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Belgian Toxicology and Trauma study (B T T S):
research methodology
L. Van Camp
BTTS research group, U niversity H ospitals o f L euven, D epartm ent o f E m ergency M edecine,
H erestraat 49, B 3000 Leuven.
ABSTRACT
T his study includes m otor vehicle and bicycle di
-ors o f age o r older, w ho w ere
adm itted to one o f the 5 selected m ajor E .D .’s and had to stay for at least 24 hours o r died in
the hospital, after having been involved in a road traffic accident on a public road.
From January 16, 1995 to June 15, 1996, accident victim s have been prospectively screened
for alcohol, pharm aceuticals and illicit drugs (am phetam ines, barbiturates, benzodiazepines,
cannabis, cocaine, m ethadone, opiates and propoxyphene). In addition a questionnaire,
regarding driving experience, accident tim e, place and dynam ics, social status, risk behaviour,
m edical history, alcohol and drug consum ption, has been com pleted. In every subject, all
injuries have been docum ented and coded with the A bbreviated Injury Scale, 1990 revision
(AIS90).
T his m ethod allows: firstly to quantify the problem o f alcohol and drugs in traffic accidents in
relation to gender, age, social profile, pre-existing m edical condition, tim e, type and dynam ics
o f accident, type o f vehicle(s) involved and injury severity, secondly to identify eventually
populations at risk and finally to develop prevention as well as legal actions in dealing with
this problem .
K eyw ords:
Ethanol, Psychotropic drugs, Traffic accidents, Traum a, Injury severity.
PURPOSE
The purpose o f this study w as firstly to quantify the problem o f alcohol and drugs in traffic
accidents in relation to gender, age, social profile, pre-existing m edical condition, tim e, type
and dynam ics o f accident, type o f vehicle(s) involved and injury severity and secondly to
identify eventually p opulations at risk. T he research findings should be useful in the
developm ent o f prevention as well as legal actions in dealing with this problem .
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POPULATION AND STUDY SAMPLE
The population o f interest are drivers o f a m otorvehicle or bicycle, excluding children under
the age o f 14, who are severely injured after they have been involved in a road traffic accident
on the Belgian roads.
M ultistage sam pling was perform ed. First, a selecting o f hospitals w as m ade and secondly a
consecutive patient sam ple was taken in every hospital. T his sam pling m ethod w as m ainly
chosen for pragm atic reasons. At one hand, the selected hospitals had to be com m ited and had
to dispose o f a sufficient developed toxicology laboratory. A t the other hand, the selection o f
hospitals took in m ind the representativity and reliability o f the sam ple. T he cooperating
hospitals had to be sufficiently spread over the country and had to adm it their prim ary traffic
accident victim s from both rural and urban areas, w ith a for B elgium representative set of
roads. In addition, em ergency departm ents (E.D.'s) who serve a big region (population) were
preferred in order to lim it the num ber o f cooperating hospitals. This was im portant to keep the
study cost within reasonable limits, but also to m axim alize the inter-rater reliability.
B ased on these considerations, five m ajor traum a centres have been selected. From January
16, 1995 to June 15, 1996, all patients w ho m et the inclusion criteria w ere included in the
sample. The criteria were: driver o f a m otorvehicle or bicycle, 14 years o f age or older, being
prim ary (w ithin
6
hours after the accident and w ithout prior adm ission to another E .D .)
adm itted for at least one day, or death, due to injury sustained as a result o f a road traffic
accident on a public road or its direct environm ent.
To avoid selection bias, secondary transfered patients w ere not included. In general, these
patients are m ore severely injured and, by definition, the site o f accident is not situated in the
selected sam ple areas. Patients w ho entered the E.D . m ore than
6
hours after the accident
w ere not included because their toxicological laboratory results w ere considered inaccurate
(especially in the case o f ethanol).
T he population definition "severely injured", w hich is rather vague, is translated in the
inclusion criteria into adm ission for at least one day, or death, as a result o f the sustaining
injuries. In a small m inority o f patients the same injuries could have lead to adm ission as well
as no adm ission, depending on the individual descision o f the physision o f record. This could
result in a m inor representativity problem . A nother problem w ith the representativity o f the
sam ple is due to the deaths at scene. These victim s have probably sustained the m ost severe
injuries but could not always be included due to certain lim itations (e.g. legal lim itation).
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T he representativity o f the study sam ple increased by including also those patients who
should have been adm itted for at least one day, but left the hospital sooner against m edical
advise.
DATA COLLECTION
D ata collection existed out o f four separate parts: (1) collection o f inform ation regarding the
accident by the police, (2 ) collection o f inform ation partly based on a face to face interview in
the hospital, (3) toxicological analysis on blood and urine sam ples, (4) detailed description,
coding en quantification o f the sustained injuries.
Police reports, questionnaires and blood and urine sam ples w ere collected, identified with an
anonym ous code, and m ailed to the central epidem iological centre by the local study co ­
ordinator in every E.D. To avoid decoding o f toxicological results by the local study co­
ordinators, these results w ere reported directly to the epidem iological centre.
In a face to face interview a questionnaire regarding driving licence and experience, social
profile (e.g. m arital state, level o f education, profession), risk behaviour (e.g. use o f protective
devices such as a seat belt or helm et), m edical history, alcohol and drug consum ption,
accident time, place and dynam ics, vehicles involved, w eather conditions and state o f the
road, w as com pleted. On the sam e form the sustaining injuries w ere described in detail,
together w ith the length o f hospital stay, sex, age, physiological param eters (i.e. G lasgow
Com a Scale, respiratory rate and systolic blood pressure) at first m edical contact, discharge
place (e.g. revalidation centre, hom e,...) and status (dead or alive). P roxy inform ants (e.g.
fam ily, friends) w ere only allow ed to answ er on those questions for w hich it w as clear they
could provide an exact an reliable answer.
B lood sam ples w ere taken w ithin
8
hours after the accident. T he first urine w as collected
w ithin 24 hours. F or reasons o f representativity o f the toxicological results, the ethical
com m ittees allowed sam pling o f blood and urine w ithout inform ed consent.
Untill screening, all sam ples were preserved at 4°C. E thanol w as analysed w ithin 7 days on
fluoride oxalate blood by Radiative E nergy Attenuation (REA) on an A D x analyzer. Positive
sam ples (ethanol > 0 .1 g/L) w ere confirm ed by G as C hrom atoghraphy Flam e Ionisation
D etection (G C-FID ) in a central laboratory. Pharm eceuticals and illicit drugs w ere screened
within tw o w eeks in the local toxicology laboratory o f the hospital and further preserved at 20°C untill confirm ation. P ositive sam ples w ere confim ed p e r substance in a central
laboratory. Table 1 gives an overview o f the substances analysed, the applied laboratory tests
for screening and confirm ation and the cut-off values for every substance.
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Table 1: substances analysed, applied laboratory tests for screening and confirmation
and cut-off values per substance.
Substance
Screening
Cut-off
Confirmation
Ethanol
REA on blood
0,10 g/L
G C FID on blood
Am phetam ines
FPIA on urine
300 ng/m L
G C MS on urine
Barbiturates
FPIA on urine
200 ng/m L
G C N PD on serum
Benzodiazepines
FPIA on urine
50 ng/m L
H P L C on serum &
FPIA on serum
12 ng/m L
G C E C D on serum
Cannabinoids
FPIA on urine
25 ng/m L
G C MS on urine
Cocaine & m etabolites
FPIA on urine
300 ng/m L
G C MS on urine
Methadone
FPIA on urine
300 ng/m L
G C MS on urine
Opiates
FPIA on urine
200 ng/m L
G C MS on urine
Propoxyphene
FPIA on urine
300 ng/m L
G C MS on urine
Legen:
G C ECD =
Gas Chrom atography Electron C apture detection
G C FID =
Gas C hrom atography F lam e Ionisation D etection
G C MS =
Gas C hrom atography M ass Spectrom etry
G C NPD =
Gas C hrom atography N itrogen Phosphor D etection
FPIA =
Fluorescence Polarisation Im m uno A ssay
HPLC =
High Pressure Liquid C hrom atography
REA =
Radiative Energy Attenuation
In addition carbohydrate deficient transferrin (CDT), a m arker indicating high chronic alcohol
consum ption (Behrens et al., 1988) (Stibler, 1991) (Allen et al., 1994) (Bell et al.,1994), was
analysed
Based on the physiological param eters at first m edical contact, the R evised T raum a Score
(Cham pion et al., 1989) w as com puted. The anatom ic injuries were centrally coded w ith the
Abbreviated Injury Scale (AIS90) (Association for the A dvancem ent o f A utom otive M edicine
-A A A M -, 1990) by a A A A M certified coder. B ased on the RTS a nd/or A IS 90 codes, the
severity o f the sustaining injuries was quantified by the Injury Severity Score (ISS) (B aker et
al., 1974) (Baker et al.,1976) (Copes et al., 1988), the A natom ic Profile (A P) (Copes et al,
1990) and A Severity Characterization o f Traum a (ASCOT) (Cham pion et al., 1990).
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