To develop a high sensitivity method to detect anti-MuSK antibody

Myasthenia gravis (MG) is an autoimmune disorder that causes weakness of voluntary muscles due to destruction of communication between muscle and nerves by autoantibodies. These antibodies form against acetylcholine receptor (AChR), muscle-specific kinase (MuSK), or other AChR-related proteins in the postsynaptic muscle membrane. Eighty percent of generalized MG patients have shown AChR antibody in their sera and, 4-10% of them have anti-MuSK antibody. While RIPA is the current golden standard diagnostic method to detect anti-MuSK antibody in patient sera, the sensitivity is just 50-60% and a complimentary approach with higher sensitivity is still needed.

Sera from 19 clinically definite MuSK MG patients and 20 healthy controls were tested for anti-MuSK antibody with live-Cell based assay (L-CBA) and MuSK RIPA at UBC laboratory.

Furthermore, 21 samples that are clinically definite MG patients but MuSK seronegative by RIPA and SPR were tested for MuSK Ab L-CBA.

Moreover, 20 samples that are clinically diagnosed as other neurological diseases,  non-MG were tested for MuSK Ab L-CBA.

All of samples were tested at 1:20 and 1:100 dilution.

0 out of 20 healthy controls and 12 out of 19 clinically definite MuSK MG patients were detected as positive for anti-MuSK antibody by both the L-CBA method, and the RIPA methods.

In the other cohort, MuSK Ab L-CBA detected 0 out of the 21 DSN-MG cases, and 2 out of 20 samples that are identified as non-MG.

It is noteworthy that both of these MuSK Ab L-CBA positive cases were identified as myopathy.

The effort to develop a higher sensitivity MuSK L-CBA is ongoing. MuSK L-CBA showed the same sensitivity and specificity in this study.