Este documento presenta un estudio observacional que comparó pacientes con infarto agudo de miocardio (casos) con sujetos sanos (controles) para determinar si la exposición al oxígeno terapéutico se asociaba con mejores resultados. El estudio encontró que los pacientes expuestos al oxígeno tuvieron menos complicaciones que aquellos no expuestos, lo que sugiere que el oxígeno terapéutico podría ser beneficioso para pacientes con infarto agudo de miocardio.
1. Oxygen therapy for acute myocardial infarction (
Cabello JB, Burls A, Emparanza JI, Bayliss S, Quinn T
práctica
basada en
evidencia
This is a reprint of a Cochrane review, prepared and maintained by The Cochrane Collaboration and published
de la investigación a la toma de decisiones en salud
2010, Issue 6
http://www.thecochranelibrary.com
4. ¿Qué significa?
a. El 20% de la gente que come tocino tendrá cáncer colorrectal alguna
vez en su vida
b. El 20% de los cánceres colorrectales son producidos por haber comido
tocino
c. 1 de cada100 personas que come tocino, tendrá cáncer de colon por
esta causa.
d. Si como tocino, tengo un 20% (cada año) de probabilidades de tener
cáncer colorrectal.
e. Mi riesgo basal de cáncer colorrectal, se incrementa un 20% por comer
tocino.
5. Los pasos de la Medicina Basada en Evidencia
P Preguntar
I Indagar/buscar
L Leer críticamente
A Aplicar
R Repasar
32. EARLY REPORT
Early report
Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and
pervasive developmental disorder in children
A J Wakefield, S H Murch, A Anthony, J Linnell, D M Casson, M Malik, M Berelowitz, A P Dhillon, M A Thomson,
P Harvey, A Valentine, S E Davies, J A Walker-Smith
Summary Introduction
We saw several children who, after a period of apparent
Background We investigated a consecutive series of
normality, lost acquired skills, including communication.
children with chronic enterocolitis and regressive
They all had gastrointestinal symptoms, including
developmental disorder.
abdominal pain, diarrhoea, and bloating and, in some
Methods 12 children (mean age 6 years [range 3–10], 11 cases, food intolerance. We describe the clinical findings,
boys) were referred to a paediatric gastroenterology unit and gastrointestinal features of these children.
with a history of normal development followed by loss of
acquired skills, including language, together with diarrhoea Patients and methods
and abdominal pain. Children underwent 12 children, consecutively referred to the department of
paediatric gastroenterology with a history of a pervasive
gastroenterological, neurological, and developmental
developmental disorder with loss of acquired skills and intestinal
assessment and review of developmental records. symptoms (diarrhoea, abdominal pain, bloating and food
Ileocolonoscopy and biopsy sampling, magnetic-resonance intolerance), were investigated. All children were admitted to the
imaging (MRI), electroencephalography (EEG), and lumbar ward for 1 week, accompanied by their parents.
puncture were done under sedation. Barium follow-through
radiography was done where possible. Biochemical, Clinical investigations
haematological, and immunological profiles were We took histories, including details of immunisations and
exposure to infectious diseases, and assessed the children. In 11
examined.
cases the history was obtained by the senior clinician (JW-S).
Findings Onset of behavioural symptoms was associated, Neurological and psychiatric assessments were done by
consultant staff (PH, MB) with HMS-4 criteria.1 Developmental
by the parents, with measles, mumps, and rubella
histories included a review of prospective developmental records
vaccination in eight of the 12 children, with measles from parents, health visitors, and general practitioners. Four
infection in one child, and otitis media in another. All 12 children did not undergo psychiatric assessment in hospital; all
children had intestinal abnormalities, ranging from had been assessed professionally elsewhere, so these assessments
lymphoid nodular hyperplasia to aphthoid ulceration. were used as the basis for their behavioural diagnosis.
Histology showed patchy chronic inflammation in the colon After bowel preparation, ileocolonoscopy was performed by
SHM or MAT under sedation with midazolam and pethidine.
in 11 children and reactive ileal lymphoid hyperplasia in
Paired frozen and formalin-fixed mucosal biopsy samples were
seven, but no granulomas. Behavioural disorders included taken from the terminal ileum; ascending, transverse,
autism (nine), disintegrative psychosis (one), and possible descending, and sigmoid colons, and from the rectum. The
postviral or vaccinal encephalitis (two). There were no procedure was recorded by video or still images, and were
focal neurological abnormalities and MRI and EEG tests compared with images of the previous seven consecutive
were normal. Abnormal laboratory results were significantly paediatric colonoscopies (four normal colonoscopies and three
on children with ulcerative colitis), in which the physician
raised urinary methylmalonic acid compared with age- reported normal appearances in the terminal ileum. Barium
matched controls (p=0·003), low haemoglobin in four follow-through radiography was possible in some cases.
children, and a low serum IgA in four children. Also under sedation, cerebral magnetic-resonance imaging
(MRI), electroencephalography (EEG) including visual, brain
Interpretation We identified associated gastrointestinal stem auditory, and sensory evoked potentials (where compliance
disease and developmental regression in a group of made these possible), and lumbar puncture were done.
previously normal children, which was generally associated
in time with possible environmental triggers. Laboratory investigations
Thyroid function, serum long-chain fatty acids, and
Lancet 1998; 351: 637–41 cerebrospinal-fluid lactate were measured to exclude known
See Commentary page causes of childhood neurodegenerative disease. Urinary
methylmalonic acid was measured in random urine samples from
Inflammatory Bowel Disease Study Group, University Departments eight of the 12 children and 14 age-matched and sex-matched
of Medicine and Histopathology (A J Wakefield FRCS, A Anthony MB, normal controls, by a modification of a technique described
J Linnell PhD, A P Dhillon MRCPath, S E Davies MRCPath) and the previously.2 Chromatograms were scanned digitally on
University Departments of Paediatric Gastroenterology computer, to analyse the methylmalonic-acid zones from cases
(S H Murch MB, D M Casson MRCP, M Malik MRCP, and controls. Urinary methylmalonic-acid concentrations in
M A Thomson FRCP, J A Walker-Smith FRCP,), Child and Adolescent patients and controls were compared by a two-sample t test.
Psychiatry (M Berelowitz FRCPsych), Neurology (P Harvey FRCP), and Urinary creatinine was estimated by routine spectrophotometric
Radiology (A Valentine FRCR), Royal Free Hospital and School of assay.
Medicine, London NW3 2QG, UK Children were screened for antiendomyseal antibodies and
Correspondence to: Dr A J Wakefield boys were screened for fragile-X if this had not been done
THE LANCET • Vol 351 • February 28, 1998 637
33.
34. EARLY REPORT
Early report
Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and
pervasive developmental disorder in children
A J Wakefield, S H Murch, A Anthony, J Linnell, D M Casson, M Malik, M Berelowitz, A P Dhillon, M A Thomson,
P Harvey, A Valentine, S E Davies, J A Walker-Smith
Summary Introduction
We saw several children who, after a period of apparent
Background We investigated a consecutive series of
normality, lost acquired skills, including communication.
children with chronic enterocolitis and regressive
They all had gastrointestinal symptoms, including
D
developmental disorder.
abdominal pain, diarrhoea, and bloating and, in some
Methods 12 children (mean age 6 years [range 3–10], 11 cases, food intolerance. We describe the clinical findings,
boys) were referred to a paediatric gastroenterology unit and gastrointestinal features of these children.
with a history of normal development followed by loss of
acquired skills, including language, together with diarrhoea Patients and methods
E
and abdominal pain. Children underwent 12 children, consecutively referred to the department of
paediatric gastroenterology with a history of a pervasive
gastroenterological, neurological, and developmental
developmental disorder with loss of acquired skills and intestinal
assessment and review of developmental records. symptoms (diarrhoea, abdominal pain, bloating and food
Ileocolonoscopy and biopsy sampling, magnetic-resonance intolerance), were investigated. All children were admitted to the
T
imaging (MRI), electroencephalography (EEG), and lumbar ward for 1 week, accompanied by their parents.
puncture were done under sedation. Barium follow-through
radiography was done where possible. Biochemical, Clinical investigations
haematological, and immunological profiles were We took histories, including details of immunisations and
C
exposure to infectious diseases, and assessed the children. In 11
examined.
cases the history was obtained by the senior clinician (JW-S).
Findings Onset of behavioural symptoms was associated, Neurological and psychiatric assessments were done by
consultant staff (PH, MB) with HMS-4 criteria.1 Developmental
by the parents, with measles, mumps, and rubella
histories included a review of prospective developmental records
vaccination in eight of the 12 children, with measles
A
from parents, health visitors, and general practitioners. Four
infection in one child, and otitis media in another. All 12 children did not undergo psychiatric assessment in hospital; all
children had intestinal abnormalities, ranging from had been assessed professionally elsewhere, so these assessments
lymphoid nodular hyperplasia to aphthoid ulceration. were used as the basis for their behavioural diagnosis.
Histology showed patchy chronic inflammation in the colon After bowel preparation, ileocolonoscopy was performed by
SHM or MAT under sedation with midazolam and pethidine.
R
in 11 children and reactive ileal lymphoid hyperplasia in
seven, but no granulomas. Behavioural disorders included
autism (nine), disintegrative psychosis (one), and possible
postviral or vaccinal encephalitis (two). There were no
Paired frozen and formalin-fixed mucosal biopsy samples were
taken from the terminal ileum; ascending, transverse,
descending, and sigmoid colons, and from the rectum. The
procedure was recorded by video or still images, and were
compared with images of the previous seven consecutive
focal neurological abnormalities and MRI and EEG tests
T
were normal. Abnormal laboratory results were significantly paediatric colonoscopies (four normal colonoscopies and three
on children with ulcerative colitis), in which the physician
raised urinary methylmalonic acid compared with age- reported normal appearances in the terminal ileum. Barium
matched controls (p=0·003), low haemoglobin in four follow-through radiography was possible in some cases.
children, and a low serum IgA in four children. Also under sedation, cerebral magnetic-resonance imaging
E
(MRI), electroencephalography (EEG) including visual, brain
Interpretation We identified associated gastrointestinal stem auditory, and sensory evoked potentials (where compliance
disease and developmental regression in a group of made these possible), and lumbar puncture were done.
previously normal children, which was generally associated
Laboratory investigations
R
in time with possible environmental triggers.
Thyroid function, serum long-chain fatty acids, and
Lancet 1998; 351: 637–41 cerebrospinal-fluid lactate were measured to exclude known
See Commentary page causes of childhood neurodegenerative disease. Urinary
methylmalonic acid was measured in random urine samples from
Inflammatory Bowel Disease Study Group, University Departments eight of the 12 children and 14 age-matched and sex-matched
of Medicine and Histopathology (A J Wakefield FRCS, A Anthony MB, normal controls, by a modification of a technique described
J Linnell PhD, A P Dhillon MRCPath, S E Davies MRCPath) and the previously.2 Chromatograms were scanned digitally on
University Departments of Paediatric Gastroenterology computer, to analyse the methylmalonic-acid zones from cases
(S H Murch MB, D M Casson MRCP, M Malik MRCP, and controls. Urinary methylmalonic-acid concentrations in
M A Thomson FRCP, J A Walker-Smith FRCP,), Child and Adolescent patients and controls were compared by a two-sample t test.
Psychiatry (M Berelowitz FRCPsych), Neurology (P Harvey FRCP), and Urinary creatinine was estimated by routine spectrophotometric
Radiology (A Valentine FRCR), Royal Free Hospital and School of assay.
Medicine, London NW3 2QG, UK Children were screened for antiendomyseal antibodies and
Correspondence to: Dr A J Wakefield boys were screened for fragile-X if this had not been done
THE LANCET • Vol 351 • February 28, 1998 637
40. P
Mujeres
embarazadas
IóE A C
Fumar Fumar
¿mediante un ECA? Cigarrillos Placebo
• No ético
T
O +
Parto
pretérmino
-
41. P
Mujeres
embarazadas
E C
Fuma
Cohorte cigarrillos No fuma
• ¿Ético?
T
O +
Parto
pretérmino
-
42. Evalúan la
exposición o no
exposición
E C
Fumó
Casos y controles Cigarrillos No fumó
T
P O +
Mujeres Parto
pretérmino
elegibles
-
Grupos con y sin
desenlace
43. Revisión sistemática Síntesis
Ensayo clínico aleatorio Experimental
Analíticos
cohorte
casos y controles
Observacional
Transversales
S e s g o
(cross-sectional)
Descriptivos
Observaciones clínicas
(serie de casos, reporte de un
caso)
Recomendaciones de
experto
51. Para que haya asociación válida y pensar en
causalidad, hay que evaluar...
• El sesgo
• Factores de confusión
• El papel del azar
52. Sesgos
• Sesgos de selección
• Berksonian
• Sesgo del respondedor (response bias)
• Sesgos de información
• Sesgo de clasificación (missclassification bias)
• Sesgo de recuerdo (recall bias)
• Sesgo de reporte (reporting bias)
• Sesgo de detección (surveillance bias)
53. Sesgos
• Sesgos de selección
• Berksonian - cuando se usa la frecuencia de admisiones hospitalarias; son
distintas para los que tienen enfermedad que en los controles
• Sesgo del respondedor (response bias) - aquellos que aceptan entrar a un
estudio son distintos a los que no (voluntarios son distintos)
• ... El autor determina los criterios de elección y los aplica diferente en los
casos que en los controles
54. Sesgos
• Sesgos de información
• Sesgo de clasificación (missclassification bias)
- mal clasifican los casos y los controles por indagar más al momento de
ingresarlos al estudio, p. ej., casos de TDAH vs controles, al momento de
evaluar si los controles son o no TDAH, puede que a ellos no se les haga
las preguntas más a fondo o no se hagan pruebas de detección.
• Sesgo de recuerdo (recall bias)
- Mujeres que tuvieron aborto pueden recordar más que estuvieron
expuestas a campos magnéticos de antenas, que aquellas (controles)
que no tuvieron un aborto.
55. Sesgos
• Sesgos de información
• Sesgo de reporte (reporting bias)
- Los casos no reportan ciertas actitudes o problemas; p. ej., los adictos
pueden no decir que consumieron drogas
• Sesgo de detección (surveillance, ascertainment bias)
- mujeres que toman la píldora tendrán más exámenes pap = más cáncer
se detecta en ellas. Al momento de hacer un casos-controles, los
casos (cáncer) habrán tomado más píldoras y se creerá que las
píldoras producen cáncer.
56. Channeling effect (tiro por la culata)
• Acto #1: se crea el ketoprofeno
• Acto #2: los creadores dicen que produce menos sangrado gastrointestinal
(SGI) y así lo promocionan
• Acto #3: los doctores se lo dan a los pacientes con alto riesgo de sangrar
(claro, porque produce menos sangrados)
• Resultado: posteriormente, al hacer un estudio de cohorte o casos-controles,
los resultados dicen que los pacientes que toman ketoprofeno, sangran más
que los que toman otros AINEs
62. 4 casas pérdida x casa camiones usados
$
100,000
1,000,000
63. CONCLUSIONES
• Entre más camiones de
bomberos se usen, más
dinero se pierde.
• Es necesario reducir el
número de camiones en
los incendios
64. Asociación no siempre es causalidad
• La vacuna MMR produce autismo
• Adenovirus causa obesidad
• Los divorcios son producidos por el incremento de los precios de la cerveza
• Tamaño del zapato e inteligencia
• Tomar café es malo para la salud
• Niños que desayunan son más sanos e inteligentes
73. tercer ronda
No es justo,
el promedio
de LARGO
DEL
CABELLO Es necesario
era mayor en ajustar...
las mujeres,
eso influye
en el
resultado
final ¡Un momento...!
76. P
Mujeres
embarazadas
E C
Fuma
Cohorte cigarrillos
No fuma
n=251 n=1992
• resultados
T
• OR=3.2 (1.42 a 7.23)
O + 25 88
Parto
pretérmino
- 226 1904
81. Odds vs probabilidad
Pastel de reyes con un muñeco escondido dentro
del mismo.
Partido en cuatro partes
Si tomas un pedazo...
¿Qué probabilidad hay de sacar el muñeco?
86. P
0.11 Mujeres
Odds de parto embarazadas
pretérmino en
grupo de E C
exposición Fuma
No fuma
cigarrillos
n=251 n=1992
T
O + 25 88
Odds de parto
Parto
pretérmino en pretérmino
grupo control - 226 1904
0.04
OR crudo = 2.7
87. IC 95%
P
Mujeres
embarazadas
0.1 0.5 0.7 1 2 3 5 7
E C
Fuma
No fuma
cigarrillos
n=251 n=1992
• resultados
T
• OR=3.2 (1.42 a 7.23)
O + 25 88
Parto
pretérmino
- 226 1904
89. ¿Qué significa?
a. El 20% de la gente que come tocino tendrá cáncer colorrectal alguna
vez en su vida
b. El 20% de los cánceres colorrectales son producidos por haber comido
tocino
c. 1 de cada100 personas que come tocino, tendrá cáncer de colon por
esta causa.
d. Si como tocino, tengo un 20% (cada año) de probabilidades de tener
cáncer colorrectal.
e. Mi riesgo basal de cáncer colorrectal, se incrementa un 20% por comer
tocino.