neurología

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Neurología. 2011;26(6):337-342
NEUROLOGÍA
NEUROLOGÍA
www.elsevier.es/ neurologia
Publicación Oicial de la Sociedad Española de Neurología
Volumen 25 • Número 1 • Enero-Febrero 2010
25
años
ORIGINAL ARTICLE
Metric properties of the Spanish version of the Lake Louise Acute
Mountain Sickness Questionnaire
F.J. Carod-Artal, a, * D. Ezpeleta Echávarri, b A.L. Guerrero Peral c
a
Servicio de Neurología, Hospit al Virgen de la Luz, Cuenca, Spain
Servicio de Neurología, Hospit al General Universit ario Gregorio Marañón, Madrid, Spain
c
Servicio de Neurología, Hospit al Clínico Universit ario de Valladolid, Valladolid, Spain
b
Received on 30t h July 2010; accept ed on 13t h December 2010
KEYWORDS
Met ric at t ribut es;
Migraine;
Int ernal consist ency;
Lake Louise
Quest ionnaire;
Mount ain sickness;
Validit y
Abstract
Obj ect ives: To assess t he met ric propert ies of t he Lake Louise Acut e Mount ain Sickness
(LLAMSQ) ive-item questionnaire.
Met hods: At t he end of t he course “ Neuroscience in pre-Columbian Andean cult ures”
(Peru, 2009), t he part icipant s answered t he self-report ed version of t he LLAMSQ. The
following psychomet ric at t ribut es were explored: accept abilit y (observed versus possible
scores; loor and ceiling effects), scaling assumptions (item-total correlation >0.30),
int ernal consist ency (Cronbach¿s alpha), precision (st andard error of measurement ), and
convergent and discriminat ive validit y. Differences in mean score of LLAMSQ bet ween
sympt omat ic acut e mount ain sickness subj ect s and asympt omat ic ones were calculat ed.
Result s: The part icipant s st ayed for days at Cuzco (3,400 met ers above sea level, MASL),
Sacred valley (2,850 MASL) and Machu Picchu (2,450 MASL). Sevent y people (60% males;
mean age 50±8 years; 88.6%neurologist s) were included in t he st udy. LLAMSQ mean score
was 3.36±2.02 (median 3; skewness 0.61). Ceiling and loor effects were 7.3% and 1.4%,
respect ively. Cronbach¿s alpha was 0.61, and st andard error of measurement 1.26.
LLAMSQ mean score signiicantly correlated (r=0.41, P=.002) with physical items (ataxia,
dyspnoea, tremor, mental symptoms). LLAMSQ mean scores were signiicantly higher
(worse) in t hose subj ect s who present ed wit h acut e sickness mount ain (5.8 vs 3.0; MannWhit ney, P<.0001).
Conclusions: Metric properties of the LLASMQ Spanish version are adequate. This
questionnaire seems to be useful in the early detection of high-altitude illness.
© 2010 Sociedad Española de Neurología. Published by Elsevier España, S.L. All right s
reserved.
* Corresponding aut hor.
E-mail: fj carod-art al@hot mail.com (F.J. Carod-Art al).
0213-4853X/ $ - see front mat t er © 2010 Sociedad Española de Neurología. Published by Elsevier España, S.L. All right s reserved.
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338
PALABRAS CLAVE
At ribut os mét ricos;
Cefalea;
Consist encia int erna;
Cuest ionario Lago
Louise;
Mal de alt ura;
Validez
F.J. Carod-Art al et al
Propiedades métricas de la versión española del Cuestionario de Mal de Altura
del Lago Louise
Resumen
Obj et ivos: Evaluar las propiedades mét ricas de la versión española del Cuest ionario de
Mal de Alt ura del Lago Louise (CMALL) aut oaplicado de 5 ít ems.
Mét odos: Tras el curso-seminario «Neurociencia en las cult uras andinas precolombinas»
(Perú, 2009), se entregó una encuesta a los participantes que incluía el CMALL. Se evaluó
la acept abilidad de los ít ems (punt uaciones observadas vs valores posibles, efect os t echo
y suelo), asunciones escalares (correlación ítem-total > 0,30), consistencia interna (alfa
de Cronbach), precisión (error est ándar de la medida) y validez de convergencia y discriminante. Esta última se evaluó calculando el valor medio del CMALL entre aquellos neurólogos que creían haber presentado mal de altura frente a quienes no lo habían present ado.
Result ados: Est ancia por días en alt ura: Cuzco 3.400 m sobre el nivel del mar (msnm),
Valle Sagrado (2.850 msnm) y Machu Picchu (2.450 msnm). Se incluyeron 70 suj et os (60%
varones, edad media 50 ± 8 años, 88,6% neurólogos). El valor medio del CMALL fue 3,36
± 2,02 (mediana 3, asimet ría 0,61). Los efect os t echo y suelo fueron 7,3 y 1,4%. El alfa
de Cronbach fue 0,61 y el error est ándar de la medida 1,26. El CMALL se correlacionó
signiicativamente (r = 0,41, p = 0,002) con los ítems de exploración física (ataxia, disnea, temblor, síntomas mentales). Las puntuaciones del CMALL fueron signiicativamente
mayores (peores) en quienes presentaron mal de altura (5,8 vs 3,0; Mann-Whitney, p <
0,0001).
Conclusiones: Las propiedades mét ricas de la versión española del CMALL parecen ser
adecuadas. Est e cuest ionario puede ser út il en la det ección precoz del mal de alt ura.
© 2010 Sociedad Española de Neurología. Publicado por Elsevier España, S.L. Todos los
derechos reservados.
Introduction
Exposure t o alt it ude in subj ect s who are not acclimat ised
can cause acut e mount ain sickness, charact erised by a
combinat ion of signs and sympt oms, many of t hem of
a neurological nat ure, where headache is t he main
sympt om. 1 Insomnia, fat igue, feeling of dizziness and
inst abilit y, anorexia and nausea are also common. 2,3 The
most serious forms of acut e mount ain sickness can cause
high alt it ude cerebral oedema. In sympt omat ic subj ect s,
t here is usually a cert ain individual suscept ibilit y, as well as
a lack of prior acclimat isat ion. 4
Some people can somet imes present high alt it ude
headache, where t he headache occurs above 2,500m and
cannot be at t ribut ed t o any ot her cause. 5 The diagnost ic
crit eria for alt it ude headache according t o t he second
edit ion Int ernat ional Headache Societ y6 classiication are
summarised in t able 1.
There are currently no adapted questionnaires in Spain
t o assess acut e mount ain sickness. The aim of t his st udy was
t o analyse t he met ric propert ies of t he Spanish version of
the Lake Louise Acute Mountain Sickness (LLAMSQ) ive-item
self-report ed Quest ionnaire, which is t he most commonly
known and used questionnaire for detecting acute mountain
sickness. 7 The direct applicat ion of t he English version of
the questionnaire, with no prior adaptation to other
languages or cult ural cont ext s, can cause diagnost ic
failures. 8
There are other more complex questionnaires that assess
acut e mount ain sickness, such as t he Environment al
Sympt oms Quest ionnaire (ESQ), consist ing of 67 it ems wit h
Acut e Mount ain Sickness subscales and Respirat ory
Sympt oms. 9,10 Unlike these more complex questionnaires,
the LLAMSQ can be quickly applied to clinical practice. The
scores obt ained are useful for screening by healt h personnel
in a rescue process or t o make t reat ment and evacuat ion
decisions high in t he mount ains.
Methods
Participants
The individuals included in t he st udy were part icipant s in a
neurological hist ory seminar-course “ Neuroscience in PreColumbian Andean Cult ures” held in Peru during February
2009. Once t he course was complet ed, t he part icipant s
were handed a survey t hat collect ed socio-demographic
dat a, pat hological hist ory, as well as t he LLAMSQ and
Headache at High Alt it udes Quest ionnaire.
Lake Louise Acute Mountain Sickness Questionnaire
The Lake Louise AMS scoring syst em was made up of
2 sections, a questionnaire on symptoms and a section for
clinical examinat ion. 7
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Met ric propert ies of t he Spanish version of t he Lake Louise Acut e Mount ain Sickness Quest ionnaire
Table 1
339
Table 3 Assessment syst em for t he self-report ing Lake
Louise Acut e Mount ain Sickness Quest ionnaire
Diagnost ic crit eria for alt it ude headache
A. Headache wit h at least 2 of t he following
charact erist ics and t hat complies wit h crit eria C
and D:
1. Bilat eral
2. Front al or front o-t emporal
3. Dull or oppressive quality
4. Mild t o moderat e int ensit y
5. Is aggravat ed by exercise, movement , effort ,
coughing or when bending over
B. Ascent t o an alt it ude above 2,500m
C. The headache develops during the irst 24hrs of the
ascent
D. The headache goes away in the irst 8hrs after the
descent
The symptoms questionnaire comprised 5 items on which
t he part icipant s t hemselves could respond: Headache,
Nausea and vomit ing, Fat igue/ t iredness, Dizziness/
confusion and Sleep Disorders (t able 2). The t ot al score of
the questionnaire was 15 points and could be clinically
useful when diagnosing and monit oring t he sympt oms of
acut e mount ain sickness in people exposed t o it .
Table 2 Individual it ems on t he self-report ing Lake Louise
Acut e Mount ain Sickness Quest ionnaire
Headache
No headache
Mild headache
Moderat e headache
Severe, incapacit at ing headache
0
1
2
3
Nausea and vomit ing
No nausea and vomit ing
Anorexia or mild nausea
Moderat ely int ense nausea and/ or vomit ing
Serious nausea and/ or vomit ing
0
1
2
3
Fat igue/ t iredness
No fat igue or t iredness
Mild fat igue or t iredness
Moderat ely int ense fat igue or t iredness
Serious fat igue or t iredness
0
1
2
3
Dizziness/ conf usion
No dizziness
Mild dizziness
Moderat e dizziness
Severe, incapacit at ing dizziness
0
1
2
3
Sleep disorders
None
I haven’ t slept as well as usual
I woke up several t imes; I’ ve slept badly
I’ ve hardly been able t o sleep at all
0
1
2
3
Clinical assessment
A. Changes in ment al st at e
No changes in ment al st at e
Let hargy
Disorient at ion or confusion
St upor or unconsciousness
B. At axia
No at axia
Carries out manoeuvres t o maint ain balance
Falls to the loor
Cannot remain st anding
C. Peripheral oedema
No peripheral oedema
Peripheral oedema in one place
Peripheral oedema in t wo or more places
Functional score
Overall, if you have had any sympt oms, how much
did it af f ect your act ivit ies?
No reduct ion in act ivit ies
Slight reduct ion in act ivit ies
Moderat e reduct ion in act ivit ies
Severe reduct ion in act ivit ies
0
1
2
3
0
1
2
3
0
1
2
3
0
1
2
3
Acut e Mount ain Sickness diagnosis is primarily based on
t he presence of a main sympt om, t he headache —even if
mild—which is associat ed t o a st ay at high alt it ude over t he
previous few days wit h t he presence of at least one ext ra
symptom and a score of 3 or more in the questionnaire. A
score of 3 t o 5 shows mild acut e mount ain sickness and a
score of 6 or more shows severe acut e mount ain sickness.
The questionnaire of symptoms can be carried out via a
clinical int erview, or more commonly wit h a self-report ed
one. The self-report ing version of LLAMSQ adapt ed t o
Spanish was t he subj ect of t his st udy, wit h lat er psychomet ric
analysis. The scale was adapt ed and t ranslat ed (EnglishSpanish) by t he aut hors in search of a bet t er semant ic
adapt at ion wit h t he purpose of making a correct applicat ion
of it wit hout inducing comprehension errors in t he it ems
used.
The second part of t he assessment syst em (a clinical
examinat ion t hat can be carried out by individuals on t heir
own, but t hat is normally carried out by t rained healt h st aff)
is useful t o ident ify t he progress of acut e mount ain sickness
t owards alt it ude cerebral oedema aft er ment al st at e, at axia
and presence of peripheral oedema is assessed. This part
includes a funct ional score t hat assesses t he impact of any
sympt om on everyday life act ivit ies (t able 3).
Psychometric analysis
The following met ric propert ies for LLAMSQ were assessed:
quality of the data and acceptability of the items, scaling
assumpt ions, reliabilit y, precision and validit y. 11 We will
briely explain below what these metric properties are
comprised of.
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340
Accept abilit y is t he met ric propert y t hat analyses if
t he dist ribut ion of t he scores in a scale represent s t he real
dist ribut ion of t he st at e of healt h or disease of t he sample.
Accept abilit y was assessed t hrough dist ribut ion analysis and
a score range, scores observed vs possible LLAMSQ values
and loor and ceiling effects. The last terms refer to the
percent age of individuals t hat score in ext reme LLAMSQ
values (minimum and maximum score obt ained respect ively,
which should be less t han 15%). 12
Scaling assumpt ions refer t o checking t he correct grouping
of t he it ems in t he LLAMSQ. They also assess if t he sum of
t he 5 it ems is appropriat e t o produce t he t ot al score of t he
const ruct “ suffering from acut e mount ain sickness,” which
we are t rying t o measure. Scaling assumpt ions are checked
via t he t ot al correct ed it em-score correlat ion, avoiding t he
inclusion of t he it em it self in t he t ot al. The t ot al correct ed
LLAMSQ item-score should be greater than or equal to 0.3013
(Spearman’s correlation coeficient).
Reliability is the property indicating that the questionnaire
is free from random error. Int ernal consist ency, t oget her
wit h reproducibilit y, is a fundament al feat ure of t his met ric
at t ribut e. The int ernal consist ency of LLAMSQ was assessed
using Cronbach’s alpha. An accept able int ernal consist ency
was considered as values above 0.7. 14
Precision refers to the ability of the questionnaire to
det ect small differences. This met ric at t ribut e is expressed
in a st andard measurement error form, which is calculat ed
wit h t he following formula: st andard error of t he
measurement=standard
deviation
x
√(1-reliability
coeficient).15
The validit y of t he ext ernal const ruct refers t o t he
combinat ion of st rat egies used t o est ablish validit y of a
measurement inst rument t hrough a series of procedures
t hat analyse t he relat ionship of t he score obt ained wit h
ot her similar ones. For t his, convergent validit y and
discriminat ive validit y have t o be det ermined at t he same
t ime. 16
Convergent validit y is t he level t o which a scale correlat es
wit h t he result s obt ained wit h ot her measurement s for t he
same const ruct . 17 For t his, we calculat ed Spearman’s
correlation coeficient (rS) bet ween t he mean LLAMSQ score
wit h a set of self-report ing it ems creat ed by t he aut hors
(t able 4: Ment al sympt oms, at axia, dyspnoea and t remor),
which were assessed at t he same t ime as t he acut e mount ain
sickness scale was applied. The a priori hypot heses
est ablished was t hat t hese correlat ions wit h t he neurological
self-examining it ems would be moderat e (r S=0.30–0.59).
Discriminat ive validit y refers t o t he capacit y of t he
measurement inst rument (LLAMSQ) t o det ect differences at
a point in t ime bet ween groups t hat are different in ot her
measurement s. Discriminat ive validit y was assessed
calculat ing t he mean LLAMSQ score bet ween t hose
neurologist s who t hought t hey had present ed acut e
mount ain sickness against t hose who report ed not having
had it. The 2 questions used were the following: Do you
t hink you have suffered from acut e mount ain sickness? Do
you t hink you have part ially suffered from acut e mount ain
sickness? The mean scores obt ained in t he LLAMSQ in bot h
groups were compared using t he Mann-Whit ney U t est .
The st at ist ical analysis was carried out using t he SPSS
13.0 programme (SPSS, Chicago, IL).
F.J. Carod-Art al et al
Table 4 Ext ernal clinical assessment it ems used t o
measure t he convergent validit y of t he self-report ing Lake
Louise Acut e Mount ain Sickness Quest ionnaire
Ment al sympt oms
None
Mild at t ent ion disorder, slight slowness
in t hinking
Moderate bradypsychia, frequent disorientation
Inabilit y t o ret ain informat ion, confusion,
hallucinat ions
At axia
None
Mild, wit h an occasional st umble or manual
clumsiness
Moderat e, wit h obvious clumsiness in walking
or when using hands
Serious, needs help t o walk or eat
Dyspnoea
No respiratory dificulty
Dyspnoea wit h moderat e exercise (going up a
hill)
Dyspnoea wit h slight exercise (walking on t he
level)
Rest ing dyspnoea
Tremor
None
Slight tremor (makes signing dificult
or condit ions it )
Moderate tremor (makes using cutlery dificult)
Serious t remor (incapacit at ing)
0
1
2
3
0
1
2
3
0
1
2
3
0
1
2
3
Results
Sevent y Caucasian Spanish people, who had not previously
lived in geographical regions of alt it ude, t ook part in t he
st udy. The mean alt it ude t hey normally lived at was 409.7m
above sea level. There was a percent age of 60% who were
male, a mean age of 50±8 years and 88.6%of t he part icipant s
were neurologist s. Their mean weight was 74.4±15.2kg and
mean height was 170.3±8.7cm. There was a 31%percent age
rat e of part icipant s who present ed migraine and 15.7%
smoked. There were no people who had act ive or
sympt omat ic pulmonary disease.
The questionnaire was carried out after the course had
inished. Of the subjects, 16% recognised having suffered
from acut e mount ain sickness and 36.2%a part ial form of it .
The irst 2 days of the course took place in Lima, at sea
level. The st ay in alt it ude over t he next days was as follows:
Cuzco (2 days and 2 night s), 3,400 met res above sea level
(MASL); Valle Sagrado (a day and a night ), 2,850 MASL; and
Machu Picchu (a day), 2,450 MASL. The physical act ivit y
carried out during t he st ay on t he neurological hist ory
course was moderat e, t he part icipant s did not undert ake
mount ain crossings and t hey had no previous exposure t o
moderat e or high alt it udes.
The LLAMSQ mean score was 3.36±2.02 (median, 3;
skewness, 0.61). The range of values observed swung from
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Met ric propert ies of t he Spanish version of t he Lake Louise Acut e Mount ain Sickness Quest ionnaire
0 to 10 (possible range: 0-15). The loor and ceiling effects
were 7.3 and 1.4%respect ively.
The correct ed it em-t ot al correlat ion (Spearman
coeficient) was: 0.27 (sleep item), 0.33 (dizziness item),
0.34 (nausea it em), 0.39 (headache it em) and 0.57 (t iredness
it em). The Cronbach alpha score was 0.61 and t he st andard
error of t he measurement , 1.26. The eliminat ion of it em 5
(sleep) improved t he Cronbach alpha score by 0.63.
Wit h relat ion t o t he convergent validit y, t he LLAMSQ
correlated signiicantly with the items of physical selfexaminat ion: at axia, dyspnoea, t remor and ment al
symptoms (r=0.41; P=0.002). The correlation between the
dyspnoea and tiredness items was signiicant (r=0.39).
The discriminat ive validit y was appropriat e. The scores
obtained in the LLAMSQ were signiicantly greater (worse)
in t he group of neurologist s t hat responded having suffered
from acut e mount ain sickness (5.8 point s vs 3.0 point s;
Mann-Whit ney U, P<0.0001).
Discussion
We present t he met ric propert ies of t he Spanish LLAMSQ
version. The aut hors have not found a psychomet ric analysis
process and st andardised validat ion in medical lit erat ure,
in accordance t o t he modern psychomet ric t heories, of t he
original English version. The LLAMSQ adapt at ion was carried
out in a group of neurologist s exposed t o alt it ude wit h no
previous acclimat isat ion. The sample could be represent at ive
of a group of middle-aged individuals who t ravel t o areas of
high alt it ude wit h no previous acclimat isat ion and not for
sport ing reasons. The applicat ion of LLAMSQ in children and
adolescent s can underest imat e t he sympt oms of acut e
mount ain sickness. 18
The percent age of scores in t he ext reme values of t he
scale (loor and ceiling effects) was small in LLAMSQ. There
were no high values in t he scale because t here were no
serious cases of acut e mount ain sickness and t here was
no exposure t o alt it udes of more t han 4,000m.
The int ernal consist ency found, according t o Cronbach’s
alpha, was moderat e (0.63). This is part ly explained because
t he value of Cronbach’s alpha is dependent on a number of
it ems comprising a scale and decrease as t heir number in
t he scale or cat egory is reduced. In a st udy of miners who
were exposed t o alt it ude in Chile, t he Cronbach alpha value
of LLAMSQ was 0.70. 19
The scaling assumpt ions of t he it ems were suit able and
only t he sleep it em scored under 0.30. The t iredness it em
presented the best item-questionnaire correlation. The fact
t hat it was a middle aged populat ion, who did not pract ise
physical act ivit ies regularly at high alt it ude, could have
inluenced the result. However, tiredness can be a sensitive
clinical symptom that is frequently associated to acute
mount ain sickness. An import ant fact of t he score syst em is
t hat it emphasises t he import ance of headache in t he
deinition of acute mountain sickness. The item-total
correlat ion for t he headache it em was great er t han t he
crit eria est ablished (0.39).
The st andard error of t he measurement was small.
Theref ore, t he dif f erence in a point t hat could be obt ained
f rom t wo dif f erent measurement s on t he scale could be
341
due to the error of measurement from the questionnaire
it self .
The LLAMSQ t est also has suit able discriminat ive validit y,
given t hat t he scores obt ained show t hat t he individuals in
t he sample who present ed acut e mount ain sickness
symptoms scored worse in this questionnaire. The convergent
validit y of t he Spanish version of LLAMSQ seems t o be
equally correct.
However, t his st udy present s some limit at ions. It was
carried out among middle-aged people who were exposed
t o alt it ude wit hout previous acclimat isat ion, t he maj orit y
of whom were neurologist s; t his is why t he generalisat ion of
the indings for other population groups could be limited.
The analysis for convergent validit y wit h t he it ems of selfreport ing physical examinat ion might not be ext rapolat ive,
as it deals wit h a t rained sample, and t he clinical assessment
was carried out by t he neurologist s t hemselves subj ect t o
t he t rial. Despit e being able t o assess whet her t hey
present ed sympt oms of acut e mount ain sickness, an ext ernal
clinical assessment t o est ablish t he diagnosis of acut e
mount ain sickness would have been advisable. As t he
acut e mount ain sickness sympt oms were not very severe,
no self-report ing variables were used, such as t he percent age
of oxygen sat urat ion and t he presence of cyanosis, for
example. However, t he analysis of known groups suggest s
t he validit y of t he scale.
The variabilit y of t he dat a obt ained in our sample is
limit ed, as t he maj orit y of t he individuals scored in t he
lower t wo t hirds of t he scale. This is probably due t o t he
fact t hat t he exposure t o alt it ude was moderat e. This fact
could hinder t he assessment of t he behaviour of t he scale in
individuals present ing more int ense acut e mount ain
sickness. However, t he people in our st udy went from sea
level alt it ude t o an alt it ude of more t han 3,500m wit hout
any previous acclimat isat ion. We believe t hat t his change in
alt it ude is indeed of value, mainly because t he scale is
direct ed at people who oft en expose t hemselves t o a
medium alt it ude wit hout acclimat isat ion and not t o an
ext reme alt it ude.
This st udy suggest s t hat t he Spanish version of LLAMSQ
could be a suitable questionnaire to assess the symptoms of
acut e mount ain sickness. The populat ion in which t he
metric properties were assessed in the questionnaire was
mainly composed of neurologist s. This is why we recommend
new psychomet ric st udies t hat can analyse ot her met ric
propert ies (reproducibilit y, sensit ivit y t o change), as well
as t heir applicat ion t o ot her select ed reference groups
(sport ent husiast s, mount aineers, young people and t he
elderly) by combining t he use of ot her inst rument s t o assess
acut e mount ain sickness. 20, 21 In t his t ype of st udies, an
ext ernal clinical examinat ion for acut e mount ain sickness is
recommended so as t o be able t o analyse sensit ivit y and
speciicity. To conclude, the metric properties of LLAMSQ
seem to be suitable. This self-reporting questionnaire could
be useful for t he early det ect ion of acut e mount ain
sickness.
Conlict of interest
The authors have no conlict of interest to declare.
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342
Acknowledgements
We are grat eful t o all t he people who t ook part in t he
neurological hist ory course “ Neuroscience in Pre-Columbian
Andean Cult ures” held in Peru in 2009.
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