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{{Relapsing fever}}
{{Relapsing fever}}
{{CMG}}
{{CMG}}
==Overview==
The presence of [[spirochetes]] in [[Peripheral blood smear|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|urea nitrogen]], [[creatinine]], Elevated [[ESR]].
Slightly prolonged [[coagulation|coagulation tests]], [[PT]] and [[APTT]], as well as [[proteinuria]] or [[hematuria]], are also common


==Laboratory Findings==  
==Laboratory Findings==  
[[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]]
*The definitive diagnosis of TBRF is based on the observation of Borrelia spirochetes in smears of peripheral [[blood]], [[bone marrow]], or [[cerebrospinal fluid]] in a symptomatic person.  Although best visualized by dark field microscopy, the organisms can also be detected by Wright-Giemsa or acridine orange-stained preparations.


*The organisms are best detected in blood obtained while a person is [[febrile]]. 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.  
===Microscopic Diagnosis===
*The presence of [[spirochetes]] in smears of peripheral [[blood]], [[bone marrow]], or [[cerebrospinal fluid]]  which stained with [[Giemsa]], May-Grünwald Giemsa, [[Wright's stain|Wright]], Wright-Giemsa, [[Field's stain|Field's]], or Diff-Quick stains, or examined under [[Darkfield microscope|dark-field]] while the patient is [[febrile]], is diagnostic of [[relapsing fever]]. Although best visualized by [[Darkfield microscope|darkfield microscopy]], the [[organisms]] can also be detected by Wright-Giemsa or [[Acridine orange|acridine orange-stained]] preparations.


Blood samples obtained before [[antibiotic]] treatment can be cultured using BSK medium or by inoculating immature miceThe spirochete will usually be evident within 24 hours if the blood was drawn during a febrile episode.  
*With subsequent [[febrile]] episodes, the number of circulating [[spirochetes]] decreases, making it harder to detect [[spirochetes]] on a peripheral blood smearEven 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>


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 TBRF, 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.  Serologic testing for TBRF is not standardized and results may vary by lab.  Patients with TBRF may have false-positive tests for Lyme disease because of the similarity of proteins between the two organisms.
===Molecular Diagnosis and serology===
*Antibody tests and [[PCR]] is available through public health laboratories and some private laboratories. Although there are [[false-positive]] and [[false-negative]] results.


Incidental laboratory findings include normal to increased white blood cell count with a left shift towards immature cells, a mildly increased serum [[bilirubin]] level, mild to moderate [[thrombocytopenia]] (low platelet count), elevated [[ESR]] and slightly prolonged coagulation tests, [[PT]] and [[APTT]].
===Other laboratory findings===
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|urea nitrogen]], [[creatinine]]
*Slightly prolonged [[coagulation|coagulation tests]], [[PT]] and [[APTT]], as well as [[proteinuria]] or [[hematuria]], are also common


==References==
==References==
{{Reflist|2}}
{{Reflist|2}}


 
[[Category:Needs overview]]
[[Category:Bacterial diseases]]
[[Category:Bacterial diseases]]
[[Category:Zoonoses]]
[[Category:Zoonoses]]
[[Category:Infectious diseases]]
[[Category:Infectious diseases]]

Latest revision as of 01:20, 25 September 2020

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

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

Laboratory Findings

Borrelia spirochetes
Peripheral blood smear from Schwan, Policastro et al 2003

Microscopic Diagnosis

  • 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]

Molecular Diagnosis and serology

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

Other laboratory findings

More common:

Less common:

References

  1. 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.