How is it possible for the patient with three lines in a rapid test to be negative in the swab test? I have a scenario where three of my friends living together tested positive for IgG and IgM. This test brought them to be tested by swab. After three days, the swab test result came out and it is negative. Also, another friend of mine was tested by rapid test, came out to be positive in IgG and negative in IgM and two days after was tested via swab came out to be positive.