Faculty of Medicine of the University of Porto
Department of Biostatistics and Medical Informatics
2005/06
Drug Hypersensitivity
Prevalence in the Adult
Population
Group 13
Table of contents

Introduction
– Aim
Participants and Methods
 Results
 Discussion and Limitations
 Website project

2
Introduction

Drug hypersensitivity reactions are the side
effects of drugs taken at a dose that is
tolerated by normal subjects1

Drug hypersensitivity reactions are thought
to represent one-third of adverse drug
reactions1
1- Gomes et al. Self-reported drug allergy in a general adult Portuguese population. Clin Exp Allergy 2004; 34:1597-1601
3
Introduction
80% of adverse drug reactions are
predictable (type A reactions)2
 Type B reactions are not predictable, are
dose independent, are not related with the
pharmacologic actions of the drug and are
extremely important because they are often
serious and can cause death2,3
 Allergic reactions are one of the examples of
unpredictable reactions3

2 - Gruchalla R. Drug metabolism, danger signals, and drug-induced hypersensitivity. J Allergy Clin Immunol October 2001
3 –Gruchalla R. Understanding drug allergies. J Allergy Clin Immunol June 2000
4
Introduction
Drug hypersensitivity is a common and
complicated problem in clinical practice4
 It shows in various forms of autoimmune
diseases4
 Diagnosis of drug hypersensibility is difficult4
 Drug-allergic reactions are underdiagnosed4

4– Demoly, P, Kropf, R:, Bircher A. et Pichler W.J. Drug hypersensitivity: questionnaire. Allergy 1999, 54, 999-1003
5
Introduction
3-7% of the population experience an
adverse drug reaction1
 5% of all hospital admissions are due to
adverse drug reactions2
 Fatal adverse drug reactions are between
the 4th and 6th leading cause of death of
hospitalized patients in the USA3

1 - Gomes et al. Self-reported drug allergy in a general adult Portuguese population. Clin Exp Allergy 2004; 34:1597-1601
2 - Gruchalla R. Drug metabolism, danger signals, and drug-induced hypersensitivity. J Allergy Clin Immunol October 2001
3 - Gruchalla R. Understanding drug allergies. J Allergy Clin Immunol June 2000
6
Introduction

Drugs most commonly observed as the
cause of these reactions3:
– ampicillin
– amoxicillin
– trimethoprim-sulfamethoxazole
– penicillin
3 - Gruchalla R. Understanding drug allergies. J Allergy Clin Immunol June 2000
7
Introduction

Common diseases and symptoms provoked
by drug hypersensitivity4:
– Exanthema (most common)
– Urticaria
– Anaphylaxis
– Blood cell dyscrasia
– Fever
– Intersticial lung disease
– Hepatitis
– Nephritis
© Dermatology database of
Institute for Biomedical
Informatics, Faculty of
Medicine, Ljubljana, Slovenia
4– Demoly, P, Kropf, R:, Bircher A. et Pichler W.J. Drug hypersensitivity: questionnaire. Allergy 1999, 54, 999-1003
8
Aim
To determine the lifetime prevalence of drug
hypersensitivity in the adult population
9
Secondary Aims
Identify the drugs that are more frequently
associated to hypersensitive reactions,
(classifying them using the same system of
INFARMED data base);
 Describe the different types of allergic
expression;
 Relate the allergic reactions already
described with the presence of some
diseases;

10
Study participants





Target population - all adult people (above 18
years old) living in Porto region
Available population - all adult people living in
Porto region with telephone in their household
Unit of Analysis – single person
Inclusion Criteria – be an adult, have phone in their
household, live in Porto and have capacities to
answer the questionnaire properly
Exclusion Criteria – see flowchart
11
Flowchart
12
Study design
Observational, cross-sectional and
descriptive study, executed via phone
interviews.
 Data collection method – Phone interviews,
filling up a questionnaire previously designed
 Sample selection method – two stages
random digit dialling
 Frequency measurement – lifetime
prevalence

13
Random Digit Dialling5
Two Stages RDD Sampling Methods
 Will be used relative to the telephone
numbers of Porto region.
 Software will randomly select digits of the
type 22xxxxx and generate prefix numbers
 Software will randomly select two digits and
generate suffix numbers

5 - Groves, R et al. Telephone Survey Methodology. John Wiley & Sons Inc 2001
14
Random Digit Dialling
15
Data collection methods
Telephone interview
 Questionnaire

16
Main variables description
Presence of drug allergies in a life time
period
 Reaction type (skin, respiratory, digestive,
others)
 Suspected drug
 Presence of allergic diseases
 Other diseases
 Age
 Sex

17
Statistical Analysis
We will use SPSS® 13.0 software
 Descriptive statistics and hypothesis t tests
shall be used to analyse data
 We will use odds ratio as an association
measure

18
Results
Results of the phone calls made until 10th March 06
15%
7%
5%
Household - answered questionnaire
Household - refused to answer
Not a Household - not available
23%
Not a Household - commercial
Not a Household - others
50%
Total number of calls: 649
19
Results
Characterization of the people that answered the
questionnaire
7
6
5
women
men
4
3
2
Total = 39
Mean = 53,41
Median = 53,5
Missing values = 6
1
0
18-27
28-37
38-47
48-57
58-67
68-77
78-87
88-97
20
Expected Results

We expect that our study reveals about 37% of adverse drug reactions in our
population as reported1
1- Gomes et al. Self-reported drug allergy in a general adult Portuguese population.
21
Results
In your life, have you had problems or felt sick after taking a
drug?
20%
9
Yes
No
36
80%
Total: 45
22
Results
In your life, have you had problems or felt sick after taking a
drug?
4%
13%
Had problems but not
confirmed by a doctor
2
6
7%
3
had allergy - confirmed by
a doctor
No problems and no
allergy confirmed
34
76%
Had allergy confirmed by a
doctor but never had
problems
Total: 45
23
Results
Frequency of the allergy symptoms
8
7
6
5
4
3
2
1
0
skin
respiratory
others
digestive
24
Results
Drugs that gave rise to problems
5
4
3
penicillin
2
1
0
missed data
NSAID
antibiotic
25
Results
Allergies to drugs by age group
30%
25%
20%
15%
had problems
10%
5%
0%
18 to 40
41 to 60
more than 60
26
Results
27
Main limitations
Telephone interviews may not be accurate
enough to determine whether a reaction is
really of hypersensitivity or not
 People living in Porto, without a telephone at
home are excluded
 Interviews were done in a restricted period of
time
 Very low response rate

28
Discussion - difficulties

Questionnaire introduction was not very
appropriate:
– excessive extension;
– complexity of phrasal structure and lexicon;

Low cooperation of the inquired population:
– difficulties to understand what was being said (advanced
age);
– lack of time (active class);

Slanting of the inquired population due to the
impossibility of making phone calls during all day:
– majority of the population inquired was of advanced age;
– phone calls made only in the morning and afternoon;
– active population excluded;
29
Discussion - difficulties

Difficulties to contact the resident:
– the person who answered the phone didn’t live there and was
incapable to give us an hour for future contacting;
– Most of the times, the person who was next to celebrate birthday
was impossible to reach;

Lots of unfruitful phone calls:
– most of the numbers dialed were not available;
– great part of the available phone numbers were not residences;
– this lead to a waste of precious time;

When the first combination of prefix and suffix was a
residence, the majority of next ones weren’t either:
– we had to make dozens of phone calls with the same prefix to
obtain five residences.
30
Gantt chart

Microsoft Project
31
Website project
Home
Abstract
Abstract in portuguese
Introduction
Participants and Methods
Results
Discussion
Conclusions
References
Authors and contacts
Full article (pdf)
Work package
Gantt chart
Presentations
SPSS sintax
SPSS tables
Related websites
32
References
1 - Gomes et al. Self-reported drug allergy in a general adult
Portuguese population. Clin Exp Allergy 2004; 34:15971601
2 - Gruchalla, Rebecca. Drug metabolism, danger signals, and
drug-induced hypersensitivity. J Allergy Clin Immunol
October 2001
3 - Gruchalla, Rebecca. Understanding drug allergies. J
Allergy Clin Immunol June 2000
4 - Demoly, P, Kropf, R:, Bircher A. et Pichler W.J. Drug
hypersensitivity: questionnaire. Allergy 1999, 54, 999-1003
5 - Groves, R et al. Telephone Survey Methodology. John
Wiley & Sons Inc 2001
33
The End