Q fever laboratory tests: Difference between revisions
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{{Q fever}} | {{Q fever}} | ||
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==Overview== | |||
Laboratory findings consistent with the diagnosis of Q fever include [[Serology|positive serology]] for [[antibodies]] (especially [[Immunofluorescence|indirect immunofluorescence (IIF),]] positive [[PCR]], and [[Liver enzymes|elevated liver enzymes]]. | |||
== | ==Laboratory tests== | ||
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===Serologic testing for Q fever=== | |||
*[[Immunofluorescence|Indirect immunofluorescence (IIF)]] is the method of choice for [[antibody]] detection and is preferred over [[ELISA]] and [[complement fixation]].<ref name="urlDiagnosis of Q Fever">{{cite web |url=http://jcm.asm.org/content/36/7/1823.short |title=Diagnosis of Q Fever |format= |work= |accessdate=}}</ref><ref name="pmid7496944">{{cite journal |vauthors=Dupont HT, Thirion X, Raoult D |title=Q fever serology: cutoff determination for microimmunofluorescence |journal=Clin. Diagn. Lab. Immunol. |volume=1 |issue=2 |pages=189–96 |year=1994 |pmid=7496944 |pmc=368226 |doi= |url=}}</ref> | |||
*[[Antibodies]] start to be detected after 7-14 days of infection, with most patients testing positive by the third week. | |||
*[[Antibodies|Anti phase II antibodies]] are tested first. If positive, [[Antibodies|anti phase I antibodies]] are tested. | |||
*After acute infection, [[Serology|serologic]] follow-up for serum [[Antibodies|anti phase I IgG antibodies]]. The test is done twice every 3 months for 2 years. If it's positive, a [[Transesophageal echo cardiography|transesophageal echo]] should be done to rule out [[endocarditis]].<ref name="pmid6622891">{{cite journal |vauthors=Derrick EH |title="Q" fever, a new fever entity: clinical features, diagnosis and laboratory investigation |journal=Rev. Infect. Dis. |volume=5 |issue=4 |pages=790–800 |year=1983 |pmid=6622891 |doi= |url=}}</ref> | |||
*All [[Serology|serologic]] test results should be used in the context of clinical data because false positive test results are seen in many other diseases (e.g. [[leptospirosis]]). | |||
===Polymerase chain reaction (PCR)=== | |||
*[[PCR]] can be used to detect ''[[Coxiella burnetii|C.]] [[Coxiella burnetii|burnetii]]'' [[DNA]] in [[Culture medium|cultures]] and clinical samples. | |||
*[[PCR]] is positive in the first week of infection, thus it can be used to diagnose Q fever in patients who are [[Serology|serologically]] negative in the early stages of the disease.<ref name="pmid10515901">{{cite journal |vauthors=Maurin M, Raoult D |title=Q fever |journal=Clin. Microbiol. Rev. |volume=12 |issue=4 |pages=518–53 |year=1999 |pmid=10515901 |pmc=88923 |doi= |url=}}</ref> | |||
*Quantitative [[PCR]] also can be used in patients whose [[Immunoglobulin G|anti phase II IgG antibodies]] are persistently positive in order to detect [[chronic]] Q fever. | |||
===Cultures=== | |||
*''[[Coxiella burnetii|C.]] [[Coxiella burnetii|burnetii]]'' doesn’t grow on ordinary [[blood cultures]] but can be cultivated on special media as embryonated eggs or [[cell culture]]. | |||
*''[[Coxiella burnetii|C.]] [[Coxiella burnetii|burnetii]]'' is extremely infectious and samples should be handled with caution. | |||
===Liver function tests=== | |||
*A two-to-three fold increase in [[AST]] and [[ALT]] is seen in most patients. | |||
==References== | ==References== | ||
{{Reflist|2}} | {{Reflist|2}} | ||
[[Category: | [[Category:Emergency mdicine]] | ||
[[Category:Disease]] | |||
[[Category:Up-To-Date]] | |||
[[Category:Infectious disease]] | [[Category:Infectious disease]] | ||
[[Category: | [[Category:Gastroenterology]] | ||
[[Category:Hepatology]] | |||
[[ | [[Category:Pulmonology]] | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Ahmed Younes M.B.B.CH [2]
Overview
Laboratory findings consistent with the diagnosis of Q fever include positive serology for antibodies (especially indirect immunofluorescence (IIF), positive PCR, and elevated liver enzymes.
Laboratory tests
Serologic testing for Q fever
- Indirect immunofluorescence (IIF) is the method of choice for antibody detection and is preferred over ELISA and complement fixation.[1][2]
- Antibodies start to be detected after 7-14 days of infection, with most patients testing positive by the third week.
- Anti phase II antibodies are tested first. If positive, anti phase I antibodies are tested.
- After acute infection, serologic follow-up for serum anti phase I IgG antibodies. The test is done twice every 3 months for 2 years. If it's positive, a transesophageal echo should be done to rule out endocarditis.[3]
- All serologic test results should be used in the context of clinical data because false positive test results are seen in many other diseases (e.g. leptospirosis).
Polymerase chain reaction (PCR)
- PCR can be used to detect C. burnetii DNA in cultures and clinical samples.
- PCR is positive in the first week of infection, thus it can be used to diagnose Q fever in patients who are serologically negative in the early stages of the disease.[4]
- Quantitative PCR also can be used in patients whose anti phase II IgG antibodies are persistently positive in order to detect chronic Q fever.
Cultures
- C. burnetii doesn’t grow on ordinary blood cultures but can be cultivated on special media as embryonated eggs or cell culture.
- C. burnetii is extremely infectious and samples should be handled with caution.
Liver function tests
References
- ↑ "Diagnosis of Q Fever".
- ↑ Dupont HT, Thirion X, Raoult D (1994). "Q fever serology: cutoff determination for microimmunofluorescence". Clin. Diagn. Lab. Immunol. 1 (2): 189–96. PMC 368226. PMID 7496944.
- ↑ Derrick EH (1983). ""Q" fever, a new fever entity: clinical features, diagnosis and laboratory investigation". Rev. Infect. Dis. 5 (4): 790–800. PMID 6622891.
- ↑ Maurin M, Raoult D (1999). "Q fever". Clin. Microbiol. Rev. 12 (4): 518–53. PMC 88923. PMID 10515901.