Schistosomiasis other diagnostic studies: Difference between revisions
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{{CMG}} ; {{AE}} {{ADG}} | {{CMG}} ; {{AE}} {{ADG}} | ||
==Overview== | ==Overview== | ||
There are | There are several other methods that can be used in the diagnosis of schistosomiasis such as [[Formalin|formalin-ethyl acetate sedimentation]], [[Urinalysis|urine testing]] for schistososme eggs, schistosomal antigen testing, [[Serology|serologic testing]], [[Biopsy|tissue biopsy]], [[PCR]] etc. | ||
==Other diagnostic studies== | ==Other diagnostic studies== | ||
'''Formalin-ethyl acetate sedimentation''' | '''Formalin-ethyl acetate sedimentation''' | ||
*Five grammes of stool is mixed, strained, diluted with | *Five grammes of stool is mixed, strained, diluted with [[normal saline]] solution and [[Centrifuge|centrifuged]]. | ||
*The sediment is collected and treated with formalin-ethyl acetate and subsequently used for slide preparation | *The [[sediment]] is collected and treated with [[Formalin|formalin-ethyl acetate]] and subsequently used for slide preparation. | ||
*A single formalin-ethyl acetate sedimentation test is not as sensitive for detection of low-intensity infection as multiple [[Kato-Katz technique|Kato-Katz]] smears | *A single [[Formalin|formalin-ethyl acetate]] sedimentation test is not as [[Sensitive Skin|sensitive]] for detection of low-intensity [[infection]] as multiple [[Kato-Katz technique|Kato-Katz]] smears. | ||
'''Urine testing for schistosome eggs''' | '''Urine testing for schistosome eggs''' | ||
*The classic method used for identification of ''[[Schistosoma haematobium|S.haematobium]]'' eggs is filter concentration of a [[urine]] sample collected over 4 hours (ending around noon) into a jug with formalin preservative | *The classic method used for identification of ''[[Schistosoma haematobium|S.haematobium]]'' eggs is filter concentration of a [[urine]] sample collected over 4 hours (ending around noon) into a jug with [[Formalin|formalin preservative]]. | ||
*10 mL of [[urine]] is filtered through a 12-μm pore membrane that traps the eggs, and the membrane surface then is examined under a microscope. | *10 mL of [[urine]] is filtered through a 12-μm pore membrane that traps the eggs, and the membrane surface then is examined under a [[microscope]]. | ||
*Standard microscopic urinalysis will not identify low-intensity Schistosoma infections. | *[[Urinalysis|Standard microscopic urinalysis]] will not identify low-intensity Schistosoma [[Infection|infections]]. | ||
*Each separate microscopic urinalysis has a sensitivity of 55% to 62% for detection of low-intensity infection; therefore, at least three different urine samples need to be evaluated to achieve diagnostic accuracy. | *Each separate [[Urinalysis|microscopic urinalysis]] has a [[Sensitivity (tests)|sensitivity]] of 55% to 62% for detection of low-intensity [[infection]]; therefore, at least three different [[Urine|urine samples]] need to be evaluated to achieve diagnostic accuracy. | ||
'''Schistosomal antigen testing (urine or serum)''' | '''Schistosomal antigen testing (urine or serum)''' | ||
*Urine sample is taken for measurement of circulating cathodic [[antigen]] released by schistosomes or serum sample for measurement of both circulating cathodic and anodic antigen.<ref name="pmid7814474">{{cite journal |vauthors=van Etten L, Folman CC, Eggelte TA, Kremsner PG, Deelder AM |title=Rapid diagnosis of schistosomiasis by antigen detection in urine with a reagent strip |journal=J. Clin. Microbiol. |volume=32 |issue=10 |pages=2404–6 |year=1994 |pmid=7814474 |pmc=264074 |doi= |url=}}</ref> | *[[Urine|Urine sample]] is taken for measurement of circulating cathodic [[antigen]] released by schistosomes or serum sample for measurement of both circulating [[Cathodic protection|cathodic]] and [[Anodic oxidation|anodic]] [[antigen]].<ref name="pmid7814474">{{cite journal |vauthors=van Etten L, Folman CC, Eggelte TA, Kremsner PG, Deelder AM |title=Rapid diagnosis of schistosomiasis by antigen detection in urine with a reagent strip |journal=J. Clin. Microbiol. |volume=32 |issue=10 |pages=2404–6 |year=1994 |pmid=7814474 |pmc=264074 |doi= |url=}}</ref> | ||
*Identifies active infection rather than past infection | *Identifies active [[infection]] rather than past [[infection]]. | ||
*May not be sufficiently sensitive for detection of low-intensity infection | *May not be sufficiently sensitive for detection of low-intensity infection. | ||
'''Serologic testing''' | '''Serologic testing''' | ||
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*More useful for evaluating recent travelers than immigrants, as it is not possible to distinguish between active infection and past infection. | *More useful for evaluating recent travelers than immigrants, as it is not possible to distinguish between active infection and past infection. | ||
*Due to the long life of schistosomes, positive test results cannot be discounted simply because exposure was historically distant. | *Due to the long life of schistosomes, positive test results cannot be discounted simply because exposure was historically distant. | ||
*Sensitivity is highest when the assay is targeted to the suspected species (''[[Schistosoma mansoni|S.mansoni]]'', ''[[Schistosoma japonicum|S.japonicum]], or [[Schistosoma haematobium|S.haematobium]]'') | *[[Sensitivity (tests)|Sensitivity]] is highest when the assay is targeted to the suspected species (''[[Schistosoma mansoni|S.mansoni]]'', ''[[Schistosoma japonicum|S.japonicum]], or [[Schistosoma haematobium|S.haematobium]]'') | ||
'''Biopsy of tissue''' | '''Biopsy of tissue''' | ||
*A biopsy specimen is obtained from the rectum during [[anoscopy]], [[Genital|genital tissues]], or the [[urinary bladder]] wall during [[cystoscopy]] and then crushed and examined under a microscope | *A [[biopsy]] specimen is obtained from the [[rectum]] during [[anoscopy]], [[Genital|genital tissues]], or the [[urinary bladder]] wall during [[cystoscopy]] and then crushed and examined under a [[microscope]] | ||
*[[Schistosoma mansoni|''S.mansoni'']] and ''[[Schistosoma japonicum|S.japonicum]]'' eggs can be identified in crushed random [[Biopsy|rectal biopsy]] specimens. | *[[Schistosoma mansoni|''S.mansoni'']] and ''[[Schistosoma japonicum|S.japonicum]]'' eggs can be identified in crushed random [[Biopsy|rectal biopsy]] specimens. | ||
*[[Schistosoma haematobium|''S.haematobium'']] eggs can be identified in crushed biopsy specimens from genital tissues or the [[urinary bladder]] wall | *[[Schistosoma haematobium|''S.haematobium'']] eggs can be identified in crushed biopsy specimens from [[Genital area|genital tissues]] or the [[urinary bladder]] wall. | ||
*[[Sensitivity]] of microscopic analysis of six crushed rectal biopsies is similar to that of two [[Kato-Katz thick smear|Kato-Katz thick smears]]. | *[[Sensitivity]] of microscopic analysis of six crushed rectal biopsies is similar to that of two [[Kato-Katz thick smear|Kato-Katz thick smears]]. | ||
*[[Liver]] biopsy is notoriously insensitive for diagnosis of schistosomiasis; a negative liver biopsy result does not exclude infection | *[[Liver]] biopsy is notoriously insensitive for diagnosis of schistosomiasis; a negative liver biopsy result does not exclude infection. | ||
*Standard sectioned intestinal biopsies are not sufficiently sensitive for diagnosis of intestinal schistosomiasis. | *Standard sectioned [[intestinal]] [[biopsies]] are not sufficiently sensitive for diagnosis of [[intestinal]] [[schistosomiasis]]. | ||
'''PCR to detect schistosomal DNA''' | '''PCR to detect schistosomal DNA''' | ||
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'''Other laboratory tests''' | '''Other laboratory tests''' | ||
Other diagnostic tests that are helpful in diagnosis of schistosomiasis include: | Other diagnostic tests that are helpful in diagnosis of schistosomiasis include: | ||
*Urinalysis, including dipstick testing and microscopic analysis for [[leukocytes]], [[erythrocytes]], and [[Urinary casts|casts]]. | *[[Urinalysis]], including [[Dipsticks|dipstick]] testing and [[Microscope image processing|microscopic analysis]] for [[leukocytes]], [[erythrocytes]], and [[Urinary casts|casts]]. | ||
**If obstruction is causing a [[urinary tract infection]], [[leukocyte esterase]] or [[nitrites]] may be present. | **If [[obstruction]] is causing a [[urinary tract infection]], [[leukocyte esterase]] or [[nitrites]] may be present. | ||
**[[Erythrocytes]] are seen in the urine of patients with glomerulonephritis. | **[[Erythrocytes]] are seen in the [[urine]] of patients with [[glomerulonephritis]]. | ||
**Urinary casts, which are aggregates of [[protein]], [[blood cells]], tubular epithelial cell constituents, or all three, develop secondary to urinary stasis in renal tubules and significant [[proteinuria]]. | **[[Urinary casts]], which are aggregates of [[protein]], [[blood cells]], [[Epithelial cell|tubular epithelial cell]] constituents, or all three, develop secondary to [[Urinary System|urinary stasis]] in [[renal tubules]] and significant [[proteinuria]]. | ||
*Measurement of blood urea nitrogen ([[Blood urea nitrogen|BUN]]) and [[serum creatinine]] to test renal function. | *Measurement of [[blood urea nitrogen]] ([[Blood urea nitrogen|BUN]]) and [[serum creatinine]] to test [[renal function]]. | ||
*[[Liver function tests]] | *[[Liver function tests]] | ||
**[[Aspartate transaminase|AST]] and [[Alanine transaminase|ALT]] levels usually remain normal, even in patients with hepatosplenic disease. | **[[Aspartate transaminase|AST]] and [[Alanine transaminase|ALT]] levels usually remain normal, even in patients with hepatosplenic [[disease]]. | ||
**[[Albumin]] levels may be low due to [[malnutrition]] or nephrotic forms of schistosomiasis. | **[[Albumin]] levels may be low due to [[malnutrition]] or [[Nephrotic syndrome|nephrotic]] forms of schistosomiasis. | ||
*[[Complete blood count|Complete blood count (]]CBC) | *[[Complete blood count|Complete blood count (]]CBC) | ||
**[[Anemia]] may be seen in patients with chronic blood loss due to intestinal or urinary schistosomiasis and in those with glomerular disease. | **[[Anemia]] may be seen in patients with chronic blood loss due to intestinal or urinary schistosomiasis and in those with glomerular disease. | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Overview
There are several other methods that can be used in the diagnosis of schistosomiasis such as formalin-ethyl acetate sedimentation, urine testing for schistososme eggs, schistosomal antigen testing, serologic testing, tissue biopsy, PCR etc.
Other diagnostic studies
Formalin-ethyl acetate sedimentation
- Five grammes of stool is mixed, strained, diluted with normal saline solution and centrifuged.
- The sediment is collected and treated with formalin-ethyl acetate and subsequently used for slide preparation.
- A single formalin-ethyl acetate sedimentation test is not as sensitive for detection of low-intensity infection as multiple Kato-Katz smears.
Urine testing for schistosome eggs
- The classic method used for identification of S.haematobium eggs is filter concentration of a urine sample collected over 4 hours (ending around noon) into a jug with formalin preservative.
- 10 mL of urine is filtered through a 12-μm pore membrane that traps the eggs, and the membrane surface then is examined under a microscope.
- Standard microscopic urinalysis will not identify low-intensity Schistosoma infections.
- Each separate microscopic urinalysis has a sensitivity of 55% to 62% for detection of low-intensity infection; therefore, at least three different urine samples need to be evaluated to achieve diagnostic accuracy.
Schistosomal antigen testing (urine or serum)
- Urine sample is taken for measurement of circulating cathodic antigen released by schistosomes or serum sample for measurement of both circulating cathodic and anodic antigen.[1]
- Identifies active infection rather than past infection.
- May not be sufficiently sensitive for detection of low-intensity infection.
Serologic testing
- Serologic testing help in detection of Schistosoma-specific antibodies in serum. These tests include:
- Enzyme-linked immunosorbent assay
- Indirect hemagglutination assay
- Indirect immunofluorescent antibody testing
- More useful for evaluating recent travelers than immigrants, as it is not possible to distinguish between active infection and past infection.
- Due to the long life of schistosomes, positive test results cannot be discounted simply because exposure was historically distant.
- Sensitivity is highest when the assay is targeted to the suspected species (S.mansoni, S.japonicum, or S.haematobium)
Biopsy of tissue
- A biopsy specimen is obtained from the rectum during anoscopy, genital tissues, or the urinary bladder wall during cystoscopy and then crushed and examined under a microscope
- S.mansoni and S.japonicum eggs can be identified in crushed random rectal biopsy specimens.
- S.haematobium eggs can be identified in crushed biopsy specimens from genital tissues or the urinary bladder wall.
- Sensitivity of microscopic analysis of six crushed rectal biopsies is similar to that of two Kato-Katz thick smears.
- Liver biopsy is notoriously insensitive for diagnosis of schistosomiasis; a negative liver biopsy result does not exclude infection.
- Standard sectioned intestinal biopsies are not sufficiently sensitive for diagnosis of intestinal schistosomiasis.
PCR to detect schistosomal DNA
- Gene amplification technique used to detect schistosomal DNA.
Other laboratory tests Other diagnostic tests that are helpful in diagnosis of schistosomiasis include:
- Urinalysis, including dipstick testing and microscopic analysis for leukocytes, erythrocytes, and casts.
- If obstruction is causing a urinary tract infection, leukocyte esterase or nitrites may be present.
- Erythrocytes are seen in the urine of patients with glomerulonephritis.
- Urinary casts, which are aggregates of protein, blood cells, tubular epithelial cell constituents, or all three, develop secondary to urinary stasis in renal tubules and significant proteinuria.
- Measurement of blood urea nitrogen (BUN) and serum creatinine to test renal function.
- Liver function tests
- Complete blood count (CBC)
- Anemia may be seen in patients with chronic blood loss due to intestinal or urinary schistosomiasis and in those with glomerular disease.
- Eosinophilia may be prominent early in the disease course but may be minimal in patients with longstanding disease.
