[Attention deficit hyperactivity disorder in adults]. / Trastorno por déficit de atención/hiperactividad en adultos.

INTRODUCTION AND DEVELOPMENT: Attention deficit hyperactivity disorder (ADHD) may exist in up to 60% of adults, whose first symptoms appeared before they were seven years old. Since it is a neurobiological condition, its basic symptoms -lack of attention, hyperactivity and impulsiveness- are similar at all ages, but in adults the clinical manifestations are specific to the subgroup with more frequent comorbidities than in childhood. Manifestations that characteristically appear in adults are difficulty in concentrating, poorer memory and short-term memory, disorganisation, difficulties with self-discipline, impulsiveness, low self-esteem, mental restlessness, frustration and limited social skills. CONCLUSIONS: Today, adult cases are underdiagnosed because for a long time ADHD was thought to be a condition that only affected children and teenagers; however, although its clinical manifestations in adults are essentially similar to those seen in children, they are different and have different forms of presentation. There are no biomedical tests that allow an objective diagnosis to be established, and thus care must be taken to draw up and evaluate a patient record that includes possible symptoms since childhood, typical signs and symptoms, and any relevant comorbidities. Self-evaluation scales are necessary as the preferred instrument for use as an aid to the patient record. The main pharmacological treatment is based on psychopharmaceuticals such as immediate-, controlled- or extended-release methylphenidate and on atomoxetine; cognitive-behavioural and psychosocial treatment should also be associated.

[Cognitive functions and neuronal networks in the social brain]. / Funciones cognitivas y redes neuronales del cerebro social.

INTRODUCTION AND DEVELOPMENT: The brain is the organ that contains the structures that are needed to establish and maintain relationships, which is the basis for the survival of the individual and the species as a whole. It is so important that the destruction of any of the structures involved can give rise to situations that are irreparable today and prevent correct sociability. Pathologies such as autism spectrum disorders, schizophrenia, bipolar disorders, obsessive-compulsive disorder and attention deficit hyperactivity disorder are conditions that trigger dysfunctions in the individual with respect to the environment. CONCLUSIONS: In each of these pathologies one or several neuronal networks/regions may be compromised and this impedes connectivity between those that constitute the social brain.

[Clinical variability and characteristics of attention deficit hyperactivity disorder in girls]. / Características y variabilidad clínica del trastorno por déficit de atención/hiperactividad en niñas.

INTRODUCTION: Attention deficit hyperactivity disorder (ADHD) is a neurobiological condition essentially characterised by inattention, hyperactivity and impulsiveness, and has a prevalence of around 5%. Because it is a biological disorder, both boys and girls with ADHD display these same symptoms, but more boys are diagnosed with ADHD (in a ratio of 3 to 1). AIM: To examine the differences between the two sexes, their prevalence and possible female subtypes in ADHD. PATIENTS AND METHODS: We conducted a retrospective study of 172 patients of both sexes who were attended as hospital neuropaediatric outpatients in the year 2004 according to Diagnostic and statistical manual of mental disorders (DSM-IV-TR) criteria. Their ages ranged between 4 and 14 years and they were divided into three groups: under 6, between 6 and 10, and from 11 to 14 years old. The girls were subdivided into four subtypes, in order of greater to lesser prevalence: shy, hypersociable, hyperactive and changeable. RESULTS: Both sexes showed the same response to methylphenidate. Only the group of boys presented other comorbidities such as negativism and conduct disorders; approximately 25% of them required treatment with atypical neuroleptic drugs. CONCLUSIONS: a) Girls have certain specific clinical manifestations within the three common symptoms; b) methylphenidate is equally effective in both sexes; c) only boys display other disorders such as negativism and conduct disorders; and d) the brains of males and females are quite similar, but symptoms are expressed differently depending on environments and levels.

[Best practice guidelines for the diagnosis of autistic spectrum disorders]. / Guía de buena práctica para el diagnóstico de los trastornos del espectro autista.

INTRODUCTION: The autism spectrum disorder (ASD) diagnostic process requires expertise both in the knowledge of autism as in teamwork strategies with different professionals, often working in different clinic services, and with parents. AIM: To recommend a consensus diagnostic procedure for ASD, that has been designed by the Study Group of the Instituto de Salud Carlos III. DEVELOPMENT: The reports emphasize the need to obtain a complete clinical history, covering personal, family and psychosocial antecedents; detailing the basic areas affected in ASD--social interaction, communication and restricted patterns of behaviour, activities and interests. Diagnostic tests to be used as a routine in all cases are described and analysed--including both psychoeducational and biomedical tests. Also, tests indicated in cases with suspected identifiable physical disorders are covered, as well as those medical tests to be used for research purposes only. CONCLUSION: The diagnostic procedure requires the implementation of a coordinated interdisciplinary assessment strategy, that needs to ensure the participation of professionals from very different fields in active collaboration with the family. Their role culminates in the preparation and delivery of a personalized report. Every diagnostic procedure needs to be accompanied by an action plan that includes immediate support to the person with ASD, as well as information to the family on resources and community initiatives in their living area.

[Best practice guidelines for research in autistic spectrum disorders]. / Guía de buena práctica para la investigación de los trastornos del espectro autista.

INTRODUCTION: Achieving a better knowledge of autism and other pervasive developmental disorders known as autistic spectrum disorders (ASD), poses a major scientific challenge. These disorders are some of the earliest and most severe psychopathological disorders in infancy; they include an heterogeneous group of conditions; its prevalence rate seems to be continually increasing and they generate a significant social impact. AIMS AND DEVELOPMENT: Nowadays, there is a current international agreement on the general requirements to be fulfilled by research projects and the priority areas to be considered when developing ASD high quality research. In Spain, although there are some established research groups with broad experience and expertise in these disorders, public funding opportunities and research development are still scarce. For this reason, the Study Group of the Instituto de Salud Carlos III has generated by consensus some Good Practice Guidelines for Research in ASD. CONCLUSIONS: After comparing priorities and recommendations from international reference documents with the results obtained after having carried out an exhaustive bibliographic revision of articles published in autism in the last 30 years by Spanish authors, methodological and ethical recommendations are established. Finally, structural deficiencies to be corrected and emerging research initiatives to be supported are identified.

[Best practice guidelines for the early detection of Autistic Spectrum Disorders (I)]. / Guía de buena práctica para la detección temprana de los trastornos del espectro autista (I).

INTRODUCTION: The interest in early detection of Autism Spectrum Disorders (ASD) lies in the accumulated evidence of the fact that an early customized intervention for children with an ASD and their families leads to an improvement of the child's prognosis in most cases. OBJECTIVE: To establish criteria and procedures for early identification of children at risk of ASD and to facilitate full diagnostic assessment and prompt referral leading to adequate support. Early detection of ASD is extremely important, since early specific individualized treatment for the child and his or her family leads to long-term improvement in many children' prognosis. DEVELOPMENT: Firstly, a critical appraisal of the situation of early detection of ASD in Spain is made after reviewing the scarce bibliography available on current screening and diagnostic practices in the country. Data generated by questionnaires received from 646 Spanish families is also taken into account. Secondly, the Study Group of the Instituto de Salud Carlos III recommends the screening and early diagnosis process to be followed, describing the necessary steps, the public services involved and the available screening and diagnostic tools. CONCLUSIONS: The Study Group draws the main conclusions regarding the situation of ASD early detection in Spain, and makes a consensus proposal for the detection procedures, including routine developmental surveillance and identification of children at risk for ASD by using sensitive and specific assessment tools.

[Cognitive evoked potentials in face recognition in autism]. / Potenciales evocados cognitivos en el reconocimiento de caras en el autismo.

INTRODUCTION AND DEVELOPMENT: Face recognition requires a special type of processing that is different to that used to recognise objects. The right medial region of the fusiform gyrus displays a higher degree of activation when dealing with faces, which is why it is known as the fusiform face area, although the integrity of the right occipital face area may be needed to perform this task. Neuroimaging studies point not only to the existence of normal activation of the fusiform face area in response to faces but also of the occipital area. One modulation that supports the existence of a specific pathway is the face inversion effect, which is defined as the process in which greater disability is displayed in the recognition of inverted faces than for other mono-oriented objects. The P1 potential is the initial endogenic component of visual processing, acting as an index of the processing of features that show lower latency and greater amplitude when dealing with a face stimulus than when stimulated by objects. A later response, the negative component N170, also has lower latency in the case of faces than in inversion and objects. Its amplitude increases when the faces are inverted due to the generation of a greater activation in the region where it originates. A later negative potential can be associated to semantic identification in face recognition. The N170 waves in autistic individuals display greater latency with faces that is similar to the response to objects and, in turn, show no differences in the latencies with inverted faces. It remains to be shown whether they have an N400 response to faces. CONCLUSIONS: Cognitive evoked potentials allow us to evaluate face recognition both in normal and autistic individuals by presenting responses to specific stimuli. Further studies will enable us to determine whether an N400 response exists in individuals with autism.

[The diagnostic evaluation and therapeutic basis of immediate release methylphenidate in attention deficit hyperactivity disorder]. / Evaluacion diagnostica y bases terapeuticas del metilfenidato de liberacion inmediata en el trastorno por deficit de atencion con hiperactividad.

INTRODUCTION: Attention deficit disorder with or without hyperactivity (ADHD) is characterised by the patients' inability to pay attention in non selective activities, hyperactivity that is difficult to inhibit, impulsiveness with failure to control their reactions and an unstable personality, which gives rise to difficulties in learning, work, leisure activities and in the social milieu, and may get worse in unstructured settings. There is a clear predominance in males and a 57% possibility of inheritance. The biochemical causes underlying ADHD are unknown, although it is currently accepted that dopamine and noradrenaline release is reduced because of the positive response to methylphenidate (MPH) and other stimulants. AIMS: The aim of this study was to evaluate the response to immediate release MPH by combining clinical data based on the DSM IV and brain mapping and quantitative electroencephalogram studies (qEEG). PATIENTS AND METHODS: We conducted a study of 170 otherwise pathology free children with a 5 to 1 predominance of males and an average age of 8 years old. Patients' records were examined and a hemogram and general biochemical analysis were carried out together with tests to determine thyroid hormone and cortisol levels, and BM CEEG. In addition, 46 children were submitted to a nocturnal polysomnogram (nPSG). RESULTS: A third of the children presented associated pathologies such as allergic rhinitis, asthma, allergies and dermatitis, with no differences between sexes. Paroxysmal discharges were revealed by the nPSG in 16.7% and there was a general agreement between answers provided by families and teachers. In the qEEG the most striking data was the theta/alpha quotient, which showed a medium degree of generalised dominance of the theta band (but no correlation with age) in 49.9% and it was mild in 5.9%. Following a year's treatment, there was an overall, not focal, improvement in activity, mild dominance rose to 58.2% and the others fell 2.4%. The other traces were unspecific. Clinical progression was good in 78.2% of cases, 19.5% of mild complications being resolved by lowering the drug dosage or by withdrawing it altogether. CONCLUSIONS: 1). ADHD is more likely to remain into adulthood and it has been associated to immunological disorders or epileptiform paroxysms, although only in a minority of cases. 2). The effect of MPH can be objectified by serial recordings of digitised cortical bioelectrical activity, with synchronised progression of the clinical response.

[Nocturnal polysomnographic study in children with attention deficit hyperactivity disorder]. / Estudio polisomnografico nocturno en niños con trastorno por deficit de atencion con hiperactividad.

INTRODUCTION: The main symptoms of attention deficit hyperactivity disorder (ADHD) are attention deficit, hyperactivity and impulsivity. Its prevalence lies between 3 and 5% in schoolchildren. Children with ADHD can present a high prevalence rate of comorbidity. A timely diagnosis and treatment can modify the educational and psychosocial development of most of these children. A number of subjective reports (especially from parents) describe sleep disorders. The objective verification of these disorders and the exact nature of the sleep problems are still to be determined and the purpose of this study is to deal with these issues. PATIENTS AND METHODS: We studied a sample of 48 children (9 females and 39 males) with a mean age of 8 (SD: 2.59) who met DSM IV criteria. They were submitted to a general exploration as well as a neurological exploration, including their patient record, and then they were evaluated using the DSM IV, which was carried out by parents and teachers (in order to evaluate two different environments), and a nocturnal polysomnographic study. In the sample there were 26 children with predominant attention deficit type ADHD (ADHD/AD); 4 children with predominant hyperactivity impulsivity type ADHD (ADHD/H); and 18 children with combined type ADHD (ADHD/C). RESULTS: The most frequently diagnosed subtype is the attention deficit subtype. The sleep architecture of children with ADHD presents the most consistent differences as compared to normal children in an increase in the percentage of phase 3 of sleep and, consequently, an increase in the percentage of slow sleep. Epileptiform type paroxysms were observed in 16.7% of the children who presented symptoms of ADHD. The number of epileptiform paroxysms is more usual in the attention deficit subtype. CONCLUSIONS: The increase in phase 3 may be related to the alterations in noradrenaline and dopamine transmission present in children who suffer from ADHD. Some children with ADHD can have a region of the brain with intense epileptic activity, which does not trigger epileptic seizures but gives rise to behavioural disorders, learning disorders and language problems.

[Face recognition in autism]. / Reconocimiento de caras en autismo.

INTRODUCTION: We conducted a survey of the literature on face recognition (FR), an activity that is essential for social relations and their dynamics. Unlike the recognition of non facial objects, this type of recognition is a special process since it is based on the detection of individual features. The most characteristic clinical parameter of autistic subjects is their inability to relate socially, possibly due to the difficulty they have in processing faces, although they are more skilled at recognising objects. DEVELOPMENT: We describe the two mechanisms involved in FR, one based on features and the other referring to the whole. The latter can be further divided into overall processing that allows a whole image to be compared with another previously assimilated image, and the processing of the arrangement of a face that is recognised as a whole. These may correspond to two different neuronal pathways. During the first days of life, the newborn baby has a predilection for faces in their feature and overall aspects, and processing of the arrangement is slower. Visual development in autistic children is erratic, similar to the level of a newborn infant, and their lack of interest for human faces is apparent during the first year of life, as they look at everything as if they were objects, that is, by features. CONCLUSIONS: The analysis of the literature enabled us to determine how FR mechanisms develop in the earliest days of the infant s life. It also highlighted the importance of the integrity of the pathway that facilitates stimulation for the recognition of facial arrangement, which is altered in autistic children perhaps from the peripheral area to the cortex. Further work on peripheral pathways and the fundamental cortical connections that are affected in autistic subjects will help us to understand the inefficiency of their facial arrangement recognition system.

[Cognitive evoked potentials in autistic children]. / Potenciales evocados cognitivos en niños autistas.

AIMS: The aim of this study was to examine the latency, amplitude and distribution of N400 potential in order to evaluate the semantic processing capacity in autistic children and in children suffering from Asperger s syndrome (AS), and to compare them with a control group. PATIENTS AND METHODS: 24 autistic children, six boys with AS and 25 controls, aged between 6 and 14 years old. The cases were examined using the DSM IV diagnostic criteria. Auditory stimulation was performed with pairs of congruent and incongruent words: two lists of 20 pairs of semantically related words (congruent) and 20 pairs of words with no semantic relationship whatsoever (incongruent). RESULTS: The most striking parameter is the increase in latency in N400 for the group of autistic children, which did not occur in the group of children with AS. Maximum N400 negativity for the children with autism was found in the left frontocentral region. No significant differences were observed for the amplitude of N400 between the three groups that were studied. CONCLUSION: Neurophysiologically, the autistic children and those affected by AS perhaps use different neuronal networks in semantic processing. The N400 wave can be a valid test for monitoring verbal processing in these children.

[Landau kleffner syndrome]. / Síndrome de Landau Kleffner.

INTRODUCTION: The Landau Kleffner syndrome (SLK) is associated with paroxystic alterations of the electroencephalogram which are intensified during sleep, with acquired aphasia and epilepsy, in 75 83% of the cases. The syndrome is associated with other features, such as personality disorders presenting as autistic behaviour, cognitive regression and in some cases, motor dysfunction. The epileptic activity appears to be responsible for the disorder. Treatment with anti epileptic drugs is ineffective in many cases, although there may be periods of spontaneous improvement, or there may be permanent sequelas of language. Design. A systematic revision of one case. CASE REPORT: A five year old boy with no previous clinical history had, at the age of four years, presented with behaviour changes and aphasia, accompanied by paroxystic changes on the EEG and nocturnal polysomnogram. On cranial CT there was a mid line cyst. He had had no seizures. Treatment. Treatment with carbamazepine led to clinical improvement in behaviour, reduction in the paroxysms and appearance of sleep spindles, but little effect on the degree of aphasia. CONCLUSIONS: The case described is a variant of SLK, with no epileptic seizures, some improvement on carbamazepine and a mid line cyst.

[Impact of meta-analysis in clinical practice: the example of psychiatry]. / Impacto del metaanálisis en la práctica clínica: el ejemplo de la psiquiatría.

BACKGROUND: To analyze the features of the studies on meta-analysis in psychiatry and assess the effect of these papers on the psychiatric reference textbooks. METHODS: Two researchers reviewed electronic databases Medline and Embase during the period 1977-98, using the key words: clinical trial, randomized observational trial, metaanalysis, systematic review. To confirm the validity of the searching strategy inter and intra-raters reliability was studied with satisfactory kappa figures. RESULTS: Psychiatry is the medical specialty in which more studies on meta-analysis have been carried out (N= 179, 11,79% out of the total), followed by cardiology and oncology. The increase in this kind of research during 1977-98 has been very high in all medical fields and, specifically, in psychiatry. There is no correlation between impact factor of a scientifical journal and number of meta-analysis published in it. Only 0.002% of the references of one of the most important textbook in psychiatry (Kaplan) are related to meta-analysis. There is no studies on meta-analysis developed by Spanish researchers. CONCLUSIONS: Studies on meta-analysis are not referred by psychiatric reference textbooks. As a consequence, their impact on clinical practice is scarce.

[Sleep in infantile autism]. / El sueño en el autismo infantil.

INTRODUCTION: Analysis of nocturnal sleep in infantile autism has been presented in various studies. However, there has been no systematization including the different structural and paroxystic alterations at the same time as permitting the development of a general theory of the effect of sleep on prognosis and treatment, particularly in a spectrum in which there is currently no definite solution. DEVELOPMENT: A systematic review was made of the literature obtained from publications included in MEDLINE and web pages of the last 25 years using the key words: autism, Asperger's disorder, sleep, childhood and Rett's syndrome. Altogether 21 papers fulfllled criteria for inclusion. Disorders of sleep in infantile autism were classified into three types: immaturity of sleep, showing a destructured polysomnographic recording and negative correlation with the level of development; functional alterations of sleep with early waking and difficulty in going to sleep being the disorders most frequently seen; and paroxystic alterations with epileptiform discharges being the commonest, without necessarily occurring together with seizures. The opinions stated on questionnaires and the data observed on the polysomnography were not in agreement. CONCLUSIONS: Analysis of the literature has permitted us to make an initial classification of sleep disorders in autistic children, and has shown a marked presence of these disorders in the evolution of autistic children. It is necessary that further studies being done, polysomnographic rather than by means of questionnaires, for two reasons: clinical and in order to obtain more precise classification.

[Pattern electroretinogram in anterior ischemic optic neuropathy]. / Pattern-electrorretinograma en neuropatía óptica isquémica anterior.

INTRODUCTION: Anterior ischemia optic neuropathy is defined as ischemia of the disc optic papilla nerve. The aetiology is multifactorial and causes ischemia of the optic disc and apoptosis of the nerve cells of the retina. OBJECTIVE: To study the retina of patients with anterior ischemia optic neuropathy by means of the electroretinogram pattern (PERG) to assess the function of ganglion cells of the inner layers of the retina. PATIENTS AND METHODS: We studied 12 patients referred from the Ophthalmology Department with the diagnosis of anterior ischemia optic neuropathy. The electrophysiological study consisted of PERG and PEV within 20 days of the episode. The latencies and amplitudes of the different components of the responses and the ratios of the PERG amplitudes were determined. RESULTS: No significant differences were seen in the P50 component of the PERG or the latency of the N95 component. However, statistically significant values were obtained for the amplitude N95. These differences were greater when measured from a nonlinear baseline. CONCLUSIONS: The PERG is useful for early diagnosis of patients with anterior ischaemia optic neuropathy. Measurement of the N95 is more useful when a nonlinear baseline is used. This shows dysfunction of the ganglion cells of the inner retina caused by ischaemia and retrograde degeneration of axons and cell bodies of the optic nerve.

[Post traumatic partial seizures]. / Crisis parciales postraumáticas.

INTRODUCTION: Post traumatic epilepsy represents 4% of the prevalence of the disorder and is one of the sequelas which is most difficult to prevent. Risk factors have been described to predict the appearance of seizures. CLINICAL CASE: A seven year old boy with a severe head injury was admitted to the Intensive Care Unit. On neuroimaging studies there were multiple foci of contusion, mainly in the left hemisphere, and blood in the III and IV ventricles and frontal horn of the left lateral ventricle. The patient had severe sequelae of head injury with a right spastic hemiplegia and hemiparesia with hypertony of the left side, together with complete blindness of both eyes due to bilateral atrophy of the optic nerve. Serial EEG were done, in which a recording showed alternating periods of hypervoltage grapho elements superimposed on a trace of very low voltage, with continuous activity of low voltage and low frequency. There were no grapho elements with acute morphology. However, the patient had a first partial seizure a year and a half after his head injury. On the EEG an epileptogenic focus was identified in the left hemisphere. Within two years of his head injury he had seven seizures. He had not received prophylactic antiepileptic treatment after the head injury. CONCLUSIONS: We report a case of epilepsy secondary to a head injury, in which the first seizure occurred one and a half years after injury. In view of the risk factors, we discuss whether prophylactic anti epileptic treatment might have been beneficial.

[Why evidence-based medicine? 20 years of meta-analysis]. / Por qué la medicina basada en la evidencia? 20 años de metaanálisis.

BACKGROUND: Meta-analysis, described within evidence-based medicine, has become a frequent issue in recent medical literature. An exhaustive search of reported meta-analysis from any medical specialty is described. MATERIAL AND METHODS: Search of papers included in Medline or Embase between 1973-1998. A study of intra and inter-reviewers liability about selection and classification have been performed. A descriptive analysis of the reported papers (frequency tables and graphics) is described, including differences of mean of reported meta-analysis papers by medical specialty and year. RESULTS: 1,518 papers were selected and classified. Most frequently found (45.91%) were: methodology (15.7%), psychiatry (11.79%), cardiology (10.01%) and oncology (8.36%). Inter personal agreement was 0.93 in selecting papers and 0.72 in classifying them. Between 1977-1987 overall mean of reported studies of meta-analysis (1.67 + 4.10) was significatively inferior to the 1988-1998 (49.54 + 56.55) (p < 0.001). Global number of meta-analysis was positively correlated (p < 0.05) with the number of studies about fundamentals and methodology during the study period. CONCLUSIONS: The method used to identify meta-analysis reports can be considered to be adequate; however, the agreement in classifying them in medical specialties was inferior. A progressive increase in the number of reported meta-analysis since 1977 can be demonstrated. Specialties with a greater number of meta-analysis published in the literature were: psychiatry, oncology and cardiology. Diffusion of knowledge about fundamentals and methodology of meta-analysis seems to have drawn and increase in performing and reporting this kind of analysis.

[Neurological sciences based on evidence]. / Ciencias neurológicas basadas en la evidencia.

OBJECTIVE: An exhaustive search of reported metanalysis from any medical speciality is described. MATERIAL AND METHODS: Search of papers included in MEDLINE or EMBASE between 1973-1998. A descriptive analysis of the reported papers (frequency tables and graphics) is described, including differences of mean of reported metanalysis papers by medical speciality and year. RESULTS: 1,514 papers were selected and classified. Between 1977-1987 overall mean of reported studies of neurologic metanalysis (1.20 +/- 1.10) was significatively inferior to the 1988-1998 (11.20 +/- 7.85) (p < 0.001). Global number of neurologic metanalysis was positively correlated (p < 0.05) with the number of studies about fundamentals and methodology during the study period. CONCLUSIONS: A progressive increase in the number of reported neurologic metanalysis since 1977 can be demonstrated. Diffusion of knowledge about fundamentals and methodology of metanalysis seems to have drawn and increase in performing and reporting this kind of analysis.

Medicina nuclear basada en la evidencia: 20 años de metaanálisis / Evidence based nuclear medicine: 20 years of metaanalysis

A mediados del siglo XIX Bichat y Magendi preconizaban un cambio sustancial en la manera de establecer las bases clínicas del diagnóstico precoz (1), el pronóstico y el tratamiento de las enfermedades que podemos considerar como la base de lo que hoy conocemos como medicina basada en la evidencia (MBE) que surgió formalmente hace 20 años en el seno de la gestión sanitaria (2) como método para facilitar la toma de decisiones y consecuentemente racionalizar la práctica clínica. El rápido avance de las técnicas diagnósticas y terapéuticas producido en los últimos años (3) dificulta alcanzar una experiencia personal válida y segura como "patrón" en la toma de decisiones clínicas. De ahí la necesidad de disponer de métodos que faciliten la puesta en práctica con cotidianidad de la MBE. Un método básico es el metaanálisis que, a través de métodos estadísticos, sintetizando los resultados de estudios independientes puede proporcionar estimaciones de los efectos de la atención sanitaria más precisas y conclusiones más contundentes que las derivadas de los estudios individuales incluidos en una revisión tradicional de la literatura médica. El metaanálisis tiene dos objetivos: combinar y resumir los resultados de estudios previos para ajustar los intervalos de confianza de los estimadores de efecto (entre otros el riesgo relativo, y la "odds ratio"), e identificar y explicar inconsistencias en los resultados de investigaciones previas