Hypothesis Probability or Statistical Significance?

Methodology ◽  
2009 ◽  
Vol 5 (1) ◽  
pp. 35-39
Author(s):  
Emilia I. De la Fuente ◽  
Gustavo R. Cañadas ◽  
Joan Guàrdia ◽  
Luis M. Lozano
Keyword(s):  
Normal Distribution ◽  
Statistical Inference ◽  
21St Century ◽  
Statistical Significance ◽  
Research Data ◽  
The Mean

After almost a century of debate among renowned statisticians, 21st century traditional Statistical Inference is marked by controversy over the application of the procedures for hypothesis estimation and contrast. The aim of this paper is twofold: First, to present various debatable issues that arise when the mean in a Normal distribution of known precision is contrasted and second, to argue the suitability of Bayesian philosophy for the analysis of research data.

Interval estimation of the mean of a normal distribution based on quantized observations

2009 ◽  
Vol 59 (5) ◽  
Author(s):  
Viktor Witkovský ◽  
Gejza Wimmer
Keyword(s):  
Standard Deviation ◽  
Measurement Error ◽  
Normal Distribution ◽  
Statistical Inference ◽  
Interval Estimation ◽  
Small Sample ◽  
Measurement Device ◽  
Analog To Digital ◽  
The Mean ◽  
Interval Estimators

AbstractWe consider the problem of making statistical inference about the mean of a normal distribution based on a random sample of quantized (digitized) observations. This problem arises, for example, in a measurement process with errors drawn from a normal distribution and with a measurement device or process with a known resolution, such as the resolution of an analog-to-digital converter or another digital instrument. In this paper we investigate the effect of quantization on subsequent statistical inference about the true mean. If the standard deviation of the measurement error is large with respect to the resolution of the indicating measurement device, the effect of quantization (digitization) diminishes and standard statistical inference is still valid. Hence, in this paper we consider situations where the standard deviation of the measurement error is relatively small. By Monte Carlo simulations we compare small sample properties of the interval estimators of the mean based on standard approach (i.e. by ignoring the fact that the measurements have been quantized) with some recently suggested methods, including the interval estimators based on maximum likelihood approach and the fiducial approach. The paper extends the original study by Hannig et al. (2007).

scholarly journals SAT0221 FACTORS AFFECTING MORTALITY OF SYSTEMIC LUPUS ERYTHEMATOSUS PATIENTS IN SPAIN IN THE 21ST CENTURY: DATA FROM THE RELESSER REGISTRY

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1053.2-1054
Author(s):  
C. Moriano ◽  
J. Calvo ◽  
I. Rua-Figueroa ◽  
E. Diez Alvarez ◽  
C. Bermúdez ◽  
...  
Keyword(s):  
Systemic Lupus Erythematosus ◽  
Disease Activity ◽  
21St Century ◽  
Lupus Erythematosus ◽  
Statistical Significance ◽  
Systemic Lupus ◽  
Research Support ◽  
Vascular Events ◽  
Delay In Diagnosis ◽  
The Mean

Background:The mortality in Systemic Lupus Erythematosus (SLE) varies largely across different countries most probably due to social, healthcare and ethnic differences.Objectives:To analyze the causes and identify predictive factors of mortality of SLE in Spain in the present century.Methods:We performed a cross-sectional and retrospective study analyzing data from the RELESSER cohort (Spanish Registry of Systemic Lupus Erythematosus of the Spanish Society of Rheumatology). We included all patients diagnosed with SLE since the year 2000 and recorded sociodemographic, clinical and serological variables, comorbidities and treatments, as well as indicators of disease activity, damage and severity. The characteristics of the deceased patients were compared with those of the survivors, and variables with clinical significance or statistical significance were grouped into multivariate models to determine which ones were independently associated with the outcome of the disease.Results:A total of 2004 patients were included, 88.6% female, the mean age at diagnosis was 38.3 (± 15.3) years, with a mean delay in diagnosis of 28.9 (± 52.6) months. Up to 2.84% of the individuals had died. The leading cause of death was SLE activity (n=16), followed by infections (n=14), vascular events (n=7) and cancer (n=6). The mean age of death was 54.68 (± 20.13) years, and neither age, sex nor delay in diagnosis was independently associated with mortality. The presence of nephritis, depression, severe infections, organ damage (SLICC/ACR DI) or disease activity (SLEDAI), as well as the use of cyclophosphamide, rituximab or high doses of corticosteroids, were predictors of mortality in our cohort. Antimalarial treatment and skin manifestations were linked to improved survival.Conclusion:In the RELESSER cohort, clinical factors, co-morbidities, as well as therapeutic attitudes were associated with a significant increase in mortality in SLE. Interestingly, depression was independently associated to mortality. The activity of the disease and infections continue to be the main causes of death at the beginning of the 21st century amongst our patients.Disclosure of Interests:Clara Moriano: None declared, Jaime Calvo Grant/research support from: Lilly, UCB, Consultant of: Abbvie, Jansen, Celgene, Iñigo Rua-Figueroa: None declared, Elvira Diez Alvarez: None declared, Cristina Bermúdez: None declared, Francisco J López-Longo Grant/research support from: AbbVie and GSK, Speakers bureau: AbbVie, Actelion, Bristol Myers Squibb, GSK, MSD, Pfizer, Roche, and UCB Pharma, María Galindo-Izquierdo: None declared, Alejandro Olive: None declared, Eva Tomero Muriel: None declared, Antonio Fernandez-Nebro: None declared, Mercedes Freire González: None declared, Olaia Fernández- Berrizbeitia: None declared, Ana Pérez Gómez: None declared, Esther Uriarte Isacelaya: None declared, Carlos Marras Fernandez Cid: None declared, Carlos A. Montilla-Morales: None declared, Gregorio Santos Soler: None declared, Ricardo Blanco Grant/research support from: AbbVie, MSD, and Roche, Speakers bureau: AbbVie, Pfizer, Roche, Bristol-Myers, Janssen, and MSD, M. Rodíguez-Gómez: None declared, Paloma Vela-Casasempere: None declared, Alina Boteanu: None declared, J. Narváez: None declared, Victor Martinez Taboada: None declared, Blanca Hernández-Cruz Speakers bureau: Abbvie, Lilly, Sanofi, BMS, STADA, José Luis Andreu: None declared, José A Hernandez Beriain: None declared, Lorena Expósito: None declared, Raúl Menor-Almagro: None declared, Mónica Ibañez Barceló: None declared, Ivan Castellví Consultant of: Boehringer Ingelheim, Actelion, Kern Pharma, Speakers bureau: Boehringer Ingelheim, Actelion, Bristol-Myers Squibb, Roche, Carles Galisteo: None declared, Enrique Raya: None declared, Víctor Quevedo Vila: None declared, Tomas Vazquez Rodriguez: None declared, Jesus Ibañez: None declared, Jose M Pego-Reigosa: None declared

Limit tolerances for sums of measurement errors

2018 ◽  
Vol 934 (4) ◽  
pp. 59-62
Author(s):  
V.I. Salnikov
Keyword(s):  
Normal Distribution ◽  
Mean Square Error ◽  
Gaussian Distribution ◽  
Measurement Errors ◽  
Theory And Practice ◽  
Mean Square ◽  
The Mean ◽  
Limiting Values ◽  
Limiting Value

The question of calculating the limiting values of residuals in geodesic constructions is considered in the case when the limiting value for measurement errors is assumed equal to 3m, ie ∆рred = 3m, where m is the mean square error of the measurement. Larger errors are rejected. At present, the limiting value for the residual is calculated by the formula 3m√n, where n is the number of measurements. The article draws attention to two contradictions between theory and practice arising from the use of this formula. First, the formula is derived from the classical law of the normal Gaussian distribution, and it is applied to the truncated law of the normal distribution. And, secondly, as shown in [1], when ∆рred = 2m, the sums of errors naturally take the value equal to ?pred, after which the number of errors in the sum starts anew. This article establishes its validity for ∆рred = 3m. A table of comparative values of the tolerances valid and recommended for more stringent ones is given. The article gives a graph of applied and recommended tolerances for ∆рred = 3m.

Gingival Health of Porcelain Laminate Veneered Teeth: A Retrospective Assessment

2019 ◽  
Vol 44 (5) ◽  
pp. 452-458 ◽  
Author(s):  
R Arif ◽  
JB Dennison ◽  
D Garcia ◽  
P Yaman
Keyword(s):  
Repeated Measures ◽  
Gingival Crevicular Fluid ◽  
Statistical Significance ◽  
Fluid Collection ◽  
Gingival Recession ◽  
Gingival Health ◽  
Long Term Effect ◽  
The Mean ◽  
Crevicular Fluid

SUMMARY Statement of Problem: The long-term effect of the presence of porcelain laminate veneers (PLVs) on the health of the surrounding gingival issues is not available in the restorative literature. Purpose: To assess the long-term effect of PLVs on the health of the surrounding gingival tissues. A secondary aim was to correlate gingival crevicular fluid (GCF) scores with clinical parameters used for gingival health assessment in teeth treated with PLVs. Methods and Materials: Patients who received PLVs placed at the Graduate Restorative Clinic within a seven- to 14-year period were recalled for clinical evaluations. Periodontal measurements including gingival index (GI), periodontal pocket depth (PPD), gingival recession (GR), and clinical attachment level (CAL) were measured using a standard probe and indices. Gingival Crevicular Fluid (GCF) was measured with a Periotron machine (Periotron 8000, Oraflow Inc), using Periopaper (Periopaper Gingival Fluid Collection Strip, Oraflow Inc.) for fluid collection. Photographs of any observed clinical defect were taken. Data were tabulated using Excel 2010 (Microsoft Corp). Statistical analysis for all descriptive statistics was performed using SPSS 21 (SPSS Software, IBM Corp.) and Stata SE 13 (Stata Software, StataCorp). Repeated-measures analysis of variance (ANOVA) was done to test for statistical significance of the mean pocket depths between the restored and unrestored surfaces of the veneered teeth. The significance level for all tests was p<0.05. Pearson's correlation coefficient was performed for testing statistical significance between GCF and GI and between GCF and PPD. Results: The frequency distribution of the GI included 47 PLVs (43%) with normal gingiva, 16 (15%) with mild inflammation, and 46 (42%) with moderate inflammation and bleeding on probing. The average PPD on the facial surface of the maxillary and mandibular PLVs was 2.17 mm and 2.16 mm, respectively. On the lingual surface, the average PPD was 2.10 mm for maxillary and 2.22 mm for mandibular PLVs. Gingival recession was seen in 27% of the evaluated PLVs. The repeated-measures ANOVA revealed p≥0.136, showing no statistical difference in the mean pocket depths between restored facial and unrestored lingual surfaces of the veneered teeth. A moderate correlation (r=0.407) was found between GCF and GI, which was significant at p<0.001. No correlation (r=0.124) was found between GCF and PPD, which was not significant at p=0.197. Conclusions: Gingival response to the evaluated PLVs was in the satisfactory range, with overall GI scores ranging between normal and moderate inflammation, pocket depths ranging from 1 to 2 mm, and recession present in 27% of the evaluated PLVs. No statistically significant difference was found between the mean pocket depths of the restored and unrestored surfaces of veneered teeth (p≥0.136). A moderate correlation was found between GCF and GI.

scholarly journals Higher Caloric Refeeding Is Safe in Hospitalised Adolescent Patients with Restrictive Eating Disorders

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Elizabeth K. Parker ◽  
Sahrish S. Faruquie ◽  
Gail Anderson ◽  
Linette Gomes ◽  
Andrew Kennedy ◽  
...  
Keyword(s):  
Eating Disorders ◽  
Weight Gain ◽  
Statistical Significance ◽  
Caloric Intake ◽  
Tube Feeding ◽  
Retrospective Chart Review ◽  
Refeeding Syndrome ◽  
Restrictive Eating ◽  
Weight Restoration ◽  
The Mean

Introduction. This study examines weight gain and assesses complications associated with refeeding hospitalised adolescents with restrictive eating disorders (EDs) prescribed initial calories above current recommendations.Methods. Patients admitted to an adolescent ED structured “rapid refeeding” program for >48 hours and receiving ≥2400 kcal/day were included in a 3-year retrospective chart review.Results. The mean (SD) age of the 162 adolescents was 16.7 years (0.9), admission % median BMI was 80.1% (10.2), and discharge % median BMI was 93.1% (7.0). The mean (SD) starting caloric intake was 2611.7 kcal/day (261.5) equating to 58.4 kcal/kg (10.2). Most patients (92.6%) were treated with nasogastric tube feeding. The mean (SD) length of stay was 3.6 weeks (1.9), and average weekly weight gain was 2.1 kg (0.8). No patients developed cardiac signs of RFS or delirium; complications included 4% peripheral oedema, 1% hypophosphatemia (<0.75 mmol/L), 7% hypomagnesaemia (<0.70 mmol/L), and 2% hypokalaemia (<3.2 mmol/L). Caloric prescription on admission was associated with developing oedema (95% CI 1.001 to 1.047;p=0.039). No statistical significance was found between electrolytes and calories provided during refeeding.Conclusion. A rapid refeeding protocol with the inclusion of phosphate supplementation can safely achieve rapid weight restoration without increased complications associated with refeeding syndrome.

scholarly journals Prospective Analysis of Coagulopathy Associated with Isolated Traumatic Brain Injury and Clinical Outcome

2021 ◽  
Author(s):  
Gopal Krishna ◽  
Varun Aggarwal ◽  
Ishwar Singh
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Head Injury ◽  
Clinical Outcome ◽  
Road Traffic ◽  
Statistical Significance ◽  
Platelet Counts ◽  
Coagulation Abnormalities ◽  
The Mean ◽  
D Dimer

Abstract Introduction Traumatic brain injury (TBI) affects the coagulation pathway in a distinct way than does extracranial trauma. The extent of coagulation abnormalities varies from bleeding diathesis to disseminated thrombosis. Design Prospective study. Methods The study included 50 patients of isolated TBI with cohorts of moderate (MHI) and severe head injury (SHI). Coagulopathy was graded according to the values of parameters in single laboratory. The incidence of coagulopathy according to the severity of TBI and correlation with disseminated intravascular coagulation (DIC) score, platelets, prothrombin time (PT), activated partial thromboplastin time (APTT), D-dimer, and fibrinogen was observed. The comparison was also made between expired and discharged patients within each group. It also compared coagulation derailments with clinical presentation (Glasgow Coma Scale [GCS]) and outcome (Glasgow Outcome Scale [GOS]). Results Road traffic accident was the primary (72%) mode of injury. Fifty-two percent had MHI and rest had SHI. Eighty-four percent of cases were managed conservatively. The mean GCS was 12.23 and 5.75 in MHI and SHI, respectively. Sixty-two percent of MHI and 96% of the patients with SHI had coagulation abnormalities. On statistical analysis, DIC score (p < 0.001) strongly correlated with the severity of head injury and GOS. PT and APTT were also significantly associated with the severity of TBI. In patients with moderate TBI, D-dimer and platelet counts showed association with clinical outcome. Fibrinogen levels did not show any statistical significance. The mean platelet counts remained normal in both the groups of TBI. The mean GOS was 1.54 and 4.62 in SHI and MHI, respectively. Conclusion Coagulopathy is common in isolated TBI. The basic laboratory parameters are reliable predictors of coagulation abnormalities in TBI. Coagulopathy is directly associated with the severity of TBI, GCS, and poor outcome.

scholarly journals POS1281 HOW DOES OBESITY INFLUENCE THE FEATURES OF KNEE OSTEOARTHRITIS?

2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 923.4-924
Author(s):  
H. Hachfi ◽  
D. Khalifa ◽  
M. Brahem ◽  
N. Ben Chekaya ◽  
M. Younes
Keyword(s):  
Knee Osteoarthritis ◽  
Functional Impairment ◽  
Statistical Significance ◽  
Obese Group ◽  
University Hospital ◽  
Obese Patients ◽  
Cross Sectional ◽  
Duration Of Symptoms ◽  
Lequesne Index ◽  
The Mean

Background:Knee osteoarthritis and obesity are both major health problems. It is now admitted that the prevalence of knee osteoarthritis gets higher with obesity and that weight loss helps knee function and allows patients to avoid surgery.Objectives:The aim of this study was to study the influence of obesity on knee osteoarthritis features.Methods:A cross-sectional study was conducted in the university hospital Taher Sfar of Tunisia over a period of 6 months. Patients who had knee osteoarthritis confirmed by radiographs were included. Sociodemographic, clinical, radiological and therapeutic data were collected from medical records and visits. Obesity was defined by a body mass index (BMI) ≥30. Functional impairment was assessed by the Womac index and Lequesne index.Results:The study included 186 patients. There were 31 males and 155 femmes. The mean age was 60±10 years. The percentage of obese patients was 53,8%. The mean age was similar in both groups obese and non obese. There were more women in the obese group compared to the non obese group (p=0.0001), more patients who had diabetes mellitus and dyslipidemia (p=0.002). Non-obese patients had a shorter duration of symptoms with no statistical significance (p=0.151). Obese patients had more involvement of both knees (p<0.0001). Obesity did not have an impact on pain severity. Severity of radiological images (p=0,0001) were more frequent in obese patients. Functional impairment was similar in both groups. However, the percentage of patients having a very important functional impairment with Lequesne index was higher in obese patients (p<0.029). Obese patients also needed more physical therapy sessions (p=0.035).Conclusion:Knee osteoarthritis in obese patients is characterized with the femlae gender predominance, bilateral knee involvement, and a more severe images on radiographs. Thus the need for better control of weight and the importance of physical activity.References:[1]Coggon D, Reading I, Croft P, et al. Knee osteoarthritis and obesity. Int J Obes Relat Metab Disord J Int Assoc Study Obes 2001; 25: 622–627.Disclosure of Interests:None declared

Prognostic value of the cardiorespiratory optimal point during submaximal exercise testing

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
J.P Dias Ferreira Reis ◽  
A Goncalves ◽  
P Bras ◽  
V Ferreira ◽  
J Viegas ◽  
...  
Keyword(s):  
Heart Failure ◽  
Primary Endpoint ◽  
Statistical Significance ◽  
Peak Level ◽  
Submaximal Exercise ◽  
Peak Oxygen Consumption ◽  
Optimal Point ◽  
Reduced Ejection Fraction ◽  
Tertiary Center ◽  
The Mean

Abstract Background Peak oxygen consumption (pVO2) is a key parameter in assessing the prognosis of heart failure with reduced ejection fraction (HFrEF) patients (pts). However, it is a less reliable parameter when the cardiopulmonary exercise test (CPET) is not maximal. It is crucial to identify the submaximal exercise variables with the best prognostic power (PP), in order to improve the management of pts that cannot attain a maximal CPET. Purpose The aim of this study was to evaluate and compare the PP of several exercise parameters in submaximal CPET for risk stratification in pts with HFrEF. Methods Prospective evaluation of adult pts with HFrEF submitted to CPET in a tertiary center. A submaximal CPET was defined by a respiratory exchange ratio (RER) ≤1.10. Pts were followed up for at least 1 year for the primary endpoint of cardiac death and urgent heart transplantation/ ventricular assist device implantation. Several CPET parameters were analyzed as potential predictors of the combined endpoint and their PP (area under the curve - AUC) was compared to that of pVO2, using the Hanley and McNeil test. Results CPET was performed in 487 HF pts, of which 317 (66%) performed a submaximal CPET. Pts averaged 57±12 years of age, 77% were male, 45.7% had ischemic cardiomyopathy, with a mean LVEF of 30.4±7.6%, a mean heart failure survival score of 8.6±1.1. The mean pVO2 was 17.1±5.5 ml/kg/min and the mean RER 1.01±0.08. During a mean follow-up (FU) time of 11±1 months, 18 pts (6%) met the primary endpoint. Cardiorespiratory optimal point (OP - VE/VO2) had the highest AUC value (0.915, p=0.001), followed by the partial pressure of end-tidal CO2 at the anaerobic threshold - PETCO2L (0.814, p&lt;0.001). pVO2 presented an AUC of 0.730 (p=0.001). OP≥31 and PETCO2L ≤37mmHg had a sensitivity of 100 and 76.9% and a specificity of 71.1 and 67%, respectively, for the primary outcome. OP presented a significantly higher PP than pVO2 (p=0.048), whether PETCO2L didn't achieve any statistical significance (p=0.164). Pts with anOP≥31 presented a significantly lower survival free of HT during FU (log rank p=0.002). Conclusion OP had the highest PP for HF events of all parameters analyzed for a submaximal CPET. This parameter can help stratify the HF pts physiologically unable to reach a peak level of exercise. Funding Acknowledgement Type of funding source: None

scholarly journals Analysis of Surgical Recurrence after Larynx Microsurgery for Benign Lesions

2020 ◽  
Author(s):  
Maria Theresa Costa Ramos de Oliveira Patrial ◽  
Rogério Hamerschmidt ◽  
Jorge Eduardo Fouto Matias ◽  
Evaldo Dacheux de Macedo Filho ◽  
Bettina Carvalho
Keyword(s):  
Statistical Significance ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Associated Lesions ◽  
Surgical Recurrence ◽  
Retrospective Data Collection ◽  
The Mean ◽  
And Gender ◽  
Benign Laryngeal Lesions ◽  
Reinke Edema

Abstract Introduction The study of larynx lesions is of great importance. More than 50% of people with vocal complaints have benign vocal fold alterations and some require surgery. Objective To determine which factors are related to surgical recurrence of benign laryngeal lesions and to determine which videolaryngoscopic diagnoses are related to the risk or protection of surgical relapses over time. Methods Observational, analytical, cross-sectional study with retrospective data collection of 1,383 surgeries in 1,301 patients. Results The mean age at the first surgery was 39.2 years old. The predominant gender was female (65.6%).There were 396 cases of polyps (25.34%), 349 cases of cysts (22.33%), 261 cases of Reinke edema (16.7%), 175 cases of nodules (11.2%), 153 cases of minor structural alterations (MSAs) (9.79%), 94 cases of leukoplakia (6.01%), 77 cases of granulomas (4.93%) and 58 cases of pseudocysts (3.71%). The age presented statistical significance with the risk of surgical relapses (p = 0.016). Male gender was associated with the greatest chance of relapse.Diagnosis of granuloma (p < 0.001) and of leukoplakia (p < 0.001) were associated with a higher risk of surgical recurrence. Cyst diagnosis was associated with protection (p = 0.015) in relation to the chance of further surgeries. Patients with associated lesions, bilaterals or voice professionals did not present a statistically significant association with surgical recurrence. Conclusion Age and gender are statistically related to the increase of surgical relapses. Leukoplakia and granuloma are associated with increased surgical relapses. Patients submitted to cyst microsurgery appear to be protected against surgical recurrence.

scholarly journals Colonoscopy does not induce small intestinal bacterial overgrowth

2017 ◽  
Vol 08 (01) ◽  
pp. 12-16
Author(s):  
Ioana Gabriela Moraru ◽  
Dan Lucian Dumitraşcu
Keyword(s):  
Statistical Significance ◽  
False Negative ◽  
Bacterial Overgrowth ◽  
Intestinal Bacteria ◽  
Small Intestinal Bacterial Overgrowth ◽  
Mean Value ◽  
Intestinal Bacterial Overgrowth ◽  
Gastrointestinal Pathology ◽  
The Mean ◽  
Small Intestinal

Abstract Background and Aim: Small intestinal bacterial overgrowth (SIBO) is associated with gastrointestinal pathology and colonoscopy. This endoscopic investigation could cause changes in gut flora including the occurrence of SIBO. We looked in this study for the effect of colonoscopy (preparation and intubation) on the occurrence of SIBO. Materials and Methods: Prospective study including thirty patients with irritable bowel syndrome (IBS) diagnosed according to Rome III criteria. Two groups were designed: Twenty IBS patients that performed colonoscopy (G1) and ten IBS patients (G2) not referred to colonoscopy. All patients have been tested for the presence of SIBO using glucose hydrogen breath tests (GHBT) at the beginning of the study, on day 1. G1 patients have also been tested before colonoscopy (day 2) and 1 week after (day 9). G2 patients performed GHBT on day 1 and on day 9. Results: The peak value of expired H2 was assessed, and the mean value was calculated. There were no significant statistical differences between the mean H2 values in the 2 groups of patients on day 1. The mean level of H2 significantly decreased after preparing for colonoscopy in G1 patients (P < 0.0001). There were no significant statistical differences between the mean levels of H2 on day 2 versus day 9 in G1 patients (P = 0.176). The mean level of H2 1 week after performing colonoscopy (7.65 ppm) is higher than that obtained after preparing for it (6.3 ppm), but no statistical significance. Patients from G2 showed no statistical differences between the mean levels of H2 on day 1 versus day 9 (P = 0.6132). Patients in G1 had a significantly lower mean H2 level versus G2 patients on day 9. Conclusions: Colonoscopy does not produce SIBO. Preparing for colonoscopy influences the level of expired H2, it reduces the number of intestinal bacteria, probably trough a mechanic effect or by inflating air during the procedure. Performing GHBT too soon after colonoscopy might result in false negative results of GHBT.

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