Rheumatology Question 94

Answer & Critique 

Correct Answer: D

Educational Objective: Identify the cause of an elevated erythrocyte sedimentation rate.

Key Point

Noninflammatory conditions (kidney disease, diabetes mellitus, pregnancy, obesity) as well as normal aging can cause an elevated erythrocyte sedimentation rate.

Continuing this patient's current treatment is appropriate at this time. This patient has polymyalgia rheumatica (PMR); she feels well, and her laboratory studies have improved over time. Although her erythrocyte sedimentation rate (ESR) remains elevated, it likely does not represent ongoing disease activity. The most likely cause of this patient's persistently elevated ESR is her age; it may also be elevated because of uncontrolled diabetes mellitus (possibly exacerbated by prednisone). The degree of elevation is related to the serum globulin concentration, the albumin-globulin ratio, the serum fibrinogen concentration, and the percent of hemoglobin A1c but not the fasting serum glucose concentrations. ESR is dictated by characteristics of the erythrocytes themselves and by the presence of specific plasma proteins that alter the normal repulsive forces between erythrocytes and influence their ability to aggregate, form rouleaux, and sediment more quickly. These plasma proteins include acute phase reactants (such as fibrinogen) produced by the liver in response to proinflammatory cytokines occurring in rheumatologic disease, infection, and malignancy that neutralize these negative surface charges and increase ESR. Noninflammatory conditions causing elevated fibrinogen, including kidney disease, diabetes, pregnancy, and obesity, can also result in an elevated ESR. Normal aging can also cause an elevated ESR; for this female patient, an equation to find the estimate of the maximal expected ESR is (age in years + 10)/2, resulting in 42 mm/h.

It is important to recognize underlying factors that influence laboratory studies such as ESR; misinterpreting an elevated ESR as indicative of persistent inflammation or other disease can lead to inappropriate treatment such as prolongation or increase of glucocorticoid therapy. Thus, increasing prednisone or adding methotrexate is not indicated at this time.

This patient reports no headache, jaw claudication, or visual changes, all of which are clinical signs of giant cell arteritis; therefore, temporal artery biopsy is not indicated.

Bibliography

Colglazier C, Sutej P. Laboratory testing in the rheumatic disease: a practical review. South Med J. 2005 Feb;98(2):185-91. PMID: 15759949

This content was last updated in August 2015.

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