A 55-year-old woman presents to your office with painful hands, causing difficulty opening jars and turning the key in the ignition of her car. She is fatigued and she notices joint stiffness, but limbers up by lunch. She has trouble getting her rings off because of enlarging knuckles. About a year ago, she tried some OTC ibuprofen, which seemed to help, but led to the development of a bleeding ulcer severe enough to require transfusion and ICU care. Otherwise, her health is good, and her review of systems is negative. Your physical examination reveals tenderness and swelling at the index proximal interphalangeal and metacarpophalangeal joints bilaterally. There are small effusions on both knees. She has tenderness to lateral compression of the forefoot area bilaterally.
Which of the following tests is most likely to result in a diagnosis?
- joint aspiration
- ESR
- serum uric acid
- rheumatoid factor
- ACE level
Answer(s): D
Explanation:
In all likelihood, this patient is presenting with a systemic inflammatory arthritis. Clearly, treatment will need to be initiated. In order to effectively and promptly treat her, you will need to understand the current state of her physiology. Therefore, basic laboratory studies including blood count, full chemistries, and urinalysis should be obtained. At this point, the most likely diagnosis is RA, and the rheumatoid factor and sedimentation rate may be helpful. Theoretically, sarcoidosis can present in this way but, epidemiologically, this is much less likely. Because of this and because the ACE level is fairly nonspecific, it should not be part of the initial workup. Neither joint fluid aspiration nor uric acid levels are likely to be diagnostic. The elevation of serum transaminase in the face of elevated sedimentation rate, moderate or low positive ANA, and rheumatoid factors raise the question about hepatitis C.
About 50% of patients with active hepatitis C will have cryoglobulinemia. Cryoglobulins can produce low moderate positive rheumatoid factors. Therefore, it is extremely important in this circumstance to be certain that hepatitis C is not present. With such a low positive ANA, the likelihood that this is classical Lupus is low, and double-stranded DNA antibodies are not likely to be revealing. C-reactive protein may confirm the presence of inflammation, but it won't provide additional information over the sedimentation rate. Syphilis, "the great imitator," again may occasionally have arthritis as a manifestation--but rarely without other features. The remaining studies while they might be useful later but are unlikely to be helpful as the next most important test obtained. The probable source of the patient's symptoms is RA. Osteoarthritis can produce articular swelling, but on physical examination, there is rarely bogginess in the synovium. Anti- CCP antibody is an antibody directed against the citrullinated portion of fillagen. It has the highest specificity for RA of any antibody known. It is usually present early and may predict more severe disease.
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