# Allen's test

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{{Short description|Medical sign used in physical examination of arterial blood flow to the hands}}
{{Infobox diagnostic
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| purpose         =examination of arterial blood flow to the hands
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In [medicine](/source/medicine), '''Allen's test''' or the '''Allen test''' is a [medical sign](/source/medical_sign) used in [physical examination](/source/physical_examination) of [arterial blood](/source/arterial_blood) flow to the hands. It was named for [Edgar Van Nuys Allen](/source/Edgar_Van_Nuys_Allen), who described the original version of the test in 1942.<ref name="allenoriginal">{{cite journal |vauthors=Allen EV |title=Thromboangiitis obliterans: methods of diagnosis of chronic arterial lesions distal to the wrist with illustrative cases |journal=Am J Med Sci |volume=178 |issue=3 |pages=165–189 |date=1929 |doi=10.1097/00000441-192908000-00009|pmid=19312256 |pmc=1933752 }}</ref>

An altered test, first suggested by [Irving S Wright](/source/Irving_S_Wright) in 1952, has almost universally replaced the original method in contemporary medical practice. The alternative method is often referred to as the '''modified Allen's test''' or '''modified Allen test'''.<ref name=":0" />

==Method==
===Original test===
The original test proposed by Allen is performed as follows:<ref name="allenoriginal"/>
# The patient is asked to clench both fists tightly for 1 minute at the same time.
# Pressure is applied over the [radial](/source/Radial_artery) and [ulnar arteries](/source/Ulnar_artery) simultaneously so as to occlude them.
# The patient then opens the fingers of both hands rapidly, and the examiner compares the colour of both. The initial [pallor](/source/pallor) should be replaced quickly by [rubor](/source/rubor).
# The test may be repeated, this time occluding the ulnar arteries.

===Modified test===
In the modified Allen test, one hand is examined at a time:<ref name=":0" />
# The patient is asked to clench their fist for about 30 seconds.
# Pressure is applied over the ulnar and the radial arteries so as to occlude both of them.
# Still elevated, the hand is then opened. It should appear blanched (pallor may be observed at the finger nails).
# Ulnar pressure is released while radial pressure is maintained, and the colour should return within 5 to 15 seconds.

If color returns as described, Allen's test is considered to be normal. If color fails to return, the test is considered abnormal and it suggests that the [ulnar artery](/source/ulnar_artery) supply to the hand is not sufficient.<ref name=":0">{{Cite web|title = Modified Allen test|url = https://www.ncbi.nlm.nih.gov/books/NBK138652/|date = 2010-01-01|last1 = National Center for Biotechnology|agency = U. S. National Library of Medicine|publisher = World Health Organization}}</ref>

== Significance ==
The modified Allen's test is also performed prior to [heart bypass surgery](/source/Coronary_artery_bypass_surgery). The [radial artery](/source/radial_artery) is occasionally used as a conduit for bypass surgery, and its patency lasts longer in comparison to the [saphenous vein](/source/Great_saphenous_vein)s. Prior to heart bypass surgery, the test is performed to assess the suitability of the radial artery to be used as a conduit. A result of less than 3 seconds is considered as good and suitable. A result of between 3–5 seconds is equivocal, whereas the radial artery will not be considered for [grafting](/source/Graft_(surgery)) if the result is longer than 5 seconds.<ref>{{cite journal |url=https://www.nejm.org/doi/full/10.1056/NEJMoa1716026 |doi=10.1056/NEJMoa1716026 |title=Radial-Artery or Saphenous-Vein Grafts in Coronary-Artery Bypass Surgery |date=2018 |last1=Gaudino |first1=Mario |last2=Benedetto |first2=Umberto |last3=Fremes |first3=Stephen |last4=Biondi-Zoccai |first4=Giuseppe |last5=Sedrakyan |first5=Art |last6=Puskas |first6=John D. |last7=Angelini |first7=Gianni D. |last8=Buxton |first8=Brian |last9=Frati |first9=Giacomo |last10=Hare |first10=David L. |last11=Hayward |first11=Philip |last12=Nasso |first12=Giuseppe |last13=Moat |first13=Neil |last14=Peric |first14=Miodrag |last15=Yoo |first15=Kyung J. |last16=Speziale |first16=Giuseppe |last17=Girardi |first17=Leonard N. |last18=Taggart |first18=David P. |author19=RADIAL Investigators |journal=New England Journal of Medicine |volume=378 |issue=22 |pages=2069–2077 |pmid=29708851 |hdl=1983/da0c0152-dab6-4cc0-aca6-60fc9b131219 |hdl-access=free }}</ref>

The utility of the modified Allen's test is questionable,<ref name="pmid11081899">{{cite journal |last1=Jarvis |first1=MA |last2=Jarvis |first2=CL |last3=Jones |first3=R |last4=Spyt |first4=TJ |title=Reliability of Allen's test in selection of patients for radial artery harvest |journal=Ann. Thorac. Surg. |volume=70 |issue=4 |pages=1362–5 |date=October 2000 |pmid=11081899 |doi= 10.1016/S0003-4975(00)01551-4|doi-access=free }}</ref> and no direct correlation with reduced ischemic complications of radial artery cannulation have ever been proven.  In 1983, Slogoff and colleagues reviewed 1,782 radial artery cannulations and found that 25% of them resulted in complete radial artery occlusion, without apparent adverse effects.<ref>{{cite journal |last1=Slogoff |first1=S |last2=Keats |first2=AS |last3=Arlund |first3=C |year=1983 |title=On the safety of radial artery cannulation. |journal=Anesthesiology |volume=59 |issue=1 |pages=42–7 |pmid= 6859611|doi= 10.1097/00000542-198307000-00008|doi-access=free }}</ref> A number of reports have been published in which permanent ischemic sequelae occurred even in the presence of a normal Allen's test.<ref>{{cite journal |last1=Thompson |first1=SR |last2=Hirschberg |first2=A |year=1988 |title=Allen's test re-examined. |journal=Crit Care Med |volume=16 |issue=9 |pages=915 |pmid= 3402240|doi=10.1097/00003246-198809000-00025}}</ref><ref>{{cite journal |last=Wilkins |first=RG |year=1985 |title=Radial artery cannulation and ischaemic damage: A review. |journal=Anaesthesia |volume=40 |issue=9 |pages=896–899 |pmid= 3901815|doi= 10.1111/j.1365-2044.1985.tb11055.x|url=https://deepblue.lib.umich.edu/bitstream/2027.42/72040/1/j.1365-2044.1985.tb11055.x.pdf |hdl=2027.42/72040 |s2cid=10669033 |hdl-access=free }}</ref> In addition, the results of Allen's tests do not appear to correlate with  distal blood flow as demonstrated by fluorescein dye injections.<ref>{{cite journal |last=McGregor |first=AD |year=1987 |title=The Allen test – an investigation of its accuracy by fluorescein angiography. |journal=J Hand Surg Br Vol |volume=12 |issue=1 |pages=82–85 |pmid= 3572188|doi= 10.1016/0266-7681(87)90065-9}}</ref><ref>{{cite journal |last1=Stead |first1=SW |last2=Stirt |first2=JA |year=1985 |title=Assessment of digital blood flow and palmar collateral circulation. |journal=Journal of Clinical Monitoring and Computing|volume=2 |issue=1 |pages=29–34 |doi= 10.1007/bf02915870|pmid=3835222 |s2cid=39584943 }}</ref>

Further modifications to the test have been proposed to improve reliability.<ref name="pmid17643672">{{cite journal |last1=Asif|first1= M|last2=Sarkar|first2=PK |title=Three-digit Allen's test |journal=Annals of Thoracic Surgery |volume=84 |issue=2 |pages=686–687 |date=August 2007 |pmid=17643672 |doi=10.1016/j.athoracsur.2006.11.038 }}</ref>

==References==
{{reflist|2}}

{{Cardiovascular system symptoms and signs}}

Category:Diagnostic intensive care medicine
Category:Diagnostic surgery
Category:Symptoms and signs: Vascular

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Adapted from the Wikipedia article [Allen's test](https://en.wikipedia.org/wiki/Allen's_test) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Allen's_test?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.