ORIGINAL RESEARCH

Lack of effect on blood alcohol level ofswabbing venepuncture sites with 70%isopropyl alcoholemm_1248 9..12

Alicia Tucker1 and Christopher Trethewy2

1Department of Emergency Medicine, Royal Brisbane & Women’s Hospital, Brisbane, Queensland and2Department of Critical Care, Tamworth Hospital, Tamworth, New South Wales, Australia

Abstract

Objective: It is standard practice to clean the skin using a non-alcohol-containing swab before forensicblood alcohol sampling, because of the belief that the use of an alcohol-containing swab willcontaminate the sample. The present study aimed to determine whether cleaning the skinwith 70% isopropyl alcohol swabs, before venepuncture, alters measured blood alcohollevel (BAL).

Methods: Volunteers aged >18 years had paired venous blood tests, which were drawn within 2 minof each other. One arm was swabbed with a 70% isopropyl alcohol swab and allowed to drybefore venepuncture. The other was swabbed with saline, and these concurrent sampleswere used as controls. BAL was tested using the enzymatic method. Pathologists analysingthe samples were blinded to the swabbing technique used. The mean differences andstandard deviations of each of the paired samples were analysed using Student’s t-test.

Results: Fifty-six paired venous blood samples were obtained from volunteers. Mean BAL in theisopropyl alcohol-swabbed group was 3.27 mg/dL with a standard deviation of 1.14 mg/dL.Mean BAL in the saline-swabbed group was 3.41 mg/dL with a standard deviation of1.11 mg/dL. The mean difference was 0.14 mg/dL, with a standard error of 0.157. Therewas no statistically significant difference between the groups.

Conclusions: The present study demonstrated that the use of 70% isopropyl alcohol swabs does notsignificantly affect BAL when used before venepuncture. This has implications that chal-lenge current forensic blood alcohol sample acquisition.

Key words: alcohol, blood alcohol, ethanol, isopropyl alcohol, swab, venepuncture.

Introduction

Forensic blood alcohol levels (BAL) are taken every dayin ED throughout Australia. According to mandatory

state laws,1 medical staff are legally required to take ablood sample for alcohol analysis in any patient who isover 15 years of age, who has been involved in an acci-dent on a road or road-related area, whether they are a

Correspondence: Dr Alicia Tucker, Staff Specialist, Department of Emergency Medicine, Royal Hobart Hospital, Liverpool Street, Hobart,Tas. 7001, Australia. Email: aftucker@gmail.com

Alicia Tucker, MB BS (Hons), BMedSci, FACEM, Staff Specialist; Christopher Trethewy, BSc (Medical), MB BS (Hons), FACEM, EmergencyPhysician and Director of Emergency Medicine Training.

doi: 10.1111/j.1742-6723.2009.01248.x Emergency Medicine Australasia (2010) 22, 9–12

© 2009 The AuthorsJournal compilation © 2009 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine

driver, passenger or pedestrian. Departmental andpolice protocols state that the venepuncture/i.v. cannu-lation site should be swabbed with a non-alcohol-containing swab. This is because of the perceived riskthat any form of alcohol in a swab might alter theapparent BAL, leading to false positive readings,2–4

which, in turn, would have legal implications.Although it has never been shown that cleaning the

skin with alcohol swabs before venepuncture or injec-tion results in lower infection rates,5–7 practitioners inAustralian ED traditionally use 70% isopropyl alcohol(isopropanol) swabs for cleaning the skin beforevenepuncture. If these swabs are inadvertently usedbefore obtaining a BAL, as might occur in a busytrauma situation, the sample cannot, theoretically, beused for forensic testing. In order to comply with theRoad Safety Acts,1 a second, separate, blood samplemust be obtained by the practitioner. This exposes thepatient to another painful procedure, increases the bloodproduct exposure risk to the practitioner and the patientand takes time for the medical practitioner or registerednurse.

There is little research that looks specifically at theuse of isopropanol swabs to clean the skin before bloodalcohol testing and its effect on measured BAL. Thereare a number of studies that looked at the effect of usingethanol swabs on BAL. Three studies demonstrated astatistically significant elevation of BAL following theuse of these swabs. Each study adopted a variety ofswabbing techniques: allowing the site to dry, samplingwhile the skin was wet and removing the needle whilecompressing the sample site with the swab. Peek et al.demonstrated a mean difference between ethanol-swabbed and un-swabbed samples of 6.95 � 6.7 mg/dL.8 Carter and McConnell found that three out of 24ethanol-swabbed blood samples taken from volunteers,who had abstained from alcohol, had BAL of up to112 mg/dL (0.112 gm%).9 In 2005, Higuchi and Kuriharafound that 34 out of 120 samples had uptake concentra-tion differences between 30 and 400 mg/dL.10 Thesevalues have legal implications, as the legal blood alcohollimit in Australia is up to 50 mg/dL (0.05 gm%).

Research involving the use of isopropyl alcoholswabs is limited and under-powered. Miller and Rosinexamined whether intensive use of alcohol hand sani-tizing agents raised apparent BAL.11 A retrospective,incidental finding of the study was published online.12

Researchers found that in eight blood samples takenusing isopropyl alcohol swabs there was no detectableBAL.12 There were, however, no control samples used inthe present study.

Peek et al.8 and McIvor and Cosbey13 completedstudies on 24 and 20 volunteers, respectively, who hadsamples taken with isopropyl alcohol compared withnon-alcohol swabs. BAL was analysed using gas chro-matography. Neither study showed a statistically sig-nificant alteration in measured BAL.

The present study aimed to determine whether clean-ing the skin with 70% isopropyl alcohol swabs, beforevenepuncture, alters measured BAL.

Methods

The study was conducted in October 2007 at the ED ofthe Tamworth Hospital, NSW. Volunteers aged>18 years had paired venous blood tests drawn by asingle assistant. The latter was independent of thestudy. Sample size was calculated based on a perceivedclinically (and potentially forensically) relevant BAL dif-ference of 1 mg/dL (0.001 gm%) and mean BAL attainedin the Peek et al.8 study to achieve a power of 0.8 (a <0.05, b 0.2). The volunteers were obtained from adults(patients and staff) who were present in the ED on thestudy days and who provided written informed consent.Participant alcohol consumption history was notrequired as they would be acting as their own controls.The left arm was swabbed five times with a 70% iso-propyl alcohol swab (Medi-Swab, Smith & Nephew PtyLtd, North Ryde, NSW, Australia) and allowed to dry30 s before venepuncture. The right arm was swabbedwith saline using the same application technique andthese samples were concurrently used as controls.

Samples were drawn within 2 min of each other.Venepuncture was performed using a standard 21-Gneedle with the Vacutainer system (Becton DickinsonPty Ltd, North Ryde, NSW, Australia) in the antecubitalfossa. Two millilitres of blood was collected directly intoa sodium fluoride/K3EDTA tube. Specimens werestored in accordance with the reagent guidelines andrun as a batch to avoid inter-batch variability.

Blood alcohol level was tested using the enzymaticmethod14 (Synchron LX system, Beckman Coulter Aus-tralia Pty Ltd, Yeerongpilly, Qld, Australia). In thismethod, ethanol is converted to acetaldehyde by alcoholdehydrogenase and nicotinamide adenine dinucleotide(NAD). The NAD is reduced to NADH that shows anincreased absorbancy at 340 nm. According to reagentguidelines, isopropyl alcohol does not interfere with thisreaction at physiological levels (<2000 mg/dL). Qualitycontrol is maintained with calibration against a solutionof known ethanol concentration. The BAL, mean

A Tucker and C Trethewy

10 © 2009 The AuthorsJournal compilation © 2009 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine

differences and standard deviations of the pairedsamples were then analysed using the Student’s t-test.

The present study was approved by the Hunter NewEngland Human Research Ethics Committee (07/09/19/4.03).

Results

Fifty-six paired venous blood samples were obtainedfrom volunteers, one using a 70% isopropyl alcoholswab and a second using a saline swab. BAL weremeasured in each sample and the results were analysed(Table 1).

Mean BAL in the isopropyl alcohol swabbed groupwas 3.27 mg/dL. Mean BAL in the saline swabbedgroup was 3.41 mg/dL. The mean difference was0.14 mg/dL (Table 2). There was no statistically signifi-cant difference between the groups.

Discussion

Our study showed that the use of isopropyl alcoholswabs before venepuncture does not affect measuredBAL. This challenges the current mandatory practice ofusing a non-alcohol-containing swab before forensicblood alcohol testing. This result could make it easierto collect forensic samples in the future and reduce thenecessity to take separate forensic and clinically indi-cated blood samples. This will decrease blood productexposure risk, and avoid repeated, painful procedureson patients in our ED.

Two methods are used by laboratories to measureBAL, including gas chromatography and the enzymaticmethod, such as the Synchron LX system. The latter isused in most hospital-based units and the former is usedin most forensic units. Gas chromatography with flame

ionization detection is considered the universal goldstandard in forensic labs because it is rapid, accurate,reproducible and readily automated.15 The enzymaticmethod is thought to be as unsuitable for use in forensicinvestigations, as it is less accurate than gas chroma-tography at differentiating between ethanol and isopro-panol in blood.15 We did not find that the isopropylswabs altered the BAL in our subjects, although deter-mining the accuracy of the enzymatic method in theforensic setting was beyond the scope of the presentstudy.

For the present study to legally challenge the currentuse of non-alcohol-containing swabs on forensic BALtesting the samples would need to be tested within aforensic laboratory as well. Unfortunately, our accesswas limited to the Syncron LX system, although infuture studies we would enlist the assistance of theforensic laboratories.

Limitations

All participants in the present study had low BAL,although it is expected that the findings could beextrapolated over a range of BAL. Also, in the context ofclinical practice, the technique of how the isopropylalcohol swabs are used might differ from the standard-ized method used in the study.

These are factors that could be investigated by con-ducting further research in this area.

Conclusions

Current practice mandates a non-alcohol-containingswab before the collection of forensic blood alcoholtests. The present study demonstrated that using theenzymatic method for BAL analysis, the use of 70%isopropyl alcohol swabs did not significantly affectBAL when used before venepuncture.

Acknowledgements

AT wishes to thank Dr Don Clauson, Pathology NewEngland, Tamworth, for his help in the data collection

Table 1. Blood alcohol levels (BAL) in samples from isopropylalcohol-swabbed and saline-swabbed arms

n = 56 BAL (mg/dL) SD (mg/dL)

Isopropyl alcohol swab 3.27 �1.14Control (saline) swab 3.41 �1.11

Table 2. T-test analysis of paired blood alcohol samples

Mean (mg/dL) 95% Confidence interval t Significance (two-tailed)

Difference (isopropyl–saline) -0.139 -0.454–0.177 -0.881 0.382

Isopropyl swabs and blood alcohol testing

11© 2009 The AuthorsJournal compilation © 2009 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine

in the present study. AT also wishes to thank Dr RicTodhunter, Nambour Hospital, for his constructive com-ments in the manuscript’s development.

Author contributions

AT conceived and designed the study. AT organizeddata collection, entry and interpretation under thesupervision of CT. AT wrote the manuscript.

Competing interests

None declared.

Accepted 27 October 2009

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12 © 2009 The AuthorsJournal compilation © 2009 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine