Schistosomiasis laboratory findings: Difference between revisions

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{{Schistosomiasis}}
{{Schistosomiasis}}
{{CMG}}
{{CMG}} ; {{AE}} {{ADG}}


==Overview==
==Overview==
Microscopic identification of eggs in [[feces|stool]] or [[urine]] is the most practical method for diagnosis. The stool exam is the more common of the two. For the measurement of eggs in the feces of presenting patients the scientific unit used is [[epg]] or [[eggs per gram]].  Stool examination should be performed when infection with ''S. mansoni'' or ''S. japonicum'' is suspected, and urine examination should be performed if ''S. haematobium'' is suspected.
Methods for diagnosing schistosomiasis include visualization of Schistosoma eggs in [[stool]], [[urine]], and crushed [[Biopsy|biopsy tissues]]. [[Serological testing|serologic assays]] and urinary antigen testing have also been used. Laboratory findings consistent with the diagnosis of schistosomiasis include detection of circulating [[antibodies]] to schistosomes and schistosomal [[antigen]] in [[serum]].


==Laboratory Findings==
==Laboratory Findings==
Visualization of schistosoma eggs in stool, urine, and crushed biopsy tissues is diagnostic of schistosomiasis. Laboratory findings consistent with the diagnosis of schistosomiasis include detection of circulating antibodies to schistosomes and schistosomal antigen in serum. Diagnostic tests for schistosomiasis include the following:<ref name="pmid21633040">{{cite journal |vauthors=Ibironke OA, Phillips AE, Garba A, Lamine SM, Shiff C |title=Diagnosis of Schistosoma haematobium by detection of specific DNA fragments from filtered urine samples |journal=Am. J. Trop. Med. Hyg. |volume=84 |issue=6 |pages=998–1001 |year=2011 |pmid=21633040 |pmc=3110375 |doi=10.4269/ajtmh.2011.10-0691 |url=}}</ref>
Visualization of Schistosoma eggs in [[stool]], [[urine]], and [[Biopsy|crushed biopsy tissues]] is diagnostic of schistosomiasis. Laboratory findings consistent with the diagnosis of schistosomiasis include detection of circulating [[antibodies]] to schistosomes and schistosomal [[antigen]] in [[serum]]. Diagnostic tests for schistosomiasis include the following:<ref name="pmid21633040">{{cite journal |vauthors=Ibironke OA, Phillips AE, Garba A, Lamine SM, Shiff C |title=Diagnosis of Schistosoma haematobium by detection of specific DNA fragments from filtered urine samples |journal=Am. J. Trop. Med. Hyg. |volume=84 |issue=6 |pages=998–1001 |year=2011 |pmid=21633040 |pmc=3110375 |doi=10.4269/ajtmh.2011.10-0691 |url=}}</ref><ref name="urlCDC - DPDx - Schistosomiasis Infection - Laboratory Diagnosis">{{cite web |url=https://www.cdc.gov/dpdx/schistosomiasis/dx.html |title=CDC - DPDx - Schistosomiasis Infection - Laboratory Diagnosis |format= |work= |accessdate=}}</ref><ref name="pmid26224883">{{cite journal |vauthors=Weerakoon KG, Gobert GN, Cai P, McManus DP |title=Advances in the Diagnosis of Human Schistosomiasis |journal=Clin. Microbiol. Rev. |volume=28 |issue=4 |pages=939–67 |year=2015 |pmid=26224883 |pmc=4548261 |doi=10.1128/CMR.00137-14 |url=}}</ref>
*Microscopic examination of stool
*[[Microscopic examination]] of [[stool]]
*Urine testing for schistosome eggs
*[[Urinalysis|Urine testing]] for schistosome eggs
*Serologic testing
*[[Serological testing|Serologic testing]]
*Schistosomal antigen testing (urine or serum)
*Schistosomal [[antigen]] testing ([[urine]] or [[serum]])
*Microscopic examination of tissue
*[[Microscopic examination]] of [[Tissue (biology)|tissue]]
*PCR to detect schistosomal DNA
*[[PCR]] to detect schistosomal [[DNA]]
===Microscopic examination of stool===
===Microscopic examination of stool===
*The classic and most commonly used method for identification of schistosome eggs in stool is a modified Kato-Katz thick smear.<ref name="pmid19772859">{{cite journal |vauthors=Tarafder MR, Carabin H, Joseph L, Balolong E, Olveda R, McGarvey ST |title=Estimating the sensitivity and specificity of Kato-Katz stool examination technique for detection of hookworms, Ascaris lumbricoides and Trichuris trichiura infections in humans in the absence of a 'gold standard' |journal=Int. J. Parasitol. |volume=40 |issue=4 |pages=399–404 |year=2010 |pmid=19772859 |pmc=2829363 |doi=10.1016/j.ijpara.2009.09.003 |url=}}</ref>
*The classic and most commonly used method for identification of schistosome eggs in [[stool]] is a modified [[Kato-Katz thick smear]].<ref name="pmid19772859">{{cite journal |vauthors=Tarafder MR, Carabin H, Joseph L, Balolong E, Olveda R, McGarvey ST |title=Estimating the sensitivity and specificity of Kato-Katz stool examination technique for detection of hookworms, Ascaris lumbricoides and Trichuris trichiura infections in humans in the absence of a 'gold standard' |journal=Int. J. Parasitol. |volume=40 |issue=4 |pages=399–404 |year=2010 |pmid=19772859 |pmc=2829363 |doi=10.1016/j.ijpara.2009.09.003 |url=}}</ref>
*Testing should be done on formed stool, as schistosomiasis typically does not cause diarrhea.
*Testing should be done on formed [[stool]], as schistosomiasis typically does not cause [[diarrhea]].
*Several areas of a stool specimen should be evaluated independently, as eggs are not deposited uniformly throughout. In addition, eggs are not deposited uniformly throughout the day, and, thus, three different stool specimens should be evaluated.
*Several areas of a [[Stool examination|stool specimen]] should be evaluated independently, as eggs are not deposited uniformly throughout. In addition, eggs are not deposited uniformly throughout the day, and, thus, three different [[Stool examination|stool specimens]] should be evaluated.
*One to 99 eggs/g is suggestive of mild infection, 100 to 299 eggs/g indicate moderate infection, and more than 300 eggs/g are indicative of high-intensity infection.
*One to 99 eggs/g is suggestive of mild infection, 100 to 299 eggs/g indicate moderate infection, and more than 300 eggs/g are indicative of high-intensity infection.
*Kato Katz smears are not sufficiently sensitive for detection of low-intensity infections. Other techniques may be superior but often are unavailable or more difficult to use.  
*[[Kato-Katz thick smear|Kato Katz smears]] are not sufficiently [[Sensitive Skin|sensitive]] for detection of low-intensity [[infections]]. Other techniques may be superior but often are unavailable or more difficult to use.  
{{#ev:youtube|WpcZejHa_jM}}
{{#ev:youtube|WpcZejHa_jM}}
[[Image:Schistosoma japonicum (3) histopathology.JPG|thumb|center|''S. japonicum'' eggs in hepatic portal tract.]]


===Other Methods===
'''Other laboratory tests'''
'''Formalin-ethyl acetate sedimentation'''
*In formalin-ethyl acetate sedimentation 2 to 5 g of stool is mixed, strained, diluted with normal saline solution.
*It is then 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===
Other diagnostic tests that are helpful in diagnosis of schistosomiasis include:
*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
*[[Urinalysis]], including [[Dipsticks|dipstick]] testing and [[Microscope image processing|microscopic analysis]] for [[leukocytes]], [[erythrocytes]], and [[Urinary casts|casts]].
*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.
*Measurement of [[blood urea nitrogen]] ([[Blood urea nitrogen|BUN]]) and [[serum creatinine]] to test [[renal function]].
*Standard microscopic urinalysis will not identify low-intensity Schistosoma infections.
*[[Liver function tests]]
*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.
*[[Complete blood count|Complete blood count (]]CBC)
===Schistosomal antigen testing (urine or serum)===
**[[Anemia]]
*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>
**[[Eosinophilia]]
*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.
**AST and ALT levels usually remain normal, even in patients with hepatosplenic disease
**Albumin levels may be low due to malnutrition or nephrotic forms of schistosomiasis
*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.
[[Image:Schistosoma bladder histopathology.jpeg|thumb|center|Photomicrography of bladder in ''S. hematobium'' infection, showing clusters of the parasite eggs with intense eosinophilia, Source: CDC]]
[[Image:Schistosoma bladder histopathology.jpeg|thumb|center|Photomicrography of bladder in ''S. hematobium'' infection, showing clusters of the parasite eggs with intense eosinophilia, Source: CDC]]


==References==
==References==
{{Reflist|2}}
{{Reflist|2}}
[[Category:Disease]]
[[Category:Water-borne diseases]]
[[Category:Parasitic diseases]]
[[Category:Zoonoses]]
[[Category:Tropical disease]]
[[Category:Hepatology]]
[[Category:Neglected diseases]]
[[Category:Infectious disease]]

Latest revision as of 12:46, 23 August 2017

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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

Methods for diagnosing schistosomiasis include visualization of Schistosoma eggs in stool, urine, and crushed biopsy tissues. serologic assays and urinary antigen testing have also been used. Laboratory findings consistent with the diagnosis of schistosomiasis include detection of circulating antibodies to schistosomes and schistosomal antigen in serum.

Laboratory Findings

Visualization of Schistosoma eggs in stool, urine, and crushed biopsy tissues is diagnostic of schistosomiasis. Laboratory findings consistent with the diagnosis of schistosomiasis include detection of circulating antibodies to schistosomes and schistosomal antigen in serum. Diagnostic tests for schistosomiasis include the following:[1][2][3]

Microscopic examination of stool

  • The classic and most commonly used method for identification of schistosome eggs in stool is a modified Kato-Katz thick smear.[4]
  • Testing should be done on formed stool, as schistosomiasis typically does not cause diarrhea.
  • Several areas of a stool specimen should be evaluated independently, as eggs are not deposited uniformly throughout. In addition, eggs are not deposited uniformly throughout the day, and, thus, three different stool specimens should be evaluated.
  • One to 99 eggs/g is suggestive of mild infection, 100 to 299 eggs/g indicate moderate infection, and more than 300 eggs/g are indicative of high-intensity infection.
  • Kato Katz smears are not sufficiently sensitive for detection of low-intensity infections. Other techniques may be superior but often are unavailable or more difficult to use.

{{#ev:youtube|WpcZejHa_jM}}

Other laboratory tests

Other diagnostic tests that are helpful in diagnosis of schistosomiasis include:

Photomicrography of bladder in S. hematobium infection, showing clusters of the parasite eggs with intense eosinophilia, Source: CDC

References

  1. Ibironke OA, Phillips AE, Garba A, Lamine SM, Shiff C (2011). "Diagnosis of Schistosoma haematobium by detection of specific DNA fragments from filtered urine samples". Am. J. Trop. Med. Hyg. 84 (6): 998–1001. doi:10.4269/ajtmh.2011.10-0691. PMC 3110375. PMID 21633040.
  2. "CDC - DPDx - Schistosomiasis Infection - Laboratory Diagnosis".
  3. Weerakoon KG, Gobert GN, Cai P, McManus DP (2015). "Advances in the Diagnosis of Human Schistosomiasis". Clin. Microbiol. Rev. 28 (4): 939–67. doi:10.1128/CMR.00137-14. PMC 4548261. PMID 26224883.
  4. Tarafder MR, Carabin H, Joseph L, Balolong E, Olveda R, McGarvey ST (2010). "Estimating the sensitivity and specificity of Kato-Katz stool examination technique for detection of hookworms, Ascaris lumbricoides and Trichuris trichiura infections in humans in the absence of a 'gold standard'". Int. J. Parasitol. 40 (4): 399–404. doi:10.1016/j.ijpara.2009.09.003. PMC 2829363. PMID 19772859.