Relapsing fever laboratory findings: Difference between revisions
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[[Image:Borrelia spirochetes.jpg|right|thumb|Borrelia spirochetes]] | [[Image:Borrelia spirochetes.jpg|right|thumb|Borrelia spirochetes]] | ||
[[Image:Peripheral blood smear from Schwan, Policastro et al.jpg|right|thumb|Peripheral blood smear from Schwan, Policastro et al 2003]] | [[Image:Peripheral blood smear from Schwan, Policastro et al.jpg|right|thumb|Peripheral blood smear from Schwan, Policastro et al 2003]] | ||
* | |||
'''Blood smear:''' | |||
*The presence of spirochetes in smears of peripheral [[blood]], [[bone marrow]], or [[cerebrospinal fluid]] in a symptomatic person 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. <ref name="pmid26618151">{{cite journal |vauthors=Fotso Fotso A, Drancourt M |title=Laboratory Diagnosis of Tick-Borne African Relapsing Fevers: Latest Developments |journal=Front Public Health |volume=3 |issue= |pages=254 |date=2015 |pmid=26618151 |pmc=4641162 |doi=10.3389/fpubh.2015.00254 |url=}}</ref> | *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. <ref name="pmid26618151">{{cite journal |vauthors=Fotso Fotso A, Drancourt M |title=Laboratory Diagnosis of Tick-Borne African Relapsing Fevers: Latest Developments |journal=Front Public Health |volume=3 |issue= |pages=254 |date=2015 |pmid=26618151 |pmc=4641162 |doi=10.3389/fpubh.2015.00254 |url=}}</ref> | ||
'''Blood culture''' | |||
Blood samples obtained before [[antibiotic]] treatment can be cultured using BSK medium or by inoculating immature mice. The spirochete will usually be evident within 24 hours if the blood was drawn during a febrile episode. | Blood samples obtained before [[antibiotic]] treatment can be cultured using BSK medium or by inoculating immature mice. The spirochete will usually be evident within 24 hours if the blood was drawn during a febrile episode. | ||
Although not valuable for making an immediate diagnosis, serologic testing is available through public health laboratories and some private laboratories. Acute serum should be taken within 7 days of symptom onset and convalescent serum should be taken at least 21 days after symptoms start. Early [[antibiotic]] treatment may blunt the [[antibody]] response and the antibody levels may wane quickly during the months after exposure. To confirm the diagnosis of | '''Serologic tests''' | ||
Although not valuable for making an immediate diagnosis, serologic testing is available through public health laboratories and some private laboratories. Acute serum should be taken within 7 days of symptom onset and convalescent serum should be taken at least 21 days after symptoms start. Early [[antibiotic]] treatment may blunt the [[antibody]] response and the antibody levels may wane quickly during the months after exposure. To confirm the diagnosis of RF, Borrelia specific antibody titers should be increased between acute and convalescent serum samples and convalescent serum antibody levels should be at least two standard deviations above pooled negative controls. Patients with TBRF may have false-positive tests for Lyme disease because of the similarity of proteins between the two organisms. | |||
'''Other laboratory findings include: | |||
''' | |||
More common: | |||
*Normal to increased white blood cell count with a left shift towards immature cells | *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 | *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 | *Slightly prolonged coagulation tests, [[PT]] and [[APTT]], as well as proteinuria or hematuria, are also common | ||
Revision as of 20:23, 9 August 2020
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Laboratory Findings
Blood smear:
- The presence of spirochetes in smears of peripheral blood, bone marrow, or cerebrospinal fluid in a symptomatic person 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]
Blood culture
Blood samples obtained before antibiotic treatment can be cultured using BSK medium or by inoculating immature mice. The spirochete will usually be evident within 24 hours if the blood was drawn during a febrile episode.
Serologic tests
Although not valuable for making an immediate diagnosis, serologic testing is available through public health laboratories and some private laboratories. Acute serum should be taken within 7 days of symptom onset and convalescent serum should be taken at least 21 days after symptoms start. Early antibiotic treatment may blunt the antibody response and the antibody levels may wane quickly during the months after exposure. To confirm the diagnosis of RF, Borrelia specific antibody titers should be increased between acute and convalescent serum samples and convalescent serum antibody levels should be at least two standard deviations above pooled negative controls. Patients with TBRF may have false-positive tests for Lyme disease because of the similarity of proteins between the two organisms.
Other laboratory findings include:
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
References
- ↑ Fotso Fotso A, Drancourt M (2015). "Laboratory Diagnosis of Tick-Borne African Relapsing Fevers: Latest Developments". Front Public Health. 3: 254. doi:10.3389/fpubh.2015.00254. PMC 4641162. PMID 26618151.