Using Serologic Screening To Identify And Monitor At-Risk Charcot Patients

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Continuing Education Course #122 — August 2004

I am pleased to introduce the latest article, “Using Serologic Screening To Identify And Monitor At-Risk Charcot Patients,” in our CE series. This series, brought to you by the North American Center for Continuing Medical Education, consists of regular CE activities that qualify for one continuing education contact hour (.1 CEU). Readers will not be required to pay a processing fee for this course.

Timely diagnosis and subsequent treatment are essential when it comes to Charcot neuroarthropathy. With this in mind, Molly Judge, DPM, a Fellow of the American College of Foot and Ankle Surgeons, and a certified nuclear medicine technologist, provides a thorough overview of serologic screening, with a specific emphasis on the use of the erythrocyte sedimentation rate and C-reactive protein.

At the end of this article, you’ll find a 10-question exam. Please mark your responses on the enclosed postcard and return it to HMP Communications. This course will be posted on Podiatry Today’s Web site (www.podiatrytoday.com) roughly one month after the publication date. I hope this CE series contributes to your clinical skills.

Sincerely,

Jeff A. Hall
Editor-In-Chief
Podiatry Today

INSTRUCTIONS: Physicians may receive one continuing education contact hour (.1 CEU) by reading the article on pg. 76 and successfully answering the questions on pg. 82. Use the enclosed card provided to submit your answers or fax the form to NACCME at (610) 560-0502.
ACCREDITATION: The North American Center for Continuing Education (NACCME) is approved by the Council on Podiatric Medical Education as a sponsor of continuing education in podiatric medicine.
DESIGNATION: This activity is approved for 1 continuing education contact hour or .1 CEU.
DISCLOSURE POLICY: All faculty participating in Continuing Education programs sponsored by the NACCME are expected to disclose to the audience any real or apparent conflicts of interest related to the content of their presentation.
DISCLOSURE STATEMENTS: Dr. Judge has disclosed that she has no significant financial relationship with any organization that could be perceived as a real or apparent conflict of interest in the context of the subject of her presentation.
GRADING: Answers to the CE exam will be graded by the NACCME. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam.
TARGET AUDIENCE: Podiatrists.
RELEASE DATE: August 2004.
EXPIRATION DATE: August 31, 2005.
LEARNING OBJECTIVES: At the conclusion of this activity, participants should be able to:
• describe how the C-reactive protein (CRP) correlates with the occurrence and resolution of clinical disease;
• discuss possible non-infectious reasons for CRP elevation;
• discuss the diagnostic merits of the erythrocyte sedimentation rate (ESR); and
• compare and contrast the CRP with the ESR.

Sponsored by the North American Center for Continuing Medical Education.

Here one can see midfoot collapse resulting in a prominent plantarflexed cuboid for a patient who has a history of Charcot foot. While he has had a red, hot and swollen foot for approximately three weeks, he denies any recent injury. Note the erythematous
This lateral radiograph shows  the rocker bottom configuration that resulted from an acute Charcot flare. End-stage degenerative changes permeate the midfoot. Serologic testing, particularly the CRP, can be helpful in determining the intensity of the infe
This MRI STIR technique identifies the region of a loculated abscess formation that rests immediately beneath the remnant of cuboid bone. Note the intermedullary edema indicated by the increased signal intensity within the adjacent osseous structures of t
This MRI T1 image conveys the necrotic changes associated with osteomyelitis in the cuboid bone. The decreased signal intensity in the cuboid is classic for the degenerative changes that occur in both bone infection and neuropathic bone.
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Author(s): 
By Molly S. Judge, DPM

Charcot neuroarthropathy and the complications of longstanding diabetes are perhaps the greatest challenge for the foot and ankle specialist. These conditions are of principal concern given the limb threatening consequences when a diagnosis of Charcot foot is delayed or missed completely. Though there is no modern revelation in identifying the Charcot foot, there has been rejuvenated interest behind the continued study of this neuropathic entity.1-22 Subsequently, the slow rise in the number of reported cases of Charcot neuroarthropathy is likely due more to increased awareness of the disease as opposed to an increased incidence.
An increase in the reported incidence of Charcot neuroarthropathy will also likely occur as clinicians emphasize more due diligence in identifying the “at risk” population. Serologic screening is integral to identifying these “at risk” individuals. Indeed, when an acute Charcot flare occurs, there is a disruption of normal homeostasis that is reflected by changes within the blood serum. With this in mind, clinicians should complete a serum screening as soon as possible when they suspect Charcot foot.
Given the many possible etiologies for neuroarthropathy, one should pay particularly close attention to determining the cause of the disease among patients who present with clinical and radiographic evidence of an osteolytic process.23,24 Most importantly, one should establish a differential diagnosis, ruling out those diagnoses with the highest associated morbidity including the limb-threatening conditions of septic arthritis, osteomyelitis and Charcot neuroarthropathy. These destructive processes often coexist so one must address the possible combination of a neuropathic osteolytic process and infection. Modern technology allows the study of many serologic markers that flag pertinent systemic changes associated with neuropathic osteolysis and osteomyelitis.25 Such changes are the result of uncontrolled hyperglycemia, bone destruction, inflammation and infection.

To help differentiate between bone destruction secondary to Charcot neuroarthropathy and osteolysis due to infection, there are many cursory serologic studies that are commonly utilized. These studies include: leukocyte count with differential, platelet and reticulocyte counts, alkaline phosphatase, calcium, albumin, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). There are also studies such as hemoglobin A-1C for assessing the degree of glycemic control.
The importance of these studies is well understood and they each have very practical application when one suspects an infection in the Charcot foot. While CRP and ESR are the diagnostic workhorses when it comes to this clinical scenario, the actual physiologic mechanism that drives these studies is often poorly understood. Subsequently, clinicians may mistakenly use these tests interchangeably. What many do not understand is that there is a distinct benefit in monitoring the C-reactive protein when it comes to differentiating between neuropathic osteolysis and infection.

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