Guide to blood tests in rheumatology
- Please perform, CRP (and consider PV if CRP normal) as discrepancy can be useful information.
- Beware CRP rises with increasing BMI.
- PV can be affected by age, exercise, smoking and pregnancy.
- CRP typically normalises faster than PV on treating PMR/GCA
- Normal inflammatory markers can be seen in inflammatory arthritis. If clinical suspicion remains high despite normal blood tests then refer ( this is especially true in psoriatic arthritis).
- Can be positive in 5-20% normal population, especially at low titres (11-30).
- 70% of patients with RA will have positive RhF and 90% of patients with Sjorgens.
- RhF can be negative in Rheumatoid arthritis so if strong clinical suspicion still refer.
Anti-CCP ( Anticycylic citrullinated peptide)
- More specific for RA but can only be requested by secondary care
ANA ( Antinuclear antbodies)
- Only check if Autoimmune disease is suspected, ie. Symptoms include inflammatory arthritis, myalgias, rashes, mouth ulcers, recurrent serositis (pericarditis and pleurisy), and sicca symptoms (dry eyes and mouth).
- Prevalence of ANA in healthy people (3-30%), with higher levels in women and with increasing age.
- Even at high titres (>1:160), a positive ANA result alone does not indicate Autoimmune disease.
- Other conditions associated with positive ANA, include viral infections and cancers.
- Raised levels associated with gout
- Levels can be normal in gout especially at the time of acute attack
Arthritis Research UK- Approach to polyarthralgia ,2012; Gout 2016
American college of Rheumatology, Patient information-2015
Guidelines reviewed 06/01/2020
Next review due 06/01/2021
GP Sifter Dr B Wesson ( RMS GP Lead for Rheumatology)