Schistosomiasis laboratory findings: Difference between revisions

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[[Image:Schistosoma japonicum (3) histopathology.JPG|thumb|center|''S. japonicum'' eggs in hepatic portal tract. Source:By User:KGH - Own work, CC BY-SA 3.0, <nowiki>https://commons.wikimedia.org/w/index.php?curid=510508</nowiki>]]
[[Image:Schistosoma japonicum (3) histopathology.JPG|thumb|center|''S. japonicum'' eggs in hepatic portal tract. Source:By User:KGH - Own work, CC BY-SA 3.0, <nowiki>https://commons.wikimedia.org/w/index.php?curid=510508</nowiki>]]


===Other Methods===
'''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 technique|Kato-Katz]] smears
===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
*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.<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
*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 antiglobulin test|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 (''[[Schistosoma mansoni|S.mansoni]]'', ''[[Schistosoma japonicum|S.japonicum]], or [[Schistosoma haematobium|S.haematobium]]'')
===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
*[[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
*[[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
*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 [[Urinary casts|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 ([[Blood urea nitrogen|BUN]]) and [[serum creatinine]] to test renal function.
*[[Liver function tests]]
**[[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.
*[[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.
**[[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]]


==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]]

Revision as of 11:54, 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}}

S. japonicum eggs in hepatic portal tract. Source:By User:KGH - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=510508


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.
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