Establishment and consistency verification of the standard operation procedure for laboratory detection of immunoglobulin G oligoclonal bands in cerebrospinal fluid

Objective: To establish the standard operation procedure (SOP) for detection of oligoclonal band (OCB) in cerebrospinal fluid (CSF) and verify consistency by using this SOP in different laboratories. Methods: The SOP for detection of CSF-OCB fluid was successfully established by an expert feedback approach. Neuroimmunology laboratories in 3 representative Chinese three-tier research hospitals were selected for this study, and commercially available protein electrophoresis automation systems and detection SOP were set up. The quality control product was provided by the College of American Pathologists (CAP) and Sebiacompany were used for interior quality and compared to each other, respectively. Seventeen serum and CSF paired samples were tested and compared using the same SOP. Kappa test or Kendall W test were adopted to evaluate the inter-laboratory consistency among different hospitals. Results: The results of repeated testings in a single hospital suggested that the 2-and 4-fold dilution for CSF-OCB were reported as positive, while 64-and 128-fold dilution were reported as negative. Positive or negative inconsistencies were reported in 8-, 16-, and 32-fold dilution. After increasing the number of repetitions, the results showed that both 16-and 32-fold dilution were reported as negative, and 8-fold dilution exhibited negative results (2 positive results for 40 repetitions, coincidence rate=95%).The results of multi-center inter-laboratory quality assessment showed that the detection consistency rate among 3 hospitals was 100% (Kappa value =1). Conclusions: The SOP to detect CSF-OCB established in this study demonstrates a good repeatability and stability. Therefore,such SOP would be a good reference for diagnostic laboratories to detect CSF-OCB in China.