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Concept: Mann–Whitney U


The purpose of this study was to evaluate the visual outcome of chronic occupational exposure to a mixture of organic solvents by measuring color discrimination, achromatic contrast sensitivity and visual fields in a group of gas station workers. We tested 25 workers (20 males) and 25 controls with no history of chronic exposure to solvents (10 males). All participants had normal ophthalmologic exams. Subjects had worked in gas stations on an average of 9.6 ± 6.2 years. Color vision was evaluated with the Lanthony D15d and Cambridge Colour Test (CCT). Visual field assessment consisted of white-on-white 24-2 automatic perimetry (Humphrey II-750i). Contrast sensitivity was measured for sinusoidal gratings of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0 and 20.0 cycles per degree (cpd). Results from both groups were compared using the Mann-Whitney U test. The number of errors in the D15d was higher for workers relative to controls (p<0.01). Their CCT color discrimination thresholds were elevated compared to the control group along the protan, deutan and tritan confusion axes (p<0.01), and their ellipse area and ellipticity were higher (p<0.01). Genetic analysis of subjects with very elevated color discrimination thresholds excluded congenital causes for the visual losses. Automated perimetry thresholds showed elevation in the 9°, 15° and 21° of eccentricity (p<0.01) and in MD and PSD indexes (p<0.01). Contrast sensitivity losses were found for all spatial frequencies measured (p<0.01) except for 0.5 cpd. Significant correlation was found between previous working years and deutan axis thresholds (rho = 0.59; p<0.05), indexes of the Lanthony D15d (rho=0.52; p<0.05), perimetry results in the fovea (rho= -0.51; p<0.05) and at 3, 9 and 15 degrees of eccentricity (rho= -0.46; p<0.05). Extensive and diffuse visual changes were found, suggesting that specific occupational limits should be created.

Concepts: Mann–Whitney U, Non-parametric statistics, Vision, Visual perception, Visual system, Ophthalmology, Visual field, Ellipse


BACKGROUND: Antibody opsonization of Plasmodium falciparum-infected erythrocytes (IE) plays a crucial role in anti-malarial immunity by promoting clearance of blood-stage infection by monocytes and macrophages. The effects of phagocytosis of opsonized IE on macrophage proinflammatory cytokine responses are poorly understood. METHODS: Phagocytic clearance, cytokine response and intracellular signalling were measured using IFN-gamma-primed human monocyte-derived macrophages (MDM) incubated with opsonized and unopsonized trophozoite-stage CS2 IE, a chondroitin sulphate-binding malaria strain. Cytokine secretion was measured by bead array or ELISA, mRNA using quantitative PCR, and activation of NF-kappaB by Western blot and electrophoretic mobility shift assay. Data were analysed using the Mann-Whitney U test or the Wilcoxon signed rank test as appropriate. RESULTS: Unopsonized CS2 IE were not phagocytosed whereas IE opsonized with pooled patient immune serum (PPS) were (Phagocytic index (PI)=18.4, [SE 0.38] n=3). Unopsonized and opsonized IE induced expression of TNF, IL-1beta and IL-6 mRNA by MDM and activated NF- kappaB to a similar extent. Unopsonized IE induced secretion of IL-6 (median= 622 pg/ml [IQR=1,250-240], n=9) but no IL-1beta or TNF, whereas PPS-opsonized IE induced secretion of IL-1beta (18.6 pg/mL [34.2-14.4]) and TNF (113 pg/ml [421-17.0]) and increased IL-6 secretion (2,195 pg/ml [4,658-1,095]). Opsonized, but not unopsonized, CS2 IE activated caspase-1 cleavage and enzymatic activity in MDM showing that Fc receptor-mediated phagocytosis activates the inflammasome. MDM attached to IgG-coated surfaces however secreted IL-1beta in response to unopsonized IE, suggesting that internalization of IE is not absolutely required to activate the inflammasome and stimulate IL-1beta secretion. CONCLUSIONS: It is concluded that IL-6 secretion from MDM in response to CS2 IE does not require phagocytosis, whereas secretion of TNF and IL-1beta is dependent on Fcgamma receptor-mediated phagocytosis; for IL-1beta, this occurs by activation of the inflammasome. The data presented in this paper show that generating antibody responses to blood-stage malaria parasites is potentially beneficial both in reducing parasitaemia via Fcgamma receptor-dependent macrophage phagocytosis and in generating a robust pro-inflammatory response.

Concepts: Immune system, Inflammation, Antibody, Phagocytosis, Apoptosis, Mann–Whitney U, Non-parametric statistics, Opsonin


Obesity has been associated with respiratory complications, and the majority of these complications occur in the Post-Anesthesia Care Unit (PACU). The aim of this study was to evaluate the outcome and incidence of adverse respiratory events (AREs) in obese patients during their stay in the PACU METHODS: We conducted a prospective control study that included 27 obese patients matched with an equal number of patients with body mass index (BMI)<30 (non-obese control group); the 2 groups of patients were similar in respect to gender distribution, age, and type of surgery and had been admitted into the PACU after elective surgery (May 2011). The AREs were identified during PACU stay. Descriptive analysis of variables was performed, and the Mann-Whitney U test, Chi-square test, or Fisher's exact test were used for comparisons. Associations with AREs were studied using univariate and multivariate logistic regression models.

Concepts: Statistical tests, Statistics, Body mass index, Mann–Whitney U, Non-parametric statistics, Fisher's exact test, Chi-square test, Categorical data


Context:Clinicians who prescribe levothyroxine (LT4) for hypothyroidism often feel strongly about using a brand-name drug instead of a generic.Objective:The objective of the study was to determine whether Synthroid resulted in better control of congenital hypothyroidism than generic LT4.Design:This was a 5-year retrospective study.Setting:The study was conducted at 1 tertiary care center.Patients:Children who were 0-36 months old with congenital hypothyroidism followed up at our center from 2006 to 2011 were treated with either Synthroid exclusively (35 subjects) or generic LT4 exclusively (27 subjects).Interventions:We recorded the subjects' TSH and free T(4) measurements, how often their LT4 dose was adjusted, and the duration of follow-up.Main Outcome Measure:TSH variance between the groups was measured. Secondary end points were the frequency of LT4 dose changes and the variance in free T4.Results:Using the Wilcoxon rank sum test, there was no difference in TSH SD in the Synthroid group compared with the generic group (median 3.0 vs 2.2, P = .27). Using a linear mixed model, children treated with the generic LT4 had lower TSH estimated SD [1.35 with 95% confidence interval (CI) (1.194, 1.526)] than the Synthroid group [1.66 with 95% CI (1.536, 1.803)]. Similarly, no difference was observed in free T(4) SD between the groups using the Wilcoxon rank sum test (median 0.29 generic vs 0.36 Synthroid, P = .11), but the generic group had lower free T(4) estimated SD than the Synthroid group using the linear mixed model [0.216 with 95% CI (0.187, 0.249) vs 0.298 with 95% CI (0.273,0.326)]. Frequency of LT4 dosing adjustments was similar between the groups, both in total (median 2.0 for generic vs 3.0 for Synthroid, P = .097) and when adjusted for number of TSH checks (ratio 0.25 generic vs 0.31 Synthroid, P = .45).Conclusions:In our study of congenital hypothyroidism, generic LT4 treatment resulted in similar or better control of hypothyroidism compared with Synthroid, as assessed by the clinical outcomes of TSH variance and the frequency of LT4 dosing adjustments.

Concepts: Statistics, Measurement, Mann–Whitney U, Non-parametric statistics, Hypothyroidism, Normal distribution, Wilcoxon signed-rank test, Levothyroxine


Objectives: A wireless, inertial sensor-based system has previously been validated for evaluation of equine lameness. However, threshold values have not been determined for the assessment of responses to flexion tests. The aim of this investigation was to evaluate a sensor-based system for objective assessment of the response to flexion. Methods: Healthy adult horses (n = 17) in work were recruited prospectively. Horses were instrumented with sensors on the head (accelerometer), pelvis (accelerometer) and right forelimb (gyroscope), before trotting in a straight line (minimum 25 strides) for 2 consecutive trials. Sensors measured 1) vertical pelvic movement asymmetry (PMA) for both right and left hindlimb strides and 2) average difference in maximum and minimum pelvic height (PDMax and PDMin) between right and left hindlimb strides in millimetres. A hindlimb was randomly selected for proximal flexion (60 s), after which the horse trotted a minimum of 10 strides. Response to flexion was blindly assessed as negative or positive by an experienced observer. Changes in PMA, PDMax and PDMin between baseline and flexion examinations were calculated for each test. Statistical analysis consisted of a Pearson’s product moment test and linear regression on baseline trials, Mann-Whitney rank sum test for effect of flexion and receiver operator curve (ROC) analysis of test parameters. Results: There was a strong correlation between trials for PMA, PDMin and PDMax measurements (P<0.001). A positive flexion test resulted in a significant increase in PMA (P = 0.021) and PDMax (P = 0.05) only. Receiver-operator curve analysis established cut-off values for change in PMA and PDMax of 0.068 and 4.47 mm, respectively (sensitivity = 0.71, specificity = 0.65) to indicate a positive response to flexion. Conclusions: A positive response to flexion resulted in significant changes to objective measurements of pelvic symmetry. Potential relevance: Findings support the use of inertial sensor systems to objectively assess response to flexion tests. Further investigation is warranted to establish cut-off values for objective assessment of other diagnostic procedures.

Concepts: Statistics, Measurement, Type I and type II errors, Assessment, Psychometrics, Mann–Whitney U, Horse, Maxima and minima


Gastric content is a complex biofluid within the human stomach which has an important role in digestive processes. It is believed that gastric content may be a contributory factor in the development of upper gastro-intestinal diseases. In this work, selected ion flow tube mass spectrometry (SIFT-MS) has been applied to the quantification of volatile organic compounds (VOCs) in the headspace vapor of gastric content samples, which were retrieved from three groups of patients, including those with gastro-esophageal cancer, noncancer diseases of the upper gastro-intestinal tract, and a healthy cohort. Twelve VOCs have been investigated in this study; the following 7 VOCs, acetone, formaldehyde, acetaldehyde, hexanoic acid, hydrogen sulphide, hydrogen cyanide, and methyl phenol, were found to be significantly different between cancer and healthy groups by the Mann-Whitney U test. Receiver operating characteristics (ROC) analysis was applied for the combined VOCs of acetaldehyde, formaldehyde, hydrogen sulphide, and methyl phenol to discriminate cancer patients from healthy controls. The area under the curve (AUC) was 0.9. This result raises the prospect that a VOC profile rather than a single biomarker may be preferable in the molecular-orientated diagnosis of gastro-oseophageal cancer, and this warrants further investigation to assess its potential application as a new diagnostic test.

Concepts: Statistics, Stomach, Mann–Whitney U, Non-parametric statistics, Abdomen, Receiver operating characteristic, Digestion, Volatile organic compound


Motivated by the need of poor and rural Mexico, where the population has limited access to advanced medical technology and services, we have developed a new paradigm for medical diagnostic based on the technology of “Volumetric Electromagnetic Phase Shift Spectroscopy” (VEPS), as an inexpensive partial substitute to medical imaging. VEPS, can detect changes in tissue properties inside the body through non-contact, multi-frequency electromagnetic measurements from the exterior of the body, and thereby provide rapid and inexpensive diagnostics in a way that is amenable for use in economically disadvantaged parts of the world. We describe the technology and report results from a limited pilot study with 46 healthy volunteers and eight patients with CT radiology confirmed brain edema and brain hematoma. Data analysis with a non-parametric statistical Mann-Whitney U test, shows that in the frequency range of from 26 MHz to 39 MHz, VEPS can distinguish non-invasively and without contact, with a statistical significance of p<0.05, between healthy subjects and those with a medical conditions in the brain. In the frequency range of between 153 MHz to 166 MHz it can distinguish with a statistical significance of p<0.05 between subjects with brain edema and those with a hematoma in the brain. A classifier build from measurements in these two frequency ranges can provide instantaneous diagnostic of the medical condition of the brain of a patient, from a single set of measurements. While this is a small-scale pilot study, it illustrates the potential of VEPS to change the paradigm of medical diagnostic of brain injury through a VEPS classifier-based technology. Obviously substantially larger-scale studies are needed to verify and expand on the findings in this small pilot study.

Concepts: Medicine, Epidemiology, Statistics, X-ray, Electromagnetic radiation, Mann–Whitney U, Non-parametric statistics, Frequency


Trochanteric overgrowth is one of the major residual deformities after the treatment of Legg-Calvé-Perthes disease. The present study was designed to determine the predictive factors for trochanteric overgrowth at skeletal maturity in patients with the disease. Medical records and radiographs of 45 Legg-Calvé-Perthes disease patients who were treated with containment therapy at our institution were reviewed retrospectively. Univariate analysis was carried out to determine the predictors for trochanteric overgrowth using the Mann-Whitney U-test for continuous variables and the Pearson test for categorical variables. Independent multivariate predictors were identified using logistic regression analysis. Trochanteric overgrowth, defined as articulotrochanteric distance less than +5 mm, was observed in 10 patients (22%). There was a strong correlation between the final Stulberg outcome and trochanteric overgrowth (P=0.0003). Lateral pillar height was the only statistically significant predictor for trochanteric overgrowth at skeletal maturity in univariate and multivariate analyses. The risk for the development of trochanteric overgrowth was much greater in the lateral pillar C hip (44%) than in the lateral pillar B or B/C hip (10%). For the patients with decreased lateral pillar height, a careful follow-up is necessary to make an early decision of prophylactic epiphyseodesis of the greater trochanter.

Concepts: Scientific method, Regression analysis, Logistic regression, Statistics, Prediction, Multivariate statistics, Mann–Whitney U, Univariate


PURPOSE:: To evaluate the impact of conjunctivochalasis (CCh) and its severity on the ocular surface parameters of glaucoma subjects treated with topical antiglaucomatous medication. MATERIALS AND METHODS:: One hundred patients with the clinical diagnosis of glaucoma were recruited for this study. CCh was graded based on the extent of inferior lid margin involvement as follows: 1=single (temporal) location, 2=two locations (nasal and temporal), and 3=whole lid. For all the subjects, the break-up time (BUT), lissamine green (LG) staining, and Schirmer test (under topical anesthesia) was performed for both eyes. Ocular Surface Disease Index (OSDI) questionnaire scores were also noted for each subject. Student t test, Mann-Whitney U test, and Kruskal-Wallis test was used for statistical evaluations. RESULTS:: Sixty-three subjects had evidence of CCh; 32 had grade 1, 24 had grade 2, 7 had grade 3 CCh, and 37 glaucoma patients had no evidence of CCh. There were significant differences in the BUT scores (7.2±2.7 vs. 10.1±2.4 s, P<0.001), Schirmer values (7.7±3.9 vs. 13.3.±4.0 mm, P<0.001), LG staining score (1.6±1.0 vs. 0.3±0.5, P<0.001), and the OSDI scores (19.4±17.2 vs. 6.7±5.2, P<0.001) between patients who had CCh and those without CCh. The BUT scores and Schirmer test values of patients with grades 2 and 3 CCh were significantly lower than those of grade 1 CCh and those without CCh (P<0.001). The LG grading and OSDI scores were significantly higher in grade 2 and 3 patients as compared with those with grade 1 CCh and those without CCh (P<0.001). CONCLUSIONS:: The functional characteristics of the ocular surface appear to be adversely influenced by the presence and the extent of CCh in glaucoma patients.

Concepts: Statistical tests, Statistics, Grade, Mann–Whitney U, Non-parametric statistics, Receiver operating characteristic, Topical anesthetic, Schirmer's test


PurposeTo assess the change in subfoveal choroidal thickness (SFCT) in central serous chorioretinopathy (CSC) following spontaneous resolution and low-fluence photodynamic therapy (PDT) using the enhanced depth imaging optical coherence tomography (EDI-OCT).MethodsA total of 36 consecutive eyes of 36 patients were included in this retrospective study: 16 eyes with spontaneously resolved CSC and 20 eyes with PDT-treated CSC. Best-corrected visual acuity and SFCT were evaluated at each visit until complete absorption of the subretinal fluid. SFCT of 32 normal subjects were also measured, as the control group. Wilcoxon’s singed-rank test was used to evaluate the effects of spontaneous resolution and PDT. To compare the SFCT of the eyes with resolved CSC with that of the normal eyes, Mann-Whitney U-test with Bonferroni correction was also employed.ResultsSFCT of patients was 459.16±77.50 μm at the baseline, and decreased to 419.31±54.49μm after a spontaneous resolution (P=0.015). However, SFCT was not normalized in comparison with that of the normal subjects (P<0.001). SFCT in PDT group was also reduced from 416.43±74.01 to 349.50±88.99 μm (P<0.001), with no significant difference with the normal value (P=0.087).ConclusionsSFCT in patients with CSC decreased both after spontaneous resolution and low-fluence PDT. However, only in the PDT group, after disappearance of subretinal fluid, did it decrease to that of normal subjects.Eye advance online publication, 4 January 2013; doi:10.1038/eye.2012.273.

Concepts: Optics, Statistical significance, Mann–Whitney U, Non-parametric statistics, Eye, Visual acuity, Ophthalmology, Central serous retinopathy