Aquaporin-4 antibody in neuromyelitis optica: re-testing study in a large population from China

ABSTRACT

Background: Aquaporin-4 (AQP4) antibody sero-positivity is critically important in neuromyelitis optica (NMO). However, the sensitivity of different assays is highly variable. Repeating detection with a highly sensitive assay in a large population is necessary in the case of so-called negative NMO. Methods: Retrospective analysis where AQP4 antibodies were detected by commercial cell-based assay (CBA), in-house M23-CBA and in-house M1-CBA. Results: Of the 1011 serum samples, 206 (20.4%) were sero-positive by primary commercial CBA. In the retest, all 206 participants positive by primary commercial CBA also yielded positive results by in-house M23-CBA and the second commercial CBA again, but only 124 positive in in-house M1-CBA. Among the 805 participants negative by primary commercial CBA, 71 participants were positive for in-house M23-CBA, of which 20 participants were positive for the second commercial CBA, and none were positive by in-house M1-CBA. Of the 171 cerebral spinal fluid samples, 75 (43.9%) were positive by primary commercial CBA. All 75 participants positive by primary commercial CBA also yielded positive results by in-house M23-CBA and the second commercial CBA. Forty-nine (65.3%) of these 75 participants were positive by in-house M1-CBA. Among the 96 participants negative by primary commercial CBA, 15 participants were positive for in-house M23-CBA and none were positive by in-house M1-CBA and the second commercial CBA. Conclusions: Different AQP4 isoforms in CBA result in different detection effects, and in-house M23-CBA is the most sensitive method. Some AQP4 antibody–negative NMO may be subject to diagnostic uncertainty due to limitations of the assays.

KEYWORDS:

• Neuromyelitis optica
• aquaporin-4
• test
• diagnosis

Acknowledgments

We are very grateful to Ms Jinmei Lin (MSSbio company, Guangzhou, China) for the help of transfection of HEK-293 cells. We also are very grateful to the following department for samples collection. They include: Department of Neurology, The Chinese Medicine Hospital of Nanhai city; Department of Neurology, The Chinese Medicine Hospital of Zhongshan city; Department of Neurology, The Zhongshan Peoples Hospital; Department of Neurology, The First Affiliated Hospital of GuangDong Pharmaceutical University; Department of Neurology, The Eighth Peoples Hospital of Guangzhou; Department of Neurology, The First Affiliated Hospital of GuangZhou Medical University; Department of Neurology, The Guangzhou General Hospital of Guangzhou Military Command; Department of Neurology, The Guangzhou Women and Children Medical Center; Department of Neurology, The Guangzhou Brain Hospital; Department of Neurology, The Chinese Medicine Hospital of Guangdong Province; Department of Neurology, The Fourth Affiliated Hospital of GuangZhou Medical University; Department of Neurology, The Guangzhou Red Cross Hospital; Department of Neurology, The Boai Hospital of Zhongshan.

Declaration of Interest

No potential conflict of interest was reported by the authors. This study was supported by the Natural Science Foundation of Guangdong Province [grant number 2014A030313499]; Science and Technology Plan Project of Guangdong Province [grant number 2014A020212332].

Additional information

Funding

This study was supported by the Natural Science Foundation of Guangdong Province [grant number 2014A030313499]; Science and Technology Plan Project of Guangdong Province [grant number 2014A020212332].