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Key opinion leaders discuss how to recognize, confirm, and treat CIDP

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Distinguishing Inflammatory Neuropathies

Mark B. Bromberg, MD, PhD, Neurology, discusses criteria for primary demyelination, sensitivity of CIDP criteria, and EFNS criteria for confirmation.

Transcript

Distinguishing Inflammatory Neuropathies

Mark B. Bromberg, MD, PhD, Neurology, discusses criteria for primary demyelination, sensitivity of CIDP criteria, and EFNS criteria for confirmation.

My name is Mark Bromberg. I'm a professor of neurology at the University of Utah. I began my career with a doctoral degree in neurophysiology, and when I decided to go into clinical medicine, I chose neurology with a subspecialization in nerve and muscle disorders and clinical neurophysiology.

Today I would like to talk to you about using electrodiagnostic criteria for distinguishing amongst inflammatory neuropathies, and in particular CIDP. When we are evaluating patients for suspected CIDP and do our nerve conductions, we would like to have a set of criteria to refer back to, to determine whether they have evidence for primary demyelination.

One question is, "How did people originate these criteria?" Well, in the very beginning, they used some data from primary axonal neuropathies to see what the limits were from axonal loss. And then from their experience, they came up with the expected changes for demyelination, and this would represent expert opinion. And then they did some modeling studies using animal wave forms or human wave forms, and then they came up with a set of criteria. Then they took a group of patients who fulfilled the clinical features of CIDP—that is, they had the history of the chronic duration, they had the proximal and distal weakness, and they had the response to therapy. Then they looked at their nerve conduction numbers to see how many of those fulfilled the criteria they established, and if the percentage wasn't high, then they made small adjustments in the criteria.

Then another group would take their patients with clinical CIDP, see how they fit into the criteria, and then they made more adjustments. So now you have 2 sets of criteria. And this went on and on, and so you can see that both for Guillain-Barré or AIDP and CIDP, people have evolved a number of sets of criteria. For CIDP, it's over 16. You can see that the sensitivity as they're applied to groups of patients with a clinical diagnosis ranges from low of 11% to about 95%.

So one question is, "Overall, which set of criteria is most useful to use?" Also, I want you to keep in mind that the criteria were primarily for research, so that if you want to do a drug trial on patients with CIDP, you want to make sure that they all fulfill a criteria so you're dealing with a uniform set of patients. However, applying these criteria can be useful in the clinic if you're making a diagnosis for your own patient and not part of a trial.

So one group has taken all the criteria and applied them to their set of patients to show you the sensitivity here, and it's an EF and S criteria, have a high degree of sensitivity, and also a high degree of specificity. These are the criteria of all those you see that have evolved over time that are generally used for research.

Now, these criteria are relatively complicated, and so here you can see the criteria for definite CIDP. And so these can be a bit onerous to apply when you're in the laboratory. When you do your nerve conduction studies, the EMG machines will set the markers for the latency of the response, for the amplitude of the response, and for the duration of the response. You see here a very low amplitude response, where the appropriate duration on the right is at the very end of the up and down wave forms. However, initially using the machine algorithm, it's set at much shorter as you can see with the red arrow. So you always must check the wave forms before you rely on the table of values to make sure that you agree with the markers as they were set by the EMG machine.

Thank you, and I hope that my talk with you today has helped you understand how to use nerve conduction studies to confirm the diagnosis of CIDP.

Transcript

Distinguishing Inflammatory Neuropathies

Mark B. Bromberg, MD, PhD, Neurology, discusses criteria for primary demyelination, sensitivity of CIDP criteria, and EFNS criteria for confirmation.

My name is Mark Bromberg. I'm a professor of neurology at the University of Utah. I began my career with a doctoral degree in neurophysiology, and when I decided to go into clinical medicine, I chose neurology with a subspecialization in nerve and muscle disorders and clinical neurophysiology.

Today I would like to talk to you about using electrodiagnostic criteria for distinguishing amongst inflammatory neuropathies, and in particular CIDP. When we are evaluating patients for suspected CIDP and do our nerve conductions, we would like to have a set of criteria to refer back to, to determine whether they have evidence for primary demyelination.

One question is, "How did people originate these criteria?" Well, in the very beginning, they used some data from primary axonal neuropathies to see what the limits were from axonal loss. And then from their experience, they came up with the expected changes for demyelination, and this would represent expert opinion. And then they did some modeling studies using animal wave forms or human wave forms, and then they came up with a set of criteria. Then they took a group of patients who fulfilled the clinical features of CIDP—that is, they had the history of the chronic duration, they had the proximal and distal weakness, and they had the response to therapy. Then they looked at their nerve conduction numbers to see how many of those fulfilled the criteria they established, and if the percentage wasn't high, then they made small adjustments in the criteria.

Then another group would take their patients with clinical CIDP, see how they fit into the criteria, and then they made more adjustments. So now you have 2 sets of criteria. And this went on and on, and so you can see that both for Guillain-Barré or AIDP and CIDP, people have evolved a number of sets of criteria. For CIDP, it's over 16. You can see that the sensitivity as they're applied to groups of patients with a clinical diagnosis ranges from low of 11% to about 95%.

So one question is, "Overall, which set of criteria is most useful to use?" Also, I want you to keep in mind that the criteria were primarily for research, so that if you want to do a drug trial on patients with CIDP, you want to make sure that they all fulfill a criteria so you're dealing with a uniform set of patients. However, applying these criteria can be useful in the clinic if you're making a diagnosis for your own patient and not part of a trial.

So one group has taken all the criteria and applied them to their set of patients to show you the sensitivity here, and it's an EF and S criteria, have a high degree of sensitivity, and also a high degree of specificity. These are the criteria of all those you see that have evolved over time that are generally used for research.

Now, these criteria are relatively complicated, and so here you can see the criteria for definite CIDP. And so these can be a bit onerous to apply when you're in the laboratory. When you do your nerve conduction studies, the EMG machines will set the markers for the latency of the response, for the amplitude of the response, and for the duration of the response. You see here a very low amplitude response, where the appropriate duration on the right is at the very end of the up and down wave forms. However, initially using the machine algorithm, it's set at much shorter as you can see with the red arrow. So you always must check the wave forms before you rely on the table of values to make sure that you agree with the markers as they were set by the EMG machine.

Thank you, and I hope that my talk with you today has helped you understand how to use nerve conduction studies to confirm the diagnosis of CIDP.


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Thrombosis may occur with immune globulin products, including GAMUNEX-C. Risk factors may include: advanced age, prolonged immobilization, hypercoagulable conditions, history of venous or arterial thrombosis, use of estrogens, indwelling central vascular catheters, hyperviscosity, and cardiovascular risk factors. Thrombosis may occur in the absence of known risk factors. For patients at risk of thrombosis, administer GAMUNEX-C at the minimum dose and infusion rate practicable. Ensure adequate hydration in patients before administration. Monitor for signs and symptoms of thrombosis and assess blood viscosity in patients at risk for hyperviscosity.

Renal dysfunction, acute renal failure, osmotic nephrosis, and death may occur with immune globulin intravenous (IVIG) products in predisposed patients. Patients predisposed to renal dysfunction include those with any degree of preexisting renal insufficiency, diabetes mellitus, age greater than 65, volume depletion, sepsis, paraproteinemia, or patients receiving known nephrotoxic drugs. Renal dysfunction and acute renal failure occur more commonly in patients receiving IVIG products containing sucrose. GAMUNEX-C does not contain sucrose. For patients at risk of renal dysfunction or failure, administer GAMUNEX-C at the minimum concentration available and the minimum infusion rate practicable.

GAMUNEX-C is contraindicated in patients who have had an anaphylactic or severe systemic reaction to the administration of human immune globulin. It is contraindicated in IgA-deficient patients with antibodies against IgA and history of hypersensitivity.

Severe hypersensitivity reactions may occur with IVIG products, including GAMUNEX-C. In case of hypersensitivity, discontinue GAMUNEX-C infusion immediately and institute appropriate treatment.

Monitor renal function, including blood urea nitrogen (BUN), serum creatinine, and urine output in patients at risk of developing acute renal failure.

Hyperproteinemia, increased serum viscosity, and hyponatremia may occur in patients receiving IVIG treatment, including GAMUNEX-C.

There have been reports of aseptic meningitis, hemolytic anemia, and noncardiogenic pulmonary edema (transfusion-related acute lung injury [TRALI]) in patients administered with IVIG, including GAMUNEX-C.

The high-dose regimen (1g/kg x 1-2 days) is not recommended for individuals with expanded fluid volumes or where fluid volume may be a concern.

Because GAMUNEX-C is made from human blood, it may carry a risk of transmitting infectious agents, eg, viruses, the variant Creutzfeldt-Jakob disease (vCJD) agent, and, theoretically, the Creutzfeldt-Jakob disease (CJD) agent.

Do not administer GAMUNEX-C subcutaneously in patients with ITP because of the risk of hematoma formation.

Periodic monitoring of renal function and urine output is particularly important in patients judged to be at increased risk of developing acute renal failure. Assess renal function, including measurement of BUN and serum creatinine, before the initial infusion of GAMUNEX-C and at appropriate intervals thereafter.

Consider baseline assessment of blood viscosity in patients at risk for hyperviscosity, including those with cryoglobulins, fasting chylomicronemia/markedly high triacylglycerols (triglycerides), or monoclonal gammopathies, because of the potentially increased risk of thrombosis.

If signs and/or symptoms of hemolysis are present after an infusion of GAMUNEX-C, perform appropriate laboratory testing for confirmation.

If TRALI is suspected, perform appropriate tests for the presence of antineutrophil antibodies and anti-HLA antibodies in both the product and patient's serum.

After infusion of IgG, the transitory rise of the various passively transferred antibodies in the patient's blood may yield positive serological testing results, with the potential for misleading interpretation.

In clinical studies, the most common adverse reactions with GAMUNEX-C were headache, pyrexia, hypertension, chills, rash, nausea, arthralgia, and asthenia (in CIDP); cough, rhinitis, pharyngitis, headache, asthma, nausea, fever, diarrhea, and sinusitis with intravenous use (in PIDD) and local infusion-site reactions, fatigue, headache, upper respiratory tract infection, arthralgia, diarrhea, nausea, sinusitis, bronchitis, depression, allergic dermatitis, migraine, myalgia, viral infection, and pyrexia with subcutaneous use (in PIDD); and headache, ecchymosis, vomiting, fever, nausea, rash, abdominal pain, back pain, and dyspepsia (in ITP).

The most serious adverse reactions in clinical studies were pulmonary embolism (PE) in 1 subject with a history of PE (in CIDP), an exacerbation of autoimmune pure red cell aplasia in 1 subject (in PIDD), and myocarditis in 1 subject that occurred 50 days post-study drug infusion and was not considered drug related (in ITP).

Please see accompanying full Prescribing Information for GAMUNEX-C.

Terms to know

IG=immune globulin, CIDP=chronic inflammatory demyelinating polyneuropathy, PIDD=primary immunodeficiency disease, ITP=idiopathic thrombocytopenic purpura, Sub Q=subcutaneous, IV=intravenous, ICE=10% caprylate-chromatography purified immune globulin intravenous (IGIV-C) CIDP efficacy.

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