The clinical use of statistical permutation test methodology: a tool for identifying predictive variables of outcome

Association Between Preoperative Hydronephrosis and Prognosis After Radical Cystectomy Among Patients With Bladder Cancer: A Systemic Review and Meta-Analysis

Background: Preoperative hydronephrosis (HN) might be associated with adverse outcomes in patients who underwent radical cystectomy (RC). The aim of this study was to evaluate the effect of preoperative HN on the oncological outcomes in patients with bladder cancer who underwent RC by performing a systemic review and meta-analysis.

Methods: A systematic literature review in PubMed, EMBASE, and Scopus was conducted by searching the terms “bladder cancer,” “cystectomy,” and “hydronephrosis” until December 2016, in accordance with the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines. The calculated end points were advanced disease stage, cancer-specific survival (CSS), and overall survival (OS).

Results: Twenty-four studies involving 10,461 patients who underwent RC were included. Among the patients, 3,121 (29.8%) had preoperative HN. The pooled analysis showed that preoperative HN had a significant association with advanced stage (odds ratio, 2.56, 95% confidence interval [CI], 1.91–3.42, p < 0.00001), lymph node invasion (OR, 2.44, 95% CI, 1.79–3.34, p < 0.00001), CSS (hazard ratio [HR], 1.67, 95% CI, 1.34–2.08, p < 0.00001), and OS (HR, 1.51, 95% CI, 1.30–1.75, p < 0.00001).

Conclusions: Among patients with bladder cancer who underwent RC, preoperative HN could be a significant predictor of bladder cancer survival. However, large well-designed prospective studies are required to confirm the precise prognostic significance of preoperative HN.

Differential metabolomics analysis allows characterization of diversity of metabolite networks between males and females

Females and males are known to have different abilities to cope with stress and disease. This study was designed to investigate the effect of sex on properties of a complex interlinked network constructed of central biochemical metabolites. The study involved the blood collection and analysis of a large set of blood metabolic markers from a total of 236 healthy participants, which included 140 females and 96 males. Metabolic profiling yielded concentrations of 168 metabolites for each subject. A differential correlation network analysis approach was developed for this study that allowed detection and characterization of interconnection differences in metabolites in males and females. Through topological analysis of the differential network that depicted metabolite differences in the sexes, we identified metabolites with high centralities in this network. These key metabolites were identified as 10 phosphatidylcholines (PCaaC34:4, PCaaC36:6, PCaaC34:3, PCaaC42:2, PCaeC38:1, PCaeC38:2, PCaaC40:1, PCaeC34:1, PC aa C32:1 and PC aa C40:6) and 4 acylcarnitines (C3-OH, C7-DC, C3 and C0). Identification of these metabolites may help further studies of sex-specific differences in the metabolome that may underlie different responses to stress and disease in males and females.

Bonferroni-Holm and permutation tests to compare health data: methodological and applicative issues

BACKGROUND

Statistical methodology is a powerful tool in the health research; however, there is wide accord that statistical methodologies are not usually used properly. In particular when multiple comparisons are needed, it is necessary to check the rate of false positive results and the potential inflation of type I errors. In this case, permutation testing methods are useful to check the simultaneous significance level and identify the most significant factors.

METHODS

In this paper an application of permutation tests, in the medical context of Inflammatory Bowel Diseases, is performed. The main goal is to assess the existence of significant differences between Crohn's Disease (CD) and Ulcerative Colitis (UC). The Sequentially Rejective Multiple Test (Bonferroni-Holm procedure) is used to find which of the partial tests are effectively significant and solve the problem of the multiplicity control.

RESULTS

Applying Non-Parametric Combination (NPC) Test for partial and combined tests we conclude that Crohn's Disease patients and Ulcerative Colitis patients differ between them for most examined variables. UC patients compared with the CD patients, have a higher diagnosis age, not show smoking status, proportion of patients treated with immunosuppressants or with biological drugs is lower than the CD patients, even if the duration of such therapies is longer. CD patients have a higher rate of re-hospitalization. Diabetes is more present in the sub-population of UC patients. Analyzing the Charlson score we can highlight that UC patients have a more severe clinical situation than CD patients. Finally, CD patients are more frequently subject to surgery compared to UC. Appling of the Bonferroni Holm procedure, which provided adjusted p-values, we note that only nine of the examined variables are statistically significant: Smoking habit, Immunosuppressive therapy, Surgery, Biological Drug, Diabetes, Adverse Events, Re-hospitalization, Gender and Duration of Immunosoppressive Therapy. Therefore, we can conclude that these are the specific variables that can discriminate effectively the Crohn's Disease and Ulcerative Colitis groups.

CONCLUSIONS

We identified significant variables that discriminate the two groups, satisfying the multiplicity problem, in fact we can affirm that Smoking habit, Immunosuppressive therapy, Surgery, Biological Drug, Diabetes, Adverse Events, Hospitalization, Gender and Duration of Immunosoppressive Therapy are the effectively significant variables.

Performances of low level hospital health caregivers after a neonatal resuscitation course

Background

High fidelity simulation has been executed to allow the evaluation of technical and non-technical skills of health caregivers. Our objective was to assess technical and non-technical performances of low level hospitals health caregivers who attended a Neonatal Resuscitation course using high fidelity simulation in a standard-setting scenario.

Methods

Twenty-three volunteers were asked to manage a simple scenario (infant with secondary apnea) after the course. Technical and non-technical skills were assessed by using previously published scores. Performances were assessed during the scenario and after 2 months by filmed video recordings.

Results

Sixteen (69.5%) participants failed to pass the minimum required technical score. Staff experience and participation in previous courses were associated to higher score in technical and non-technical skills, while working in level I or II hospitals did not affect the scores. Previous experience in neonatal resuscitation requiring positive pressure ventilation was associated to better non-technical performance. Technical and non-technical scores were significantly correlated (r = 0.67, p = 0.0005). Delayed and direct evaluation of technical skills provided the same scores.

Conclusions

A neonatal resuscitation course, performed by using a high fidelity simulation manikin, had a limited impact on technical and non-technical skills of participants working in low level hospitals. Training programs should be tailored to the participants’ professional background and to the more relevant sessions.