There's no definitive accredited lab check as far as I know. At least here in Germany the official serologic tests for late stage Lyme can come back negative for years until the disease really progresses badly - even cerebrospinal fluid results may be normal despite neurological symptoms. My specialist uses elispot lab tests for Borrelia b. OspA, antigen and LFA-1 markers.

Other practitioners use westernblot lab results and differential diagnosis.