Case 4: Diagnostic Testing

Click to reveal results!
Basic laboratory results
Choose the most high yield diagnostic tests to perform next!
Rheumatoid factor and anti-CCP
Correct! RA is on the top of our differential diagnosis and we should definitely check antibodies associated with it. Of note, seropositivity is not required for RA diagnosis but helpful diagnostically and prognostically as higher titers are associated with higher risk of extra-articular manifestations and erosive disease.
Correct! Inflammatory markers are non-specific but help us monitor disease activity. Be careful though – normal inflammatory markers do not mean that patient does not have inflammation. Your H&P are much more important in determining that.
X-rays hands and feet
Correct! Since we suspect inflammatory arthritis, we would like to look for inflammatory changes on XR: loss of joint space, periarticular osteopenia, erosions, subluxation. The patient is young with recent onset of symptoms so her X-rays are more likely to be completely normal. Point-of-care ultrasound can also be useful in evaluating patient’s joints and detecting active synovitis and chronic inflammatory changes, such as synovial hypertrophy.
Uric acid
Incorrect! Patient is a young woman with symmetric polyarticular arthritis making gout very unlikely.
Extractable nuclear antigens (ENA), e.g. SSA/SSB, Sm/RNP, and other ANA sub-serologies
Incorrect. At this point, the patient does not have any symptoms to suggest a particular non-RA connective tissue disease. It is not recommended to check sub-serologies without a positive ANA or suspicion for a particular disease process. for example, if she complained of dry eyes/dry mouth and had extensive dental disease or decreased salivary pooling, then it would be reasonable to send SSA/SSB (although, secondary Sjogren’s may also happen in RA). Check out our ANA tutorial here for more information on ANA and its sub-serologies.
Anti-nuclear antibodies (ANA)
Equivocal. Connective tissue disease can certainly present with inflammatory arthritis as a first manifestation. That said, if we get positive RA serologies, in the absence of symptoms suggestive of another CTD, checking ANA is unnecessary at this point. However, if RF and CCP are negative, then an argument for inflammatory arthritis associated with non-RA CTD could be made and sending off ANA would be reasonable. If ANA is negative, ENA would not be recommended at this point. However, careful history and physical with each visit to look for manifestations of other diseases associated with inflammatory arthritis would be important. Check out our inflammatory arthritis schema coming soon! If you have access to a rheumatologist, it is certainly acceptable to leave this decision up to them.
Hepatitis B serologies; HIV; QuantiFERON-TB gold
Correct! We are quite confident this patient has inflammatory arthritis and will likely need a DMARD (disease-modifying anti-rheumatic drug). Before administering immunosuppressive medications, it is important to make sure that the patient does not have hepatitis C, hepatitis B (surface Ag, surface Ab, core Ab), HIV, or latent Tb. Your friendly rheumatologist would appreciate it tremendously, if a new patient arrives with these studies done!

Click here to move on!

Case 4 Index
Case 4 Introduction
Case 4 Review of Systems
Case 4 Physical Exam
Case 4 Differential Diagnoses