Ethnicity and prescription of analgesia in an accident and emergency department: cross sectional study

Editor,

I read with interest the paper by Choi et al [1], on ethnicity and
analgesia in an accident & emergency department. Unfortunately, the
authors have failed to answer the question adequately. By failing to
reject the null hypothesis (that ethnicity has no effect on analgesia
prescribing in A&E) they allow the possibility of a type II error. No
power calculation has been performed to reassure readers how likely this
is, and hence the conclusions made by the authors that ethnicity is not a
risk factor, lack validity.

To detect a difference of 10% (say 80% vs. 70%) in prescribing rates
between two groups, with a ratio of 5:1 recruitment to the study and with
the significance level set at 5% and power of 90%; they would need 255
patients in the Bangladeshi group to show such a difference if it existed.
The published study would seem to have a 90% power to detect a significant
difference (at the 5% level) in proportions in the Bangladeshi group
compared to the White group only if the Bangladeshi group had a
prescribing rate of less than 55.3% or greater than 94.8%.[2] The
published study with an expected prescription rate of 78.5% in the White
group has a less than 30% power to detect a clinically significant
variation in prescribing of 10%, and thus the type II error rate is too
high (>70%)to allow any valid conclusions to be drawn.

The possibility of selection bias must also be considered. The small
number of subjects in the Bangladeshi group does not reflect well the
local population (14% of the study population vs. over 25% of the local
population). Additionally, no explanation is offered as to the lack of age
comparability (mean White age 33.8 vs. mean Bangladeshi age 25.9,
p<_0.05 between="between" the="the" two="two" groups.="groups." these="these" may="may" well="well" form="form" different="different" populations="populations" based="based" upon="upon" factors="factors" other="other" than="than" ethnicity.="ethnicity." authors="authors" state="state" that="that" no="no" attempt="attempt" was="was" made="made" to="to" adjust="adjust" for="for" potential="potential" confounding="confounding" although="although" some="some" were="were" measured="measured" and="and" a="a" more="more" robust="robust" logistical="logistical" regression="regression" model="model" allow="allow" greater="greater" interpretation="interpretation" of="of" data.="data." p="p"/> In summary, the authors contention that ethnicity does not affect
analgesic prescribing in their institution has yet to be proven. This is
an important issue where communication with patients in A&E
departments, particularly those who do not speak English, can be difficult
[3] and may affect our prescribing habits. I would like to see the
authors show more robustly how communication in their A&E department
with all ethnic groups has no impact upon patient care. as this is an
important and growing issue.

Dr Peter Leman

A&E Consultant

St Thomas' Hospital,
London
SE1 7EH

[1] Choi DMA, Yate P, Coats T, Kalinda P, Paul EA. Ethnicity and
prescription of analgesia in an accident and emergency department: cross
sectional study. BMJ. 2000:320:980-1.

[2] CLINSTAT software. St George's Hospital Medical School. London.
1994.

[3] Leman P, Williams DJ. Questionnaire survey of interpreters in
accident and emergency departments in the UK. Journal of Accident &
Emergency Medicine 1999;16(4):271-4.