Linear regression models and k-means clustering for statistical analysis of fNIRS data

We propose a new algorithm, based on a linear regression model, to statistically estimate the hemodynamic activations in fNIRS data sets. The main concern guiding the algorithm development was the minimization of assumptions and approximations made on the data set for the application of statistical tests. Further, we propose a K-means method to cluster fNIRS data (i.e. channels) as activated or not activated. The methods were validated both on simulated and in vivo fNIRS data. A time domain (TD) fNIRS technique was preferred because of its high performances in discriminating cortical activation and superficial physiological changes. However, the proposed method is also applicable to continuous wave or frequency domain fNIRS data sets.OCIS codes: (000.5490) Probability theory, stochastic processes, and statistics; (170.2655) Functional monitoring and imaging; (170.6920) Time-resolved imaging; (170.1470) Blood or tissue constituent monitoring     

Uncontrolled Web-Based Administration of Surveys on Factual Health-Related Knowledge: A Randomized Study of Untimed Versus Timed Quizzing

Background

Health knowledge and literacy are among the main determinants of health. Assessment of these issues via Web-based surveys is growing continuously. Research has suggested that approximately one-fifth of respondents submit cribbed answers, or cheat, on factual knowledge items, which may lead to measurement error. However, little is known about methods of discouraging cheating in Web-based surveys on health knowledge.

Objective

This study aimed at exploring the usefulness of imposing a survey time limit to prevent help-seeking and cheating.

Methods

On the basis of sample size estimation, 94 undergraduate students were randomly assigned in a 1:1 ratio to complete a Web-based survey on nutrition knowledge, with or without a time limit of 15 minutes (30 seconds per item); the topic of nutrition was chosen because of its particular relevance to public health. The questionnaire consisted of two parts. The first was the validated consumer-oriented nutrition knowledge scale (CoNKS) consisting of 20 true/false items; the second was an ad hoc questionnaire (AHQ) containing 10 questions that would be very difficult for people without health care qualifications to answer correctly. It therefore aimed at measuring cribbing and not nutrition knowledge. AHQ items were somewhat encyclopedic and amenable to Web searching, while CoNKS items had more complex wording, so that simple copying/pasting of a question in a search string would not produce an immediate correct answer.

Results

A total of 72 of the 94 subjects started the survey. Dropout rates were similar in both groups (11%, 4/35 and 14%, 5/37 in the untimed and timed groups, respectively). Most participants completed the survey from portable devices, such as mobile phones and tablets. To complete the survey, participants in the untimed group took a median 2.3 minutes longer than those in the timed group; the effect size was small (Cohen’s r=.29). Subjects in the untimed group scored significantly higher on CoNKS (mean difference of 1.2 points, P=.008) and the effect size was medium (Cohen’s d=0.67). By contrast, no significant between-group difference in AHQ scores was documented. Unexpectedly high AHQ scores were recorded in 23% (7/31) and 19% (6/32) untimed and timed respondents, respectively, very probably owing to “e-cheating”.

Conclusions

Cribbing answers to health knowledge items in researcher-uncontrolled conditions is likely to lead to overestimation of people’s knowledge; this should be considered during the design and implementation of Web-based surveys. Setting a time limit alone may not completely prevent cheating, as some cheats may be very fast in Web searching. More complex and contextualized wording of items and checking for the “findability” properties of items before implementing a Web-based health knowledge survey may discourage help-seeking, thus reducing measurement error. Studies with larger sample sizes and diverse populations are needed to confirm our results.     

Molecular and Serological Diversity of Neisseria meningitidis Carrier Strains Isolated from Italian Students Aged 14 to 22 Years

Neisseria meningitidis is an obligate human commensal that commonly colonizes the oropharyngeal mucosa. Carriage is age dependent and very common in young adults. The relationships between carriage and invasive disease are not completely understood. In this work, we performed a longitudinal carrier study in adolescents and young adults (173 subjects). Overall, 32 subjects (18.5%) had results that were positive for meningococcal carriage in at least one visit (average monthly carriage rate, 12.1%). Only five subjects tested positive at all four visits. All meningococcal isolates were characterized by molecular and serological techniques. Multilocus sequence typing, PorA typing, and sequencing of the 4CMenB vaccine antigens were used to assess strain diversity. The majority of positive subjects were colonized by capsule null (34.4%) and capsular group B strains (28.1%), accounting for 23.5% and 29.4% of the total number of isolates, respectively. The fHbp and nhba genes were present in all isolates, while the nadA gene was present in 5% of the isolates. The genetic variability of the 4CMenB vaccine antigens in this collection was relatively high compared with that of other disease-causing strain panels. Indications about the persistence of the carriage state were limited to the time span of the study. All strains isolated from the same subject were identical or cumulated minor changes over time. The expression levels and antigenicities of the 4CMenB vaccine antigens in each strain were analyzed by the meningococcal antigen typing system (MATS), which revealed that expression can change over time in the same individual. Future analysis of antigen variability and expression in carrier strains after the introduction of the MenB vaccine will allow for a definition of its impact on nasopharyngeal/oropharyngeal carriage.     

A noninvasive index of atrial remodeling in patients with paroxysmal and persistent atrial fibrillation: a pilot study

PurposeThis study aims to develop a noninvasive atrial remodeling index (RI) to separate patients presenting paroxysmal atrial fibrillation (ParAF) from those with sustained persistent atrial fibrillation (PerAF), that is, AF episodes interrupted 7 days or more after the onset.MethodsSignal-averaged P-wave duration (SAPWd) and left atrial anteroposterior diameter (LADd) were measured in 33 ParAF patients, in 26 sustained PerAF patients, and in 18 control subjects. By using SAPWd and LADd, a dichotomous (0/1) RI was created. A logistic regression model on the probability of having a sustained PerAF vs a ParAF episode was estimated, including the RI, sex, age, and cardiac comorbidities as covariates.ResultsSignal-averaged P-wave duration was significantly longer in sustained PerAF (153 ± 15 milliseconds) than in ParAF patients (142 ± 13 milliseconds, P < .001) and in both ParAF and sustained PerAF groups vs control group (123 ± 7 milliseconds, P < .001). Left atrial anteroposterior diameter was larger both in sustained PerAF (43 ± 6 mm) vs ParAF patients (38 ± 5 mm, P = .002) and in sustained PerAF group vs control group (38 ± 2 mm, P = .004), but no differences were observed between ParAF patients and controls (P = .6). A 12-fold increase (odds ratio, 11.8; 95% confidence interval, 2.2-63.5) in the odds of having a sustained PerAF vs a ParAF episode was observed in patients with RI equal to 1.ConclusionsP-wave duration and left atrium diameter enabled to define a noninvasive atrial RI to separate patients with ParAF from those with sustained PerAF. This could be a useful tool to select a suitable strategy for AF treatment.     

A novel, highly sensitive and rapid allele-specific loop-mediated amplification assay for the detection of the JAK2V617F mutation in chronic myeloproliferative neoplasms

Background The identification of the JAK2V617F mutation is mandatory in the diagnostic work-up of Philadelphia chromosome-negative myeloproliferative neoplasms. Several molecular techniques to detect this mutation are currently available, but each of them has some limits. DESIGN AND METHODS: We set up a novel molecular method for the identification of the JAK2V617F mutation based on an allele-specific loop-mediated amplification, not polymerase chain reaction analysis. This innovative technique amplifies DNA targets under isothermal conditions with high specificity, efficiency and rapidity. The method does not require either a thermal cycler or gel separation and the DNA amplification reaction is visible to the naked eye and can be monitored by turbidimetry. This method was validated on DNA from cell lines as well as from patients with myeloproliferative neoplasms. The results were compared with those obtained by conventional polymerase chain reaction methods. RESULTS: This assay detects, within 1 hour, the JAK2V617F mutation down to an allele burden of 0.1-0.01%. All samples positive by polymerase chain reaction (n=146) proved positive when tested by allele-specific loop-mediated amplification and none of the 80 negative controls gave false positive results. In addition, six patients with essential thrombocythemia previously diagnosed as being JAK2V617F negative by polymerase chain reaction analysis were found to be positive (at a low level) by allele-specific loop-mediated amplification. Furthermore, this assay discriminated the amount of JAK2V617F tumor allele within intervals of positivity, above 50%, between 50% and 10% and below 10%. Conclusions Allele-specific loop-mediated amplification is a simple, robust and easily applicable method for the molecular diagnosis and monitoring of JAK2V617F mutation in patients with chronic myeloproliferative neoplasms.     

Left-handedness is statistically linked to lifetime experimentation with illicit drugs

Handedness has been linked to an enhanced risk of alcohol abuse, while less is known about other drugs. A convenience sample of 1004 male and female Italian participants (females=58%) from the general community (18 to 65 years old: average age = 30; standard deviation = 10, median = 25) was asked about: handedness (preference in writing); lifetime use of alcohol, tobacco, and illicit drugs; levels of psychological distress, as measured by the General Health Questionnaire (GHQ); and levels of delusion proneness, as measured by the Peters et al. Delusions Inventory (PDI). Overall, 92 individuals (9.2%) were classified as left-handed, with no significant difference reported among genders. Lifetime use of illicit drugs, primarily cannabis, was reported by 20% of the sample. In a multiple logistic regression analysis, after taking into account sex, age, and caseness on GHQ and PDI, left-handed people in the sample were statistically more likely to report lifetime experimentation with heroin, ecstasy/amphetamine, and, marginally, hallucinogens, but not alcohol or tobacco. Different mechanisms might contribute to an explanation of greater lifetime experimentation with some illicit drugs among left-handed people as compared to right-handed people. However, replications with clinical samples are necessary before any definitive statements can be made.     

A naturalistic study on the criteria of choice of second-generation antidepressants: A comparison of venlafaxine and SSRIs in depressed inpatients

INTRODUCTION: The objective of this study was to compare, in a naturalistic setting, the efficacy and tolerability of selective serotonin reuptake inhibitors (paroxetine, sertraline, citalopram) and venlafaxine, in 120 depressed inpatients. This paper attempts to review which variables may influence a physician's choice of a specific antidepressant for a specific patient. METHOD: Patients were assessed using the Hamilton Psychiatric Rating Scale for Depression (HAM-D), the Montgomery-Åsberg Depression Rating Scale (MADRS), the Clinical Global Impression (CGI) and the Symptoms Check List (SCL-90). The two groups under assessment were comparable in all socio-demographic characteristics. We used logistic regression analyses to identify variables that differentiate the two groups at baseline. This, in turn, would represent those variables with the potential to influence a physician's selection of an antidepressant. RESULTS: Venlafaxine patients reported significantly worse scores on MADRS at baseline, but any difference was no longer present at discharge. We found no significant variation in the efficacy of the antidepressants under study and there were no differences in the incidence and profiles of adverse events between the groups of patients. CONCLUSION: The degree of severity of the actual depressive picture appears to influence choice in favour of venlafaxine. However, it appears that the choice of SSRIs is more closely linked to patients who present a previous history of non-mood psychiatric symptoms.