Relapsing fever laboratory findings

The presence of spirochetes in smears of peripheral blood, bone marrow, or cerebrospinal fluid in a symptomatic person is diagnostic of relapsing fever. The diagnosis of relapsing fever is confirmed by the identification of the borrelia in the patient’s blood under microscopy. Laboratory tests may also reveal mild anemia with normal to increased leukocyte count. Biochemistry may reveal Mildly increased serum bilirubin and hepatic aminotransferase level, increased urea nitrogen, creatinine, Elevated ESR. Slightly prolonged coagulation tests, PT and APTT, as well as proteinuria or hematuria, are also common

• The presence of spirochetes in smears of peripheral blood, bone marrow, or cerebrospinal fluid which stained with Giemsa, May-Grünwald Giemsa, Wright, Wright-Giemsa, Field’s, or Diff-Quick stains, or examined under dark-field while the patient is febrile, is diagnostic of relapsing fever. Although best visualized by darkfield microscopy, the organisms can also be detected by Wright-Giemsa or acridine orange-stained preparations.

• With subsequent febrile episodes, the number of circulating spirochetes decreases, making it harder to detect spirochetes on a peripheral blood smear. Even during the initial episode spirochetes will only be seen 70% of the time. ^[1]

• Antibody tests and PCR is available through public health laboratories and some private laboratories. Although there are false-positive and false-negative results.

More common:

• Normal to increased white blood cell count with a left shift towards immature cells
• Mild to moderate thrombocytopenia
• Mild anemia
• Elevated ESR

Less common:

• Mildly increased serum bilirubin and hepatic aminotransferase level
• increased urea nitrogen, creatinine
• Slightly prolonged coagulation tests, PT and APTT, as well as proteinuria or hematuria, are also common