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Overcoming the challenges in diagnosis of AQP4-IgG positive neuromyelitis, optica spectrum disorders in resource poor settings using an indigenized and cost effective cell based assay.

J Neuroimmunol 2021 Sep 2;360:577706. doi: 10.1016/j.jneuroim.2021.577706.

Lekha Pandit, Chaithra Malli , Anitha D’Cunha, Akshatha Sudhir


Background: Diagnosis of neuromyelitis optica spectrum disorders (NMOSD) in India is hindered by limited access to cost effective and sensitive assays for detection of aquaporin-4 antibody (AQP4-IgG) in India.

Objective: To develop a cost effective, sensitive, cell based assay (CBA) for detection of AQP4-IgG and to evaluate the serological status in patients with NMOSD diagnosed by 2015 diagnostic criteria.

Method: Stably transfected Chinese hamster ovary (CHO) cell line expressing aquaporin M23 isomer was established. A fixed CBA was developed and validated in 381 samples including clinically definite NMOSD (n = 87), high risk NMOSD (n = 51), other demyelinating disorders (n = 92), other neurological disorders (n = 51) and healthy volunteers (n = 100). We tested the same samples again using a commercially available CBA and compared the results. All assays were performed by 2 independent investigators blinded to clinical and serological status.

Results: Our “in house”(Mangalore) assay showed sensitivity of 81.6% (95% CI 71.86-89.11%) for clinically definite NMOSD and 29.41% (95% CI 17.50-43.8%) for high risk NMOSD. Specificity was 100% for both groups. Both assays showed similar results for 67/ 87 (77.01%) patients with definite NMOSD while 4 samples tested positive by our assay alone (Cohen’s kappa coefficient [K] – 0.86). Among the high risk group 14/51 (27.5%) samples showed similar results, one patient additionally was positive by the Mangalore assay (K – 0.95).

Keywords: AQP4-IgG; CHO-K1 cells; Cell based assay; NMOSD.