When the p Value Doesn't Cut It: The Fragility Index Applied to Randomized Controlled Trials in Colorectal Surgery.

BACKGROUND: The American Statistical Association, among others, has called for the use of statistical methods beyond p ≤ 0.05. The fragility index is a statistical metric defined as the minimum number of patients for whom if an event rather than a nonevent occurred, then the p value would increase to ≥0.05. Previous reviews have demonstrated that many randomized controlled trials have a low fragility index, suggesting they may not be robust. OBJECTIVE: The purpose of this study was to review the fragility indices of randomized controlled trials in colorectal surgery. DATA SOURCES: A PubMed search was performed. STUDY SELECTION: Colorectal surgery randomized controlled trials with a dichotomous primary outcome p ≤ 0.05 and publication between 2016 and 2018 were systematically identified. INTERVENTIONS: All procedural interventions related to colorectal surgery were included. MAIN OUTCOME MEASURES: The main measures were the fragility index and the number of patients lost to follow-up for each trial. The percentage of trials with the number of patients lost to follow-up greater than the fragility index was calculated. RESULTS: In total, 712 abstracts were reviewed, with 90 trials meeting the inclusion criteria. The median fragility index was 3 (interquartile range of 1 to 10). In 51 of the 90 trials (57%), the number of patients lost to follow-up was greater than the fragility index. LIMITATIONS: The fragility index is only one measure of the robustness of a randomized clinical trial. CONCLUSIONS: Most colorectal surgery randomized controlled trials have a low fragility index. In 57% of trials, more patients were lost to follow-up than would be required to change the outcome of the trial from "significant" to "nonsignificant" based on the p value. This emphasizes the importance of assessing the robustness of clinical trials when considering their clinical application, rather than relying solely on the p value. See Video Abstract at http://links.lww.com/DCR/B741.CUANDO EL VALOR-P ES INSUFICIENTE: ÍNDICE DE FRAGILIDAD APLICADO EN ESTUDIOS ALEATORIOS CONTROLADOS EN CIRUGÍA COLORECTAL. ANTECEDENTES: La Sociedad Estadounidense de Estadística, entre otros, ha pedido el uso de métodos estadísticos más allá de p <0,05. El índice de fragilidad es una medida estadística definida como el número de desenlaces que podrían cambiar para revertir, o conseguir, la significación estadística, así el valor p aumentaría a ≥ 0,05. Las revisiones anteriores han demostrado que muchos estudios aleatorios controlados tienen un índice de fragilidad bajo, lo que sugiere que pueden poco sólidos. OBJETIVO: El propósito de la présente investigación fué de revisar los índices de fragilidad de los estudios aleatorios controlados en cirugía colorrectal. FUENTES DE DATOS: PubMed. SELECCIN DE ESTUDIOS: Se identificaron sistemáticamente estudios aleatorios controlados de cirugía colorrectal con un resultado primario dicotómico, valor de p ≤ 0,05 y publicados entre 2016-2018. INTERVENCIONES: Se incluyeron todas aquellas intervenciones con procedimientos relacionados con la cirugía colorrectal. PRINCIPALES MEDIDAS DE RESULTADO: Las principales medidas fueron: el índice de fragilidad y el número de pacientes perdidos durante el seguimiento en cada estudio. Se calculó el el índice de fragilidad en porcentaje de estudios con el mayor número de pacientes perdidos durante el seguimiento mas prolongado. RESULTADOS: En total, se revisaron 712 resúmenes con 90 ensayos que cumplieron con los criterios de inclusión. La mediana del índice de fragilidad fue de 3 (rango intercuartíl de 1 a 10). En 51 de los 90 estudios (57%), el número de pacientes perdidos durante el seguimiento fue mayor que el índice de fragilidad. LIMITACIONES: El índice de fragilidad es solo una medida de la robustez de un estúdio clínico aleatorio. CONCLUSIONES: La mayoría de los estudios aleatorios y controlados en cirugía colorrectal tienen un índice de fragilidad bajo. En el 57% de los estudios, se perdieron más pacientes durante el seguimiento de los que se necesitarían para cambiar el resultado del estudios de grado "significativo" a un grado "no significativo" según el valor-p. Este concepto enfatiza la importancia de evaluar la robustez de los estudios clínicos al considerar su aplicación verdadera aplicación clínica, en lugar de depender únicamente del valor-p. Consulte Video Resumen en http://links.lww.com/DCR/B741. (Traducción-Dr. Xavier Delgadillo).

Imaging Modalities for Evaluation of Intestinal Obstruction.

It is essential for the colon and rectal surgeon to understand the evaluation and management of patients with both small and large bowel obstructions. Computed tomography is usually the most appropriate and accurate diagnostic imaging modality for most suspected bowel obstructions. Additional commonly used imaging modalities include plain radiographs and contrast imaging/fluoroscopy, while less commonly utilized imaging modalities include ultrasonography and magnetic resonance imaging. Regardless of the imaging modality used, interpretation of imaging should involve a systematic, methodological approach to ensure diagnostic accuracy.

The incidence of urolithiasis among commercial aviation pilots.

PURPOSE: A kidney stone event in a commercial aviation pilot has significant vocational implications since the Federal Aviation Administration specifically prohibits medical certification in the setting of recent or recurrent stone disease. Given these serious concerns, an understanding of the burden of stone disease on the commercial aviation community is important. Thus, we performed a study in partnership with the Federal Aviation Administration to better characterize the epidemiology of this condition. MATERIALS AND METHODS: We reviewed the Federal Aviation Administration Aerospace Medical Certification database for 2000 through 2007. Pilots with a class I certificate (scheduled commercial aviation) were selected for further review. All medical certificates submitted with a pathology code of 573 (urolithiasis) were identified for analysis. RESULTS: From 2000 through 2007 between 3.7% and 4.6% of scheduled commercial aviation pilots were diagnosed with urolithiasis. However, during the study period there was a significant decrease in the proportion of pilots diagnosed with urolithiasis. CONCLUSIONS: A meaningful number of commercial aviation pilots are affected by urolithiasis each year. Our analysis detected a significant decrease in the proportion of affected pilots, although the reason for this trend is not well understood. It may be that changes in the occupational environment that could affect risk factors for stone formation are responsible. Further efforts to characterize stone risk in this unique population are welcome, given the larger vocational and societal consequences of a stone event in the setting of airline transport.

Assessment of three dead detector correction methods for cone-beam computed tomography.

PURPOSE: Dead detectors due to manufacturing defects or radiation damage in the electronic portal imaging devices (EPIDs) used for cone-beam computed tomography (CBCT) can lead to image degradation and ring artifacts. In this work three dead detector correction methods were assessed using megavoltage CBCT (MVCBCT) as a test system, with the goals of assessing the relative effectiveness of the three methods and establishing the conditions for which they fail. METHODS: MVCBCT projections acquired with four linacs at 8 and 60 MU (monitor units) were degraded with varying percentages (2%-95%) of randomly distributed dead single detectors (RDSs), randomly distributed dead detector clusters (RDCs) of 2 mm diameter, and nonrandomly distributed dead detector disks (NRDDs) of varying diameter (4-16 mm). Correction algorithms were bidirectional linear interpolation (BLI), quad-directional linear interpolation (QLI), and a Laplacian solution (LS) method. Correction method failure was defined to occur if ring artifacts were present in the reconstructed phantom images from any linac or if the modulation transfer function (MTF) for any linac dropped below baseline with a p value, calculated with the two sample t test, of less than 0.01. RESULTS: All correction methods failed at the same or lower RDC/RDS percentages and NRDD diameters for the 60 MU as for the 8 MU cases. The LS method tended to outperform or match the BLI and QLI methods. If ring artifacts anywhere in the images were considered unacceptable, the LS method failed for 60 MU at >33% RDS, >2% RDC, and >4 mm NRDD. If ring artifacts within 4 mm longitudinally of the phantom section interfaces were considered acceptable, the LS method failed for 60 MU at >90% RDS, >80% RDC, and >4 mm NRDD. LS failed due to MTF drop for 60 MU at >50% RDS, >25% RDC, and >4 mm NRDD. CONCLUSIONS: The LS method is superior to the BLI and QLI methods, and correction algorithm effectiveness decreases as imaging dose increases. All correction methods failed first due to ring artifacts and second due to MTF drop. If ring artifacts in axial slices within a 4 mm longitudinal distance from phantom section interfaces are acceptable, statistically significant loss in spatial resolution does not occur until over 25% of the EPID is covered in randomly distributed dead detectors, or NRDDs of 4 mm diameter are present.

Masimo Perfusion Index Versus Doppler for Tourniquet Effectiveness Monitoring.

BACKGROUND: In addition to a plethysmograph, Masimo pulse oximeters display a Perfusion Index (PI) value. This study investigated the possible usefulness of PI for monitoring limb tourniquet arterial occlusion. METHODS: Tactical Ratcheting Medical Tourniquets were applied to the thighs of 15 subjects. Tightening ended at one ratchet-tooth advance beyond Doppler- indicated occlusion. The times and pressures of Doppler and PI signal absences and returns were recorded. RESULTS: Intermittent PI signal error occurred in 149 of 450 runs (PI, 33% versus Doppler, 0%; p < .0001). PI signal loss lagged Doppler-indicated occlusion by 19 ± 15 seconds (mean ± standard deviation, p < .0001). PI Signal Return lagged tourniquet release by 13 ± 7 seconds (Doppler Signal Return took 1 ± 1 seconds following tourniquet release; p < .0001). PI failed to detect early Doppler audible pulse return in 30 of 39 occurrences. CONCLUSION: The PI available on Masimo pulse oximeters is not appropriate for monitoring limb tourniquet effectiveness.

The Acute Upper Gastrointestinal Bleed.

Upper gastrointestinal bleeding (UGIB), defined as intraluminal hemorrhage proximal to the ligament of Treitz, can range from mild and asymptomatic to massive life-threatening hemorrhage. For the purposes of this article, the authors define an acute UGIB to be one that results in new acute symptoms and is, therefore, potentially life-threatening. UGIB requires a systematic approach to evaluation and treatment, similar to the management of a trauma patient. Surgeon involvement in UGIBs remains integral despite the rare need for operative management. Endoscopy is the primary tool for diagnosis and treatment.

Effects of Distance Between Paired Tourniquets.

BACKGROUND: In practice, the distance between paired tourniquets varies with unknown effects. METHODS: Ratcheting Medical Tourniquets were applied to both thighs of 15 subjects distally (fixed location) and proximally (0, 2, 4, 8, 12cm gap widths, randomized block). Applications were pair, single distal, single appropriate proximal. Tightening ended one-ratchet tooth advance past Doppler-indicated occlusion. Pairs had alternating tightening starting distal. RESULTS: Occlusion pressures were higher for: each single than respective individual pair tourniquet, each pair distal than respective pair proximal, and each single distal than respective single proximal (all p < .0001). Despite thigh circumference increasing proximally, occlusion pressures were lower with proximal tourniquet involvement (pair or single, p < .0001). Occlusion losses before 120 seconds occurred most frequently with pairs (0cm 4, 2cm 4, 4cm 6, 8cm 7, 12cm 5 for 26 of 150), in increasing frequency with increasingly proximal singles (0cm 0, 2cm 1, 4cm 1, 8cm 2, 12cm 6 for 10 of 150, p < .0001 for trend), and least with single distal (2 of 150, p < .0001). Paired tourniquets required fewer ratchet advances per tourniquet (pair distal 5 ± 1, pair proximal 4 ± 1, single distal 6 ± 1, single proximal 6 ± 1). Final ratchet tooth advancement pressure increases (mmHg) were greatest for singles (distal 61 ± 10, proximal 0cm 53 ± 7, 2cm 51 ± 9, 4cm 50 ± 7, 8cm 45 ± 7, 12cm 36 ± 7) and least in pairs (distal 41 ± 8, proximal 32 ± 7) with progressively less pair interaction as distance increased (pressure change for the pair tourniquet not directly advanced: 0cm 13 ± 4, 2cm 10 ± 4, 4cm 6 ± 3, 8cm 1 ± 2, 12cm -1 ± 2). CONCLUSIONS: Occlusion pressures are lower for paired than single tourniquets despite variable intertourniquet distances. Very proximal placement has a pressure advantage; however, pairs and very proximal locations may be less likely to maintain occlusion. Increasingly proximal placements also increase tissue at risk; therefore, distal placements and minimal intertourniquet distances should still be recommended.

Comparative mitogenomic analyses of three North American stygobiont amphipods of the genus Stygobromus (Crustacea: Amphipoda).

The mitochondrial genomes of three North American stygobiont amphipods Stygobromus tenuis potomacus, S. foliatus and S. indentatus collected from Caroline County, VA, were sequenced using a shotgun sequencing approach on an Illumina NextSeq500 (Illumina Inc., San Diego, CA). All three mitogenomes displayed 13 protein-coding genes, 22 tRNAs and two rRNAs typical of metazoans. While S. tenuis and S. indentatus displayed identical gene orders similar to the pancrustacean ground pattern, S. foliatus displayed a transposition of the trnL2-cox2 genes to after atp8-atp6. In addition, a short atp8 gene, longer rrnL gene and large inverted repeat within the Control Region distinguished S. foliatus from S. tenuis potomacus and S. indentatus. Overall, it appears that gene order varies considerably among amphipods, and the addition of these Stygobromus mitogenomes to the existing sequenced amphipod mitogenomes will prove useful for characterizing evolutionary relationships among various amphipod taxa, as well as investigations of the evolutionary dynamics of the mitogenome in general.