1st order laboratory parameters – obligatory laboratory tests.
- D-dimers – acute diagnosis of suspected fresh venous thrombosis/pulmonary embolism (see also under “Physical examination“: Wells score to determine the clinical probability of venous thrombosis, DVT).
Laboratory parameters 2nd order – depending on the results of the history, physical examination, etc. – for differential diagnostic clarification.
- Small blood count
- Inflammatory parameters – CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate).
- Creatine kinase (CK) (isoenzyme CK-MM) – the most important parameter in the detection of muscle diseases (polymyositis, dermatomyositis, but also in infectious myositis)Attention! Even in healthy people after heavy muscle work (eg bodybuilders, high-performance athletes or construction workers), after i. m. (intramuscular) injections are found significantly elevated CK values (not infrequently up to 10 times the upper limit of the norm).In statin-treated patients should be discontinued at a CK increase above 4-5 times the norm or must be discontinued at a CK increase above 10 times the norm.
- Anti-citrulline antibodies – antibodies against cyclic citrullinated peptides (ACPA, CCP-Ak, anti-CCP) – in suspected rheumatoid arthritis (RA) [highest disease specificity and sensitivity!], these can in combination with rheumatoid factors increase the reliability of the diagnosis at an early stage of the diseaseAnti-citrulline antibodies are directed against proteins containing the rare amino acid citrulline. It has been demonstrated that the affected joint mucosa of patients with rheumatoid arthritis secretes citrullinated proteins, which are possibly responsible for the inflammatory reaction and the destruction of the tissue.Already in the early stage of RA, CCP-AK* are detectable in about 80 % (sensitivity (percentage of diseased patients in whom the disease is detected by the use of the test, i.e. a positive test result occurs) approx.75 %; specificity approx. 96 %). Thus, positive CCP-AK in diagnostically unclear cases and rheumatoid factor-negative patients represent a considerable diagnostic gain. Detected CCP-AK are almost considered proof of rheumatoid arthritis.
