Letter to the Editor

Figures & data

Figure 1. (a) Recovery of IgE in relation to the concentration of the therapeutic antibody. (b) Degree of neutralization of IgE (omalizumab activity) or ability of the omalizumab IgE to bind as a function of the omalizumab level.

Table 1. Example of a measurement result from one serum sample.

free IgE	Recovery Value	IgE – Neutralization rate (activity)	Omalizumab
17.0 ng/mL	3.2%	96.8%	28.0 µg/mL

Table 2. Stability of equilibrium4.

Time [h]	16	20	22	24	Mean	C.V.
IgE [IU/mL]	O.D.	O.D.	O.D.	O.D.	O.D.	%
15	1.233	1.159	1.171	1.139	1.175	3.44
50	1.714	1.875	2.003	1.791	1.846	6.70
100	2.268	2.004	2.301	2.045	2.154	7.03

O.D., optical density; C.V., coefficient of variation.

Table 3. Inter-assay variance of recovery ELISA IgE/omalizumab5.

Sample	Mean IgE (IU/mL)	CV (%)	Mean Omalizumab (µg/mL)	CV (%)
1 (n = 12)	86.5	5.9	<LOQ	–
2 (n = 12)	44.7	9.6	17.4	13.2
3 (n = 12)	2.6	5.2	20.7	7.4
4 (n = 12)	22.3	9.4	45.2	12.9
5 (n = 12)	25.7	12.1	53.0	13.4

LOQ: Limit of quantification; CV: coefficient of variation.

Strohner P, Korn S, Buhl R, Becher G. The recovery-ELISA – a novel assay technique to monitor therapy with humanized antibodies: the example of omalizumab. J Immunoassay Immunochemistry 2013;34:83-93

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BioTeZ Berlin-Buch GmbH: RIO user manual – instructions for enzyme immunoassay for the quantitative in-vitro determination of free IgE and available therapeutic antibody omalizumab in human serum samples. Available at: http://www.biotez.de/index.php/de/unternehmen/downloads.html [Version 4, Last accessed 6 May 2014]

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