Tipos de estudios

Se incluyeron:

1. estudios diagnósticos de cohortes, prospectivos o retrospectivos, que reclutaron pacientes con traumatismo cerrado:

   1. sometidos a cualquier tipo de EPC como modalidad primaria de imagenología para detectar lesiones toracoabdominales; y

   2. sometidos también a pruebas de referencia de imagen o invasivas predefinidas para verificar los resultados de la EPC;

2. estudios que proporcionaron tablas 2 x 2 (o información suficiente para tabular los resultados) para permitir el cálculo de la sensibilidad, la especificidad y otros índices de exactitud de la prueba diagnóstica.

Se excluyeron:

1. los estudios diagnósticos de casos y controles que compararon pacientes con un estado conocido de casos con controles saludables, ya que este diseño crea poblaciones artificiales y tiende a sobrestimar la sensibilidad de la prueba índice;

2. las series de casos clínicos y los informes de casos;

3. los estudios con pruebas índice o de referencia poco claras; y

4. los estudios que no permitieron la creación de tablas 2 x 2.

Participantes

La población objetiva de esta revisión incluyó pacientes de cualquier edad o sexo que sufrieron cualquier tipo de traumatismo cerrado en un escenario civil y fueron trasladados a un hospital de cualquier nivel de atención. Además, para ser elegibles los participantes tenían que haber sido sometidos a una EPC como herramienta primaria de imagen y haber sido seguidos como enfermos hospitalizados o ambulatorios con diferentes modalidades diagnósticas para verificar si la afección de interés estaba presente o ausente.

Debido a las diferencias claras en el tratamiento clínico, se excluyeron de manera deliberada los pacientes con lesiones penetrantes, así como los miembros de las Fuerzas Armadas heridos en el campo de batalla.

Pruebas índice

Cualquier tipo de EPC realizada en un contexto de traumatismo (p.ej. ecografía FAST del abdomen o el tórax, o ambos, o cualquier protocolo de ecografía avanzada) concebida para detectar:

1. líquido libre (como substituto de hemorragia) en el abdomen, el espacio retroperitoneal o el tórax;

2. lesiones a órganos sólidos como el hígado o el bazo (incluidos los intentos para calificar la gravedad);

3. lesiones de vasos principales; y

4. otras lesiones (p.ej. neumotórax, como indica la presencia de aire en el espacio pleural).

Las variaciones en la tecnología y la aplicación de la EPC (p.ej. especificación de las máquinas y las sondas de ecografía y cuán actualizadas estaban, así como el tratamiento de los resultados no concluyentes de la prueba) se abordan en la sección de la revisión Evaluación de la calidad metodológica. Se planificó examinar su posible influencia en los cálculos de la exactitud diagnóstica en la sección de la revisión Investigaciones de la heterogeneidad.

Enfermedades de interés

Esta revisión se centró en el traumatismo cerrado toracoabdominal y múltiple, que significa cualquier fuerza contusa y no penetrante al abdomen y el tórax y a las vísceras sólidas y huecas, así como a los vasos principales. Las afecciones objetivo consideradas en esta revisión incluyeron:

1. líquido libre en:

   1. la cavidad torácica (uni o bilateral, cuando se especificó);

   2. la cavidad abdominal (por cuadrante abdominal, cuando se especificó);

   3. el espacio retroperitoneal;

   4. el pericardio; o

   5. el mediastino;

2. lesiones de órganos, definidas como:

   1. lesiones hepáticas (p.ej. desgarros capsulares, hematoma, desgarros de tejidos);

   2. lesiones esplénicas (p.ej. desgarros capsulares, hematoma, desgarros de tejidos);

   3. lesiones a otros órganos sólidos (p.ej. páncreas, riñones);

   4. lesiones a vísceras huecas; o

   5. desgarros de cualquier otro órgano por ecografía;

3. lesiones vasculares, definidas como:

   1. disección o rotura de la aorta torácica o abdominal, o ambas;

   2. rotura de otros vasos como las arterias ilíacas;

4. otras lesiones (p.ej. neumotórax, indicado por la presencia de aire en el espacio pleural en la cavidad torácica).

Como parte de las Investigaciones de la heterogeneidad se analizó el efecto de los diferentes tipos de afecciones objetivo. Las afecciones objetivo se categorizan como substitutos de traumatismo cerrado (es decir, líquido libre y aire libre, llamada evaluación limitada), y signos substitutos y directos de daño a órganos (es decir, lesiones de órganos y lesiones vasculares, llamada evaluación completa).

Estándares de referencia

Para aceptarlo como un estándar de referencia diagnóstico, se debía especificar el uso deliberado (y el razonamiento para su uso) del método específico. Para evitar el sesgo de verificación, todos los participantes debían recibir un estudio por imagen o una prueba invasiva independientes, aparte del examen inicial con EPC.

Las siguientes pruebas se clasificaron como estándares de referencia para confirmar la presencia o ausencia de la afección objetivo:

1. cualquier tipo de tomografía computarizada de las cavidades corporales principales (es decir, tórax, abdomen, pelvis), selectiva o realizada como examen de todo el cuerpo. Se planificó estratificar los resultados para el uso de agentes de contraste intravenosos u orales, o ambos, y el intervalo entre la EPC y la TC;

2. cualquier tipo de IRM de las cavidades corporales principales;

3. laparotomía (mediante abordaje mediano o transversal) o laparoscopia, diagnóstica o terapéutica;

4. toracotomía (mediante abordaje por esternotomía mediana o clamshell) o toracoscopia, diagnóstica o terapéutica;

5. autopsia, hecha por patólogos o por forenses.

Búsquedas electrónicas

We searched the following electronic sources.

1. Ovid MEDLINE (1946 to 15 July 2017).

2. PubMed (not MEDLINE) (1947 to 15 July 2017).

3. Ovid Embase (1974 to 15 July 2017).

Search strategies are shown in Appendix 1.

We performed a further search on 6 December 2018; details of the eight potentially relevant studies identified have been added to the Characteristics of studies awaiting classification and Studies awaiting classification sections, and may be incorporated into the review at the next update.

Búsqueda de otros recursos

A systematic review by Scherer and colleagues showed that results from studies that have not been published in a full‐text format are systematically different from fully published results (Scherer 2007). We therefore searched the BIOSIS database for conference abstracts to identify potentially relevant studies that had not yet been published in a journal format (see Appendix 1).

We planned to contact authors of individual studies by email, letter, or phone, if we considered their results to be important but needed further explanation or raw data. We guaranteed that any data exchange complied with the International Conference on Harmonisation Good Clinical Practice (ICH‐GCP) principles and rules and regulations of data safety and security.

Selección de los estudios

Two review authors (AH, JL) independently screened the titles and abstracts of the identified reports, documenting details of selected studies in a predefined electronic spreadsheet and assessing studies for eligibility in terms of the predefined inclusion and exclusion criteria. If it was not possible to make a decision based on title and abstract alone, the full texts of potentially relevant studies were assessed. Any disagreements between authors regarding the selection of studies were resolved by a third expert (DS). The study selection process is documented in a detailed flow chart (Figure 1).

Extracción y manejo de los datos

As stated above, we established an SOP for data extraction for systematic reviews, meta‐analyses, and health technology assessment (HTA) reports. We adhered to ICH‐GCP, Good Epidemiological Practice (GEP), and other relevant rules and recommendations. We have trained personnel on site to record, manage, and audit data, and our data storage modes comply with federal legislation on data safety for research purposes. Two review authors (AH, JL) independently extracted data from original papers in duplicate, and resolved discrepancies by discussion, moderated by a third review author (DS). They extracted the following information from published papers:

1. study characteristics (author, year of study, year of publication, journal reference, study design, inclusion/exclusion criteria, operator characteristics, hardware specifications, index test used, reference test used, general setting (urban/rural), mass casualty (yes/no));

2. patient characteristics (age, gender, type of trauma, type of injury, injury severity, haemodynamic stability, probability of survival);

3. outcome of the index test as assessed in the individual studies by diagnosing the target condition and, if available, the number of participants with inconclusive results or who had no test result;

4. diagnostic 2 x 2 tables, cross‐classifying the disease status on the basis of the reference test (i.e. number of true‐positive, false‐positive, false‐negative, and true‐negative results).

Diagnostic accuracy was expressed by individual and pooled indicators such as sensitivity and specificity with 95% confidence intervals (CI), positive and negative likelihood ratios (LR), positive predictive value (PPV), negative predictive value (NPV), and the summary receiver operating characteristic curve (SROC).

Evaluación de la calidad metodológica

Two review authors (AH, JL) independently used the QUADAS‐2 tool (the revised and updated version of the original Quality Assessment of Diagnostic Accuracy Studies list of items) to assess methodological quality of individual studies (Whiting 2011). Any discrepancies were resolved by discussion, moderated by a third review author (DS). QUADAS‐2 includes four main domains, namely: patient selection, index test, reference standard, and flow and timing. We assessed each domain with regard to risk of bias, rating them as 'low', 'high', or 'unclear'. We assessed concerns regarding applicability only for the first three domains, categorising them as 'low', 'high', or 'unclear'. Signalling questions were answered as 'yes', 'no', or 'unclear' (see also Appendix 2). By using tailored review‐specific signalling questions we were able to perform a custom‐made assessment of the methodological quality of all included studies. We omitted the signalling question "Was any case‐control design avoided?" in Domain 1: Patient selection since we did not include any case control study, case series, or case reports. We added three signalling questions to Domain 2: Index test and two signalling questions to Domain 3: Reference test referring to operator's expertise and background, technical features of the hardware, and appropriateness of the ultrasound protocol and reference imaging standard. In Domain 4: Flow and timing, we included the signalling question "Did all participants receive a reference standard?" in order to explore the risk of partial verification bias.

Análisis estadístico y síntesis de los datos

If at least one of the target conditions was detected (i.e. pneumothorax, free fluid, organ or vessel injury), we considered the patient (participant) to be traumatised or test‐positive. Otherwise, we considered the participant to be uninjured or test‐negative. Our observational unit of interest was thus the individual participant, not a particular injury, and we did not evaluate single target conditions separately in the primary analysis. We used inconclusive test results as reported in the primary studies. For individual studies, we calculated sensitivity and specificity with 95% CI, tabulated pairs of sensitivity and specificity with CI, and depicted estimates by coupled forest plots using Review Manager 5 (RevMan 5) (Review Manager 2014).

Due to the subjective nature of the interpretation of POCS findings, we expected implicit thresholds in test positivity. We assessed a possible threshold effect visually by plotting true‐positive rates (sensitivity) from each study against false‐positive rates (1 − specificity) in a receiver operating characteristic (ROC) space and coupled forest plots of sensitivity and specificity. Since the dichotomous operationalisation of the test result does not enable explicit thresholds, we used the bivariate model according to Reitsma 2005, which is a robust statistical model taking the underlying relationship between sensitivity and specificity into account. The random‐effects approach allows for calculating sensitivity and specificity estimates while controlling for heterogeneity across studies. We fitted the models in Stata (Stata 2017) using the 'metandi' command and produced SROC plots using RevMan 5. We estimated average sensitivities and specificities using the bivariate model. We obtained likelihood ratios post estimation using the parameters of the bivariate model (see Summary of findings table 1).

Investigación de la heterogeneidad

We assessed heterogeneity visually by inspecting the coupled forest plots and plots of study results in the SROC space. We also investigated possible sources of heterogeneity by adding single covariates to the basic bivariate random‐effects model. We conducted fitting of the bivariate model via the 'xtmelogit' command in Stata (Takwoingi 2016). We investigated the effect of adding covariates by conducting a likelihood ratio test that compared the ‐2 log likelihoods of the basic bivariate model to a model including a single covariate. If a significant reduction in the ‐2 log likelihood was detected (indicated by a P value of < 0.05), test performance was considered to be associated with the particular covariate. For statistically significant test results, we determined whether the covariate was associated with the estimated sensitivity, specificity, or both (Macaskill 2011), by removing the covariate terms for either sensitivity or specificity, and comparing the fit of each alternative model using likelihood ratio tests.

For tests of heterogeneity, we required a minimum of 10 studies in total and at least four studies per subgroup. We had to dichotomise the covariates we investigated, and differentiate between paediatric and non‐paediatric (i.e. adult/mixed populations), surrogates of injury (e.g. air, free fluid) and organ lacerations, abdominal injuries (i.e. injuries exclusively located in the abdomen) or chest injuries (i.e. injuries exclusively located in the chest), and single CT versus CT plus laparotomy used as reference standard (see Summary of findings table 2).

Análisis de sensibilidad

We performed sensitivity analyses to investigate how individual QUADAS‐2 key domains (i.e. patient selection, index test, reference standard, and flow and timing) affected accuracy estimates, and to explore whether the different evaluations of the two independent review authors within two original studies influenced pooled sensitivities or specificities, or both, of the index test. Moreover, we examined the impact of participants' age on accuracy estimates by only including paediatric studies.

Evaluación del sesgo de notificación

We did not assess reporting bias because there are no accepted ways of doing this for diagnostic test accuracy studies (Deeks 2005).