ANF titer [negative]
- Antinuclear antibodies (ANA) [approximately 50% of cases]
- Anti-Jo-1 (antibody against histidyl transfer RNA synthetase) [approximately 5% of cases]
- Anti-Mi2 [10% of cases]
- Anti-PmScl [10% of cases]
- U1-RNP [15% of cases]
- Anti-SRP [approximately 5% of cases, often with cardiac involvement]
- Direct immunofluorescence (DIF) [frequently positive]
- Muscle biopsy (key diagnostic measure) – measurement of histologic and biochemical characteristics; determines pathologic (disease-related) changes in tissue:
- Lymphocytic infiltration (invasion of T lymphocytes) with fibrous degeneration.
- Regeneration of muscle fibers
- Accumulation of T-lymphocytes (in and v. a. between the muscle fibers).
