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'''Original Editors ''' - [[User:Alexander Ghyssels|Alexander Ghyssels]]  
'''Original Editors ''' - [[User:Alexander Ghyssels|Alexander Ghyssels]]  as part of the [[Vrije Universiteit Brussel Evidence-based Practice Project|Vrije Universiteit Brussel Evidence-Based Practice Project]]


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== Introduction&nbsp;<ref>J.G. Seiler et al. Essentials of hand surgery, American society for surgery of the hand, lippincot Williams and Wilkins, 2002</ref><ref>Andrew Ronald et al. Is the Allen's test adequate to safely confirm that a radial artery may be harvested. CardioVasc Thorac Surg 2005;4:332-340</ref><ref>Christine B. Novak. Outcome Following Conservative Management of Thoracic Outlet Syndrome. J Hand Surg 1995;20A:542-548.)</ref><ref>Adam J. Hansen. Reverse Radial Forearm Fascial Flap With Radial Artery Preservation. American Association for Hand Surgery 2007</ref>  ==


*The Allen test is a worldwide used test to determine whether the patency of the radial or ulnar artery is normal. It is performed prior to radial cannulation or catheterisation, because placement of such a catheter often results in thrombosis. Therefore the test is used to reduce the risk of ischemia to the hand. The Allen test can also be used to gather information preceding removal of the radial artery for a coronary bypass graft.<br>
== Purpose  ==
*<span>&nbsp;</span>A positive Allen’s test means that the patient does not have dual blood supply to the hand, which is a negative indication for catheterisation or removal of the radial arteries.
*There is also a digital Allen’s test, which is used to assess the arterial supply to the fingers.<br>


== Clinically Relevant Anatomy<ref>Joints and associated structures of the hand, University of Michigan medical school, 1995</ref><ref>S. Moses, Cardiovascular medicine book, family practise notebook,  20/02/2011</ref>  ==


*The supply in the arm starts in the neck between the scalenus muscles. It is the subclavian artery who supply the arm from above. The subclavian artery becomes the arteria axillaris, who becomes after 3 inches an arteria brachialis. In the region af the elbow (fossa cubita) divides the arteria in two pieces: the ulnar artery and the radial artery.<br>  
The Allen test for blood flow was first described in 1929 by Edgar V. Allen as a non-invasive evaluation of the arterial patency of the hand in patients with thromboangitis obliterans. <ref name=":2">Allen E. Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative cases. The American Journal of the Medical Sciences. 1929;178(2):237-243. </ref>,<ref>Asif M & Sarkar, P. Three-Digit Allen's Test. Annals of Thoracic Surgery. 2007; 84 (2):686-687. </ref>  
*<span>&nbsp;</span>The hand has a complex and rich vascular network, which in most cases is provided by the radial and ulnar artery.
*The radial artery runs between the musculus brachioradialis and musculus flexor carpi radialis. At the wrist, it splits into a superficial branch to contribute to the superficial palmar arch. The other branch crosses dorsally deep to the tendons of the anatomic snuffbox to form the deep palmar arch.  
*The ulnar artery lies under the musculus flexor carpi ulnaris. At the wrist it enters the Guyons canal, where it splits into a deep palmar branch and a superficial palmar branch. The superficial palmar branch forms the superficial palmar arch, while the deep branch contributes to the deep palmar arch.
*Since the radial as well as the ulnar arteries both form anastomosis (cfr. the deep and superficial palmar arch) the blood supply of the hand is ensured even if one of the arteries is occluded, In that case the other one can take charge of the blood supply.<br>


== Epidemiology&nbsp; ==
The test has since been adapted as the Modified Allen test (MAT). In Allen's original test, both hands were tested simultaneously by the examiner compressing one artery of each hand at the same time. The MAT efficiently evaluates the adequacy of the collateral circulation but requires the testing of one hand at a time. <ref>Fuhrman T, Pippin W, Talmage L & Reilley T. Evaluation of collateral circulation of the hand. Journal of Clinical Monitoring (1992); 8(1):28-32
</ref>


In 3% of the hospitalised patients an inadequate collateral blood supply was diagnosed by Allen’s test.'''&nbsp;'''<br> <br>
The Allen test is a first-line standard test used to assess the arterial blood supply of the hand <ref name=":0">Oettlé A, van Niekerk A, Boon J, Meiring J. Evaluation of Allen’s test in both arms and arteries of left and right-handed people. Surgical and Radiologic Anatomy. 2006;28(1):3-6. </ref>. This test is performed whenever intravascular access to the radial artery is planned or for selecting patients for radial artery harvesting, such as for coronary artery bypass grafting or for forearm flap elevation <ref>Andrew Ronald et al. Is the Allen's test adequate to safely confirm that a radial artery may be harvested. CardioVasc Thorac Surg 2005;4:332-340</ref><ref name=":0" /><ref>Adam J. Hansen. Reverse Radial Forearm Fascial Flap With Radial Artery Preservation. American Association for Hand Surgery 2007</ref>.


== Differential Diagnosis<ref>Adam J. Hansen. Reverse Radial Forearm Fascial Flap With Radial Artery Preservation. American Association for Hand Surgery 2007</ref>  ==
The Allen test is part of the diagnostic work-up for vascular abnormalities of the upper limb such as in thoracic outlet syndrome (TOS) <ref name=":0" />. In thoracic outlet syndrome and specifically vascular TOS, one possible cause can be the compression of the subclavian artery or vein as it passes through the interscalene triangle by the muscle bodies of the scalene where there can be muscular hypertrophy.


The allen’s test can be an instrument for different disorders.<br>The test can be used for all the diseases with insufficient vascularisation in the arm. A thoracic outlet syndrome is an example for that.<br>A compartiment syndrome can also be investigated by an allen test.<br>But it is most frequently used after a bypass operation of the hand. With a good interpretation of the test, the surgeon can see if the blood supply is normal in the hand.
== Clinically Relevant Anatomy  ==
The hand has a complex and rich vascular network, which is mostly supplied by the radial and ulnar arteries.


*Two arteries normally supply blood to the hand. The blood flow in both arteries is stopped until your hand becomes pale.<br>
The radial artery runs between the brachioradialis and flexor carpi radialis muscles of the forearm and at the wrist splits into a superficial branch to contribute to the superficial palmar arch. The other branch crosses dorsally deep to the tendons of the anatomic snuffbox to form the deep palmar arch <ref>Woon C. Blood Supply to Hand - Hand - Orthobullets [Internet]. Orthobullets.com. 2018 [cited 14 July 2018]. Available from: <nowiki>https://www.orthobullets.com/hand/6007/blood-supply-to-hand</nowiki></ref>.
*<span>&nbsp;</span>Blood is then allowed to flow through the artery that will not be used to collect the blood sample.
*If this artery is working well, your hand will quickly regain its normal color. This means that an accidental injury to the artery used for collecting the blood sample will not completely block all blood flow to your hand.
*If the artery that will not be used to collect the blood sample is not working well, your hand will remain pale. The Allen test will then be performed on your other hand. If it also remains pale, the blood often will be collected from another artery, usually in the groin or elbow crease.<br><br>


== Diagnostic Procedures<ref>Marek Brzezinski et al. Radial Artery Cannulation: A Comprehensive Review of Recent Anatomic and Physiologic Investigations. Anesth Analg 2009;109:1763–81)</ref> ==
The ulnar artery lies under flexor carpi ulnaris of the forearm and at the wrist enters the Guyons canal, where it splits into a deep palmar branch and a superficial palmar branch. The superficial palmar branch forms the superficial palmar arch, while the deep branch contributes to the deep palmar arch <ref name=":3" />.


The allen’s test is frequently used for looking if the radial artery is usefull for a coronary bypass grafting. <br>The therapist has to interpret the results carefully. <br>If the hand becomes bleach at the 3 first digits, there is a lack in the radial artery. <br>
Since the radial and ulnar arteries both form anastomosis (the deep and superficial palmar arch) the blood supply of the hand is ensured even if one of the arteries is occluded,


== Examination&nbsp;<ref name="magee">David J Magee : Orthopedic Physical Assessment:fifth edition; In:Forearm,Wrist and Hand;Chapter seven;pg-445-446.</ref> ==
{{#ev:youtube|https://www.youtube.com/watch?v=lRjF5wI_IqU}}<ref name=":3">AnatomyZone. Upper Limb Arteries - Hand and Wrist - 3D Anatomy Tutorial [Internet]. 2018 [cited 14 July 2018]. Available from: <nowiki>https://www.youtube.com/watch?v=lRjF5wI_IqU</nowiki></ref>


The patient is asked to open and close the hand several times as quickly as possible and then squeeze the hand tightly . The examiner's thumb and index finger are placed over the radial and ulnar arteries, compressing them . As an alternative technique, the examiner may use both hands ,placing one thumb over each artery to compress the artery and placing the fingers on the posterior aspect of the arm for stability. The patient then opens the hand while pressure is maintained over the arteries. One artery is tested by releasing the pressure over that artery to see if the hand flushes. The other artery is then tested in a similiar fashion. Both hands should be tested for comaprison .&nbsp;<br><br>
== Technique  ==


<br>
==== The Allen Test for blood flow ====


== Specificity &amp; Sensitivity&nbsp;<ref name="martin">A. Martin et al. Reliability of Allen’s test in selection of patients for radial artery harvest, The society of thoracic surgeons. Ann Thorac Surg 2000;70:1362-1365</ref> ==
The radial artery is located by palpation at the proximal skin crease of the wrist and then compressed with three digits. The ulnar artery is similarly located and then compressed with three digits. With both arteries compressed, the subject is asked to clench and unclench the hand 10 times. The hand is then held open, ensuring that the wrist and fingers are not hyperextended and splayed out. The palm is observed to be blanched. The ulnar artery is released and the time is taken for the palm and especially the thumb and thenar eminence to become flush is noted. If the capillary refill time is less than 6 seconds the test is considered positive. The test is then completed with the radial artery tested in a similar fashion <ref name=":1">Asif M, Sarkar P. Three-Digit Allen’s Test. The Annals of Thoracic Surgery. 2007;84(2):686-687. </ref>. Both hands should be tested for comparison.&nbsp;


'''Martin et al (2000)''' reported a sensitivity of 73.2% and a specificity 97.1%. Based on these findings we can establish that the Allen test is a good and valid screening test for the circulation of the hand.  
When performing the Allen test, hyperextension of the hand and wide separation of the fingers can lead to a false-negative result <ref name=":1" />. This is due to occlusion of the transpalmar arch, and parts of the fingers and palm will continue to remain blanched after release of the ulnar artery <ref>Greenhow D. Incorrect Performance of Allenʼs Test—Ulnar-artery Flow Erroneously Presumed Inadequate. Anesthesiology. 1972;37(3):356-357. </ref>. To prevent this from occurring the test should be performed with the hand partially open as described in Allen's <ref name=":2" /> original work.


<span>&nbsp;</span><br><br>
{{#ev:youtube|v=vUxP7bWFgK4}}<ref>Paula Humanatomy. The Allen's Test. Available from: <nowiki>https://www.youtube.com/watch?v=vUxP7bWFgK4</nowiki> </ref>


== Recent Related Research (from [http://www.ncbi.nlm.nih.gov/pubmed/ Pubmed]) ==
== Diagnostic Values & Interpretation ==
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During the Allen test, digital compression of both ulnar and radial arteries at the level of the proximal wrist crease is applied, which causes palmar blanching followed by release of compression on either artery, which causes hyperaemia in the non-diseased state.<ref name=":0" /> Adequate collateral circulation is indicated by a return of color to the hand within an adequate time period.


Based on a cut-off of 6 seconds on the Allen’s test the sensitivity was 54.5%, specificity of 91.7%, and diagnostic accuracy of 78.5%. At a cut-off of 5 seconds diagnostic accuracy was maximal (79.6%), with a sensitivity of 75.8% and specificity of 81.7%; 100% sensitivity occurred at a cut-off of 3 seconds, with specificity of 27% and diagnostic accuracy of 52% <ref name="martin">A. Martin et al. Reliability of Allen’s test in selection of patients for radial artery harvest, The society of thoracic surgeons. Ann Thorac Surg 2000;70:1362-1365</ref>.
The predictive value of a negative test is 0.8% and of a positive test is only 53% <ref>Husum B, Berthelsen P. Allen’s test and systolic arterial pressure in the thumb. British Journal of Anaesthesia. 1981;53(6):635-637.  </ref>.
== References  ==
== References  ==


<references /><br>
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[[Category:Special_Tests]]
[[Category:Primary Contact]]
[[Category:Wrist]]
[[Category:Hand]]
[[Category:Assessment]]
[[Category:Wrist - Assessment and Examination]]
[[Category:Hand - Assessment and Examination]]
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[[Category:Hand - Special Tests]]

Latest revision as of 23:10, 31 January 2021

Original Editors - Alexander Ghyssels as part of the Vrije Universiteit Brussel Evidence-Based Practice Project

Top Contributors - Sue Safadi, Alexander Ghyssels, Sheik Abdul Khadir, Claire Knott, Admin, Rachael Lowe, Scott Cornish, Kim Jackson, Tarina van der Stockt, Magdalena Hytros, George Prudden, Kai A. Sigel, WikiSysop and Shaimaa Eldib  

Purpose[edit | edit source]

The Allen test for blood flow was first described in 1929 by Edgar V. Allen as a non-invasive evaluation of the arterial patency of the hand in patients with thromboangitis obliterans. [1],[2]

The test has since been adapted as the Modified Allen test (MAT). In Allen's original test, both hands were tested simultaneously by the examiner compressing one artery of each hand at the same time. The MAT efficiently evaluates the adequacy of the collateral circulation but requires the testing of one hand at a time. [3]

The Allen test is a first-line standard test used to assess the arterial blood supply of the hand [4]. This test is performed whenever intravascular access to the radial artery is planned or for selecting patients for radial artery harvesting, such as for coronary artery bypass grafting or for forearm flap elevation [5][4][6].

The Allen test is part of the diagnostic work-up for vascular abnormalities of the upper limb such as in thoracic outlet syndrome (TOS) [4]. In thoracic outlet syndrome and specifically vascular TOS, one possible cause can be the compression of the subclavian artery or vein as it passes through the interscalene triangle by the muscle bodies of the scalene where there can be muscular hypertrophy.

Clinically Relevant Anatomy[edit | edit source]

The hand has a complex and rich vascular network, which is mostly supplied by the radial and ulnar arteries.

The radial artery runs between the brachioradialis and flexor carpi radialis muscles of the forearm and at the wrist splits into a superficial branch to contribute to the superficial palmar arch. The other branch crosses dorsally deep to the tendons of the anatomic snuffbox to form the deep palmar arch [7].

The ulnar artery lies under flexor carpi ulnaris of the forearm and at the wrist enters the Guyons canal, where it splits into a deep palmar branch and a superficial palmar branch. The superficial palmar branch forms the superficial palmar arch, while the deep branch contributes to the deep palmar arch [8].

Since the radial and ulnar arteries both form anastomosis (the deep and superficial palmar arch) the blood supply of the hand is ensured even if one of the arteries is occluded,

[8]

Technique[edit | edit source]

The Allen Test for blood flow[edit | edit source]

The radial artery is located by palpation at the proximal skin crease of the wrist and then compressed with three digits. The ulnar artery is similarly located and then compressed with three digits. With both arteries compressed, the subject is asked to clench and unclench the hand 10 times. The hand is then held open, ensuring that the wrist and fingers are not hyperextended and splayed out. The palm is observed to be blanched. The ulnar artery is released and the time is taken for the palm and especially the thumb and thenar eminence to become flush is noted. If the capillary refill time is less than 6 seconds the test is considered positive. The test is then completed with the radial artery tested in a similar fashion [9]. Both hands should be tested for comparison. 

When performing the Allen test, hyperextension of the hand and wide separation of the fingers can lead to a false-negative result [9]. This is due to occlusion of the transpalmar arch, and parts of the fingers and palm will continue to remain blanched after release of the ulnar artery [10]. To prevent this from occurring the test should be performed with the hand partially open as described in Allen's [1] original work.

[11]

Diagnostic Values & Interpretation[edit | edit source]

During the Allen test, digital compression of both ulnar and radial arteries at the level of the proximal wrist crease is applied, which causes palmar blanching followed by release of compression on either artery, which causes hyperaemia in the non-diseased state.[4] Adequate collateral circulation is indicated by a return of color to the hand within an adequate time period.

Based on a cut-off of 6 seconds on the Allen’s test the sensitivity was 54.5%, specificity of 91.7%, and diagnostic accuracy of 78.5%. At a cut-off of 5 seconds diagnostic accuracy was maximal (79.6%), with a sensitivity of 75.8% and specificity of 81.7%; 100% sensitivity occurred at a cut-off of 3 seconds, with specificity of 27% and diagnostic accuracy of 52% [12].

The predictive value of a negative test is 0.8% and of a positive test is only 53% [13].

References[edit | edit source]

  1. ↑ 1.0 1.1 Allen E. Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative cases. The American Journal of the Medical Sciences. 1929;178(2):237-243.
  2. ↑ Asif M & Sarkar, P. Three-Digit Allen's Test. Annals of Thoracic Surgery. 2007; 84 (2):686-687.
  3. ↑ Fuhrman T, Pippin W, Talmage L & Reilley T. Evaluation of collateral circulation of the hand. Journal of Clinical Monitoring (1992); 8(1):28-32
  4. ↑ 4.0 4.1 4.2 4.3 Oettlé A, van Niekerk A, Boon J, Meiring J. Evaluation of Allen’s test in both arms and arteries of left and right-handed people. Surgical and Radiologic Anatomy. 2006;28(1):3-6.
  5. ↑ Andrew Ronald et al. Is the Allen's test adequate to safely confirm that a radial artery may be harvested. CardioVasc Thorac Surg 2005;4:332-340
  6. ↑ Adam J. Hansen. Reverse Radial Forearm Fascial Flap With Radial Artery Preservation. American Association for Hand Surgery 2007
  7. ↑ Woon C. Blood Supply to Hand - Hand - Orthobullets [Internet]. Orthobullets.com. 2018 [cited 14 July 2018]. Available from: https://www.orthobullets.com/hand/6007/blood-supply-to-hand
  8. ↑ 8.0 8.1 AnatomyZone. Upper Limb Arteries - Hand and Wrist - 3D Anatomy Tutorial [Internet]. 2018 [cited 14 July 2018]. Available from: https://www.youtube.com/watch?v=lRjF5wI_IqU
  9. ↑ 9.0 9.1 Asif M, Sarkar P. Three-Digit Allen’s Test. The Annals of Thoracic Surgery. 2007;84(2):686-687.
  10. ↑ Greenhow D. Incorrect Performance of Allenʼs Test—Ulnar-artery Flow Erroneously Presumed Inadequate. Anesthesiology. 1972;37(3):356-357.
  11. ↑ Paula Humanatomy. The Allen's Test. Available from: https://www.youtube.com/watch?v=vUxP7bWFgK4
  12. ↑ A. Martin et al. Reliability of Allen’s test in selection of patients for radial artery harvest, The society of thoracic surgeons. Ann Thorac Surg 2000;70:1362-1365
  13. ↑ Husum B, Berthelsen P. Allen’s test and systolic arterial pressure in the thumb. British Journal of Anaesthesia. 1981;53(6):635-637.
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