RBT
All tests were performed in duplicates. Reagents and quality control
samples were allowed to reach to room temperature before use. The RBT
(Biomerieux, France) was performed using a validated kit according to
the manufacturer’s instruction. The test was performed by thoroughly
mixing 30 μL of the test serum or controls with 30 μL of antigen
suspension on tear-drop ceramic plate, slowly rocked and incubated for 4
minutes. The presence of agglutination was observed immediately after
the incubation.