Q:

11/8/2013
Do you have an easy-to-read resource explaining the difference between the C1 inhibitor functional assay by ELISA and the chromoogenic C1 inhibitor functional assay, or would you be able to explain how these two assays differ? I do not have access to the journal cited in the HAE practice parameter (Wagenaar-Bos IG, Drouet C, Aygoren-Pursun et al). Although everyone knows the chromogenic assay is superior, I am embarrassed to admit I do not know why the chromogenic assay is superior! Any help would be appreciated.

A:

Thank you for your inquiry.

I am referring your question to Dr. Allen Kaplan, who is, as you know, an international expert in the diagnosis of angioedema by laboratory measurements. As soon as we hear from Dr. Kaplan, we will forward his response to you.

Thank you again for your inquiry.

Sincerely,
Phil Lieberman, M.D.

We have received a response from Dr. Allen Kaplan/Dr. Kusumam Joseph to your Ask the Expert inquiry. Thank you again for your inquiry and we hope this response is helpful to you.

Sincerely,
Phil Lieberman, M.D.

Response from Drs. Allen Kaplan and Kusumam Joseph:
The chromogenic assay measures the inhibition of C1s activity by plasma C1 inhibitor. The ELISA assay detects the complexes formed between C1-INH and C1r or C1s following activation of C1. The chromogenic assay is recommended based on "the high sensitivity, clear distinction and low variability". The reference paper is below.

Functional C1-Inhibitor diagnostics in hereditary angioedema: Assay evaluation and recommendations
 
Sincerely,
Drs. Kusumam Joseph and Dr. Allen Kaplan

AAAAI - American Academy of Allergy Asthma & Immunology