The best evidence for current infection is a significant change on two appropriately timed specimens where both tests are done in the same laboratory at the same time. However, low levels of IgM antibodies may occasionally persist for more than 12 months post-infection.
See Compliance Statement D
Statement D: This test was developed and its performance characteristics determined by ARUP Laboratories. The U.S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.