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clinmed/1999120016v1 (December 29, 1999)
Contact author(s) for copyright information

An open prospective randomised trial to reduce the pain of blood glucose testing. Ear vs Thumb.

Simon D. Carley
Specialist Registrar in Emergency Medicine

Carole Libetta
Specialist Registrar in Emergency Medicine

Brian Flavin
Specialist Registrar in Emergency Medicine

John Butler
Specialist Registrar in Emergency Medicine

Nam Tong
Clinical Fellow in Emergency Medicine

Ian Sammy
Consultant in Emergency Medicine

Contributors:

SDC initiated and supervised the study, analysed the data and wrote the paper. IAS, BL, CL, NT & JB recruited patients and assisted in writing the paper. All authors participated in the design of the study. SDC is the guarantor of the study.

Funding; Nil
Conflict of interest: Nil
Correspondance to: Simon Carley, SpR in Emergency Medicine,
Hope Hospital, Stott Lane, Salford 0161 787 4848
E-mail: s.carley{at}btinternet.com

Abstract

Objective: To compare the pain of testing when taking a blood glucose sample from either the ear or the thumb.

Design: Open unblinded prospective randomised controlled trial.

Setting: The Emergency Medicine department of a university-affiliated hospital.

Subjects: 60 patients; aged ³ 16 requiring a random blood glucose test. Patients were excluded if they were dysphasic, less than Alert on the AVPU scale, known to have a bleeding disorder or if they had paraesthesia, anaesthesia or lesions at any of the test sites.

Main Outcome measures: 1) Self reported pain by 100mm visual analogue scale; 2) Success rate by intention-to-test

Results: 60 patients completed the protocol. The medican pain score for ear sampling was 2mm as compared to 8.5mm in the thumb group, this was statistically significant (p=0.01). There were 5 failures in the ear group as compared to 2 in the thumb group (p=0.42)

Conclusions: The pain of lancet testing at both sites is low. Emergency lancet skin puncture in adults is likely to be less painful if carried out in the ear rather than the thumb.

Key words. Blood glucose testing, pain, lancet.

Introduction

The assessment of random blood glucose is one of the most commonly performed minimally invasive procedures in clinical practice. Traditionally, blood is sampled from a digit using a skin lancet to obtain a sample of blood suitable for analysis. The digits are chosen for their accessibility and rich blood supply. However, they are also some of the most sensitive sites on the human body making the procedure painful for many patients.

A recent paper showed that lancet sampling from the side of the thumb was less painful than lancet sampling from the finger or from venepuncture at the elbow [1]. During that study the earlobe was suggested as an alternative sample site, as it is also accessible and vascular.

The aim of this study was to test the null hypothesis that there would be no difference in pain score, or success rate, for blood glucose testing between lancet skin puncture sites on the thumb or earlobe.

Methods

An prospective unblinded randomised controlled design was proposed. This received approval from the Salford and Trafford Health Authority Research Ethics Committee.

Study population

The study was conducted in the Emergency Department of Hope Hospital over a 3 week period. Patients were recruited to the trial at times when a Middle grade or Consultant in Emergency Medicine was available in the department. All patients in whom a blood glucose test was requested during these times were eligible. Patients were excluded if they were aged less than 16, dysphasic, less than alert on the AVPU scale [2], had a bleeding disorder, or had altered sensation (including pain) or a lesion at any of the test sites.

Study design

Eligible consenting patients were randomised to one of two intervention groups: 1)earlobe sampling; 2) thumb sampling. Treatment allocations were prepared in a series of sealed opaque envelopes. Patient allocations were randomised using a computer generated random number list (MS Excel 1997, Microsoft Corporation, Seattle, USA.).

Sampling procedure

The skin at the site of sampling was cleaned, then wiped with a sterile dry swab to reduce potential interference with the sample. Lancet skin puncture was performed on the lateral aspect of the thumb or on the earlobe. The Unistik 2 device was used (Owen Mumford, Oxford, UK). The area surrounding the test site was squeezed to express a drop of blood.

If the proscribed sampling method failed to provide an adequate sample for successful glucometry the failure was recorded, and the test was repeated using lancet puncture on the lateral aspect of the thumb until sampling was achieved.

Pain was assessed using a 100mm visual analogue scale (VAS) [3]. The number of successful 1st attempts was recorded for each technique. Additional outcomes were adverse events, and withdrawal from the trial.

Statistical Power

An a priori power calculation suggested that approximately 30 patients would be required in each treatment group to achieve an 90% power of detecting a 20mm difference on the visual analogue scale between groups.

Statistical Methods

Analysis was by intention to test. Non-parametric data was analysed using using Mann-Whitney U tests. Categorical variables were compared using Chi-squared analysis with Yates correction.

Results

60 patients were recruited into the trial, 30 were assigned to each treatment group. The patients were comparable following randomisation (table 1). (need to define ‘previous test’ for clarity).

TABLE ONE

Characteristic

Ear group

n=30

Thumb Group

n=30

Statistical Significance

Mean Age

52 years

54 years

p=0.88

Diabetics

5 (16%)

7 (23%)

p=0.52

Male

17 (56%)

13 (43%)

p=0.79

Previous test

13 (43%)

19 (63%)

p=0.12

Pain associated with the test

Figure 1 shows the distribution of pain scores. The median pain score was 2mm in the ear group compared with 8.5mm in the thumb group. This was statistically significant (p=0.01). Failure rates were similar There were 5 first time failures in the ear group compared with 2 in the thumb group, this was not statistically significant (p=0.42).

FIGURE 1

Adverse Events

There were no clinical adverse events.

Discussion

This study has demonstrated that the pain experienced during lancet skin puncture of the earlobe is less than that experienced when blood is taken from the thumb. The difference in median pain scores is small which reflects the relatively low levels of pain experienced during this procedure. However, the widespread use of this sampling technique means that even a small reduction in pain is clinically important.

The reasons for the difference in pain between ear and thumb is unclear. It is possible that the density of nocioceptors is less in the ear than the thumb. In addition, the difference may be influenced by patient perception, particularly as the patient can see the thumb or digits being tested, but they cannot see the ear.

The failure rate was low with both procedures although slightly higher for sampling from the ear. This study was too small to detect a true difference if one exists. As the data was analysed on an intention to test basis the increase in failure rate does not appear to have influenced the overall pain scores. The trial investigators felt that the flow of blood from the ear was less reliable than that from the thumb, requiring more squeezing. Further work is required to address this factor as it was not addressed in this study.

For obvious reasons it was not possible to blind the patient or the tester to the proscribed method. However, blinding could have been introduced when asking patients to complete the VAS. For practical reasons this was not possible.

The limitations of this study, particularly the lack of any data on repeat testing at the same site, will be apparent to those caring for patients who require frequent monitoring. Further research on selected patient groups may be required. However, our findings are applicable whenever a small sample of blood is required, for example random blood glucose or haemoglobin testing.

Summary

If a random blood glucose test is required, blood should be obtained by lancet puncture of the skin on the earlobe rather than by lancet puncture of the thumb.

References

  1. Loveland ME, Carley SD, Cranfield N, Hillier VF, Mackway-Jones K. Assessment of the pain of blood-sugar testing: a randomised controlled trial. Lancet 1999;354: 961
  2. Committee on trauma (1993). Advanced Trauma Life Support Program for Physicians, 5th Edition. Chicago: American College of Surgeons.
  3. Huskisson EC. Measurement of Pain Lancet 1974;ii:884-886

 





This Article
Right arrow Abstract Freely available
Services
Right arrow Similar articles in this netprints
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Carley, S. D.
Right arrow Articles by Sammy, I. A.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Carley, S. D.
Right arrow Articles by Sammy, I. A.
Related Collections
Right arrow Anaesthesia:
Pain

Right arrow Endocrinology:
Diabetes

Right arrow Evidence Based Practice:
Diagnostics

Right arrow Statistics and Research Methods:
Randomised Controlled Trials: examples


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