Onchocerciasis other diagnostic studies: Difference between revisions

Jump to navigation Jump to search
m (Changes made per Mahshid's request)
 
(3 intermediate revisions by 2 users not shown)
Line 6: Line 6:
==Other Diagnostic Studies==
==Other Diagnostic Studies==
===Skin Snip Biopsy===
===Skin Snip Biopsy===
The gold standard test for the diagnosis of onchocerciasis remains the [[Skin biopsy|skin snip biopsy]]. The [[biopsy]] is performed using a [[sclerocorneal biopsy]] punch or by elevating a small cone of skin (3 mm in diameter) with a needle and shaving it off with a scalpel. This will result in the removal of around 2 mg of tissue. The [[tissue]] is then incubated in normal saline at room temperature for 24 hours to allow the microfilariae to emerge. The microfilariae can then be identified microscopically. The sites for the skin snip are usually over the [[iliac crest]], the [[scapula]], and the lower extremities. Six snips provide the most diagnostic sensitivity. Although the skin snip is highly specific, its sensitivity can be limited in the pre-patent stage of [[infection]], which can last 1 to 1.5 years, and in low intensity [[infection]]s. Performing [[polymerase chain reaction]] ([[PCR]]) of the skin snip can increase the sensitivity in these two situations, though this is not commercially available.
The gold standard test for the diagnosis of onchocerciasis remains the [[Skin biopsy|skin snip biopsy]]. The [[biopsy]] is performed using a sclerocorneal biopsy punch or by elevating a small cone of skin (3 mm in diameter) with a needle and shaving it off with a scalpel. This will result in the removal of around 2 mg of tissue. The [[tissue]] is then incubated in normal saline at room temperature for 24 hours to allow the microfilariae to emerge. The microfilariae can then be identified microscopically. The sites for the skin snip are usually over the [[iliac crest]], the [[scapula]], and the lower extremities. Six snips provide the most diagnostic sensitivity. Although the skin snip is highly specific, its sensitivity can be limited in the pre-patent stage of [[infection]], which can last 1 to 1.5 years, and in low intensity [[infection]]s. Performing [[polymerase chain reaction]] ([[PCR]]) of the skin snip can increase the [[sensitivity]] in these two situations, though this is not commercially available.
If a patient has skin [[nodule]]s caused by onchocercal infection, nodulectomy allows for the identification of macrofilariae in the [[tissue]]. [[Slit lamp]] eye exam can be used to visualize microfilariae in individuals with [[eye disease]].
If a patient has skin [[nodule]]s caused by onchocercal infection, nodulectomy allows for the identification of macrofilariae in the [[tissue]]. [[Slit lamp]] eye exam can be used to visualize microfilariae in individuals with [[eye disease]].
----
----
Line 17: Line 17:


===Antibody Tests===
===Antibody Tests===
There are antibody tests that can assist in the diagnosis of onchocerciasis, though many are not available outside the research setting. There is a general screen for any filarial infection (including Wuchereria, Brugia, Loa, and Mansonella infections) that is available in some specialty diagnostic labs. Because the test is highly sensitive, it is useful in determining if an individual has had filarial infection, but it is not specific enough to identify which filarial infection. As with any antibody test, the results indicate only that the patient has been exposed to the disease, but it cannot determine if the patient has an active infection. This distinction is less important in symptomatic travelers, but it limits the usefulness of the test in persons from endemic areas. One advantage of the test is that it can pick up evidence of infection in the pre-patent stage of infection. There are several Onchocerca-specific serologic tests in existence, such as the OV-16 antigen antibody test and the OV luciferase immunoprecipitation system (LIPS) assay, but these are currently only available in the research setting and are not approved for diagnosis in the United States.
There are antibody tests that can assist in the diagnosis of onchocerciasis, though many are not available outside the research setting. There is a general screen for any filarial infection (including Wuchereria, Brugia, Loa, and Mansonella infections) that is available in some specialty diagnostic labs. Because the test is highly sensitive, it is useful in determining if an individual has had filarial infection, but it is not specific enough to identify which filarial infection. As with any antibody test, the results indicate only that the patient has been exposed to the [[disease]], but it cannot determine if the patient has an active infection. This distinction is less important in symptomatic travelers, but it limits the usefulness of the test in persons from [[endemic]] areas. One advantage of the test is that it can pick up evidence of infection in the pre-patent stage of infection. There are several Onchocerca-specific serologic tests in existence, such as the OV-16 antigen antibody test and the OV luciferase immunoprecipitation system (LIPS) assay, but these are currently only available in the research setting and are not approved for diagnosis in the United States.
In general the diagnosis of O. volvulus infection should be made with skin snip. However, when skin snips are negative and clinical suspicion of infection is high, the general antibody test could be used in an attempt to exclude infection. If the general antibody test were positive, then it might be necessary to consider performing additional skin snips and/or seeking additional diagnostic information by enlisting the assistance of researchers who perform antibody tests.  
In general the diagnosis of O. volvulus infection should be made with skin snip. However, when skin snips are negative and clinical suspicion of infection is high, the general antibody test could be used in an attempt to exclude infection. If the general antibody test were positive, then it might be necessary to consider performing additional skin snips and/or seeking additional diagnostic information by enlisting the assistance of researchers who perform antibody tests.
 
== References ==
== References ==
{{reflist|2}}
{{reflist|2}}
Line 28: Line 29:
[[Category:Neglected diseases]]
[[Category:Neglected diseases]]
[[Category:Disease]]
[[Category:Disease]]
[[Category:Infectious disease]]

Latest revision as of 18:31, 18 September 2017

Onchocerciasis Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Onchocerciasis from other Diseases

Epidemiology and Demographics

Risk Factors

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Primary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Onchocerciasis other diagnostic studies On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

slides

Images

American Roentgen Ray Society Images of Onchocerciasis other diagnostic studies

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Onchocerciasis other diagnostic studies

CDC on Onchocerciasis other diagnostic studies

Onchocerciasis other diagnostic studies in the news

Blogs on Onchocerciasis other diagnostic studies

Directions to Hospitals Treating Onchocerciasis

Risk calculators and risk factors for Onchocerciasis other diagnostic studies

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Kalsang Dolma, M.B.B.S.[2]

Overview

The gold standard test for the diagnosis of onchocerciasis remains the skin snip biopsy. The biopsy is performed using a sclerocorneal biopsy punch or by elevating a small cone of skin (3 mm in diameter) with a needle and shaving it off with a scalpel. There are antibody tests that can assist in the diagnosis of onchocerciasis, though many are not available outside the research setting

Other Diagnostic Studies

Skin Snip Biopsy

The gold standard test for the diagnosis of onchocerciasis remains the skin snip biopsy. The biopsy is performed using a sclerocorneal biopsy punch or by elevating a small cone of skin (3 mm in diameter) with a needle and shaving it off with a scalpel. This will result in the removal of around 2 mg of tissue. The tissue is then incubated in normal saline at room temperature for 24 hours to allow the microfilariae to emerge. The microfilariae can then be identified microscopically. The sites for the skin snip are usually over the iliac crest, the scapula, and the lower extremities. Six snips provide the most diagnostic sensitivity. Although the skin snip is highly specific, its sensitivity can be limited in the pre-patent stage of infection, which can last 1 to 1.5 years, and in low intensity infections. Performing polymerase chain reaction (PCR) of the skin snip can increase the sensitivity in these two situations, though this is not commercially available. If a patient has skin nodules caused by onchocercal infection, nodulectomy allows for the identification of macrofilariae in the tissue. Slit lamp eye exam can be used to visualize microfilariae in individuals with eye disease.


Shown below is an image demonstrating a skin snip biopsy by elevating a piece of skin with a needle and shaving it off with a scalpel.


Shown below is an image demonstrating a skin snip biopsy using a sclerocorneal biopsy punch.


Antibody Tests

There are antibody tests that can assist in the diagnosis of onchocerciasis, though many are not available outside the research setting. There is a general screen for any filarial infection (including Wuchereria, Brugia, Loa, and Mansonella infections) that is available in some specialty diagnostic labs. Because the test is highly sensitive, it is useful in determining if an individual has had filarial infection, but it is not specific enough to identify which filarial infection. As with any antibody test, the results indicate only that the patient has been exposed to the disease, but it cannot determine if the patient has an active infection. This distinction is less important in symptomatic travelers, but it limits the usefulness of the test in persons from endemic areas. One advantage of the test is that it can pick up evidence of infection in the pre-patent stage of infection. There are several Onchocerca-specific serologic tests in existence, such as the OV-16 antigen antibody test and the OV luciferase immunoprecipitation system (LIPS) assay, but these are currently only available in the research setting and are not approved for diagnosis in the United States. In general the diagnosis of O. volvulus infection should be made with skin snip. However, when skin snips are negative and clinical suspicion of infection is high, the general antibody test could be used in an attempt to exclude infection. If the general antibody test were positive, then it might be necessary to consider performing additional skin snips and/or seeking additional diagnostic information by enlisting the assistance of researchers who perform antibody tests.

References

Template:WH Template:WS