Sorana D. Bolboacă

Exact Probabilities and Confidence Limits for Binomial Samples: Applied to the Difference between Two Proportions

An exact probabilities method is proposed for computing the confidence limits of medical binomial parameters obtained based on the 2×2 contingency table. The developed algorithm was described and assessed for the difference between two binomial proportions (a bidimensional parameter). The behavior of the proposed method was analyzed and compared to four previously defined methods: Wald and Wilson, with and without continuity corrections. The exact probabilities method proved to be monotonic in computing the confidence limits. The experimental errors of the exact probabilities method applied to the difference between two proportions has never exceeded the imposed significance level of 5%.

Design of Experiments: Useful Orthogonal Arrays for Number of Experiments from 4 to 16

A methodology for the design of an experiment is proposed in order to find asmany schemes as possible with the maximum number of factors with different levels for thesmallest number of experimental runs. An algorithm was developed and homemadesoftware was implemented. The abilities in generation of the largest groups of orthogonalarrays were analyzed for experimental runs of 4, 6, 8, 9, 10, 12, 14, 15, and 16. The resultsshow that the proposed method permits the construction of the largest groups of orthogonalarrays with the maximum number of factors.

Impact of Musculoskeletal Ultrasound in an Outpatient Rheumatology Clinic

To evaluate the impact of musculoskeletal ultrasound (MSUS) as a complementary method to clinical assessment on rapid diagnosis and therapeutic decisions in a busy outpatient rheumatology clinic.

Perineural invasion of the major and minor nerves in laryngeal and hypopharyngeal cancer

OBJECTIVE: To investigate the perineural invasion in patients with squamous cell carcinoma of the larynx and hypopharynx. STUDY DESIGN: A prospective study of patients with laryngeal and hypopharyngeal squamous cell carcinoma who underwent total or partial laryngectomy. METHODS: Patients with squamous cell carcinoma of the larynx and pyriform sinus who underwent laryngectomy between 2002 and 2006 in the ENT Clinic of Cluj-Napoca were investigated for histopathological identification of perineural invasion. RESULTS: The present study included 256 patients. Perineural invasion was present in 86 cases out of the 256. Perineural invasion was detected in the major nerves of only one case out of 219 patients who had undergone total laryngectomy. The difference between the mean disease-free survival of patients with or without perineural invasion of the minor nerves was statistically significant (Mann-Whitney U test, P = 0.000102). The local recurrence rates in the cases with or without perineural invasion were significantly different (log-rank test, P = 0.00001). CONCLUSION: Major nerves do not constitute a way of spreading in the squamous cell carcinoma of the larynx and hypopharynx, whereas minor nerves remain a potential one.

Predictivity approach for quantitative structure-property models. Application for blood-brain barrier permeation of diverse drug-like compounds.

The goal of the present research was to present a predictivity statistical approach applied on structure-based prediction models. The approach was applied to the domain of blood-brain barrier (BBB) permeation of diverse drug-like compounds. For this purpose, 15 statistical parameters and associated 95% confidence intervals computed on a 2 × 2 contingency table were defined as measures of predictivity for binary quantitative structure-property models. The predictivity approach was applied on a set of compounds comprised of 437 diverse molecules, 122 with measured BBB permeability and 315 classified as active or inactive. A training set of 81 compounds (~2/3 of 122 compounds assigned randomly) was used to identify the model and a test set of 41 compounds was used as the internal validation set. The molecular descriptor family on vertices cutting was the computation tool used to generate and calculate structural descriptors for all compounds. The identified model was assessed using the predictivity approach and compared to one model previously reported. The best-identified classification model proved to have an accuracy of 69% in the training set (95%CI [58.53–78.37]) and of 73% in the test set (95%CI [58.32–84.77]). The predictive accuracy obtained on the external set proved to be of 73% (95%CI [67.58–77.39]). The classification model proved to have better abilities in the classification of inactive compounds (specificity of ~74% [59.20–85.15]) compared to abilities in the classification of active compounds (sensitivity of ~64% [48.47–77.70]) in the training and external sets. The overall accuracy of the previously reported model seems not to be statistically significantly better compared to the identified model (~81% [71.45–87.80] in the training set, ~93% [78.12–98.17] in the test set and ~79% [70.19–86.58] in the external set). In conclusion, our predictivity approach allowed us to characterize the model obtained on the investigated set of compounds as well as compare it with a previously reported model. According to the obtained results, the reported model should be chosen if a correct classification of inactive compounds is desired and the previously reported model should be chosen if a correct classification of active compounds is most wanted.

A Study of Genetic Algorithm Evolution on the Lipophilicity of Polychlorinated Biphenyls

The search for multivariate linear regression (MLR) in quantitative structure–property relationships (QSPR) is a hard problem, due to the dimension of the entire search space. A genetic algorithm (GA) was developed and assessed, to select proper descriptors for predicting the octan‐1‐ol/H2O partition coefficient of polychlorinated biphenyls. The GA was implemented as a Windows based FreePascal application with MySQL connectivity for fetching the data. An outcome study based on 30 runs was done keeping all parameters constant: sample size, 8; number of variables in the MLR, 2; adaptation‐imposed requirements; maximum number of generations, 1000; selection strategy, proportional; probability of mutation, 0.05; number of genes implied in mutation, 2; optimization parameter, r2; optimization score, minimum in sample; and optimization objective, maximum. The results revealed that the number of evolutions followed the Poisson distribution with the sample size as parameter. The average of the determination coefficient is higher than 98% of the determination coefficient obtained through complete search, and follows the Gaussian distribution. The correlation coefficients obtained by the best performing GA‐MLR models proved not to be statistically different from the correlation coefficient of the QSPR model obtained by complete search.

Assessment of Cutaneous Melanoma by Use of Very- High-Frequency Ultrasound and Real-Time Elastography

OBJECTIVE The primary objective of this study was to evaluate the usefulness of very-high-frequency ultrasound as tool for assessment of skin melanoma by investigation of the correlation between the ultrasound measurement of the thickness of a melanoma and the histopathologically measured Breslow index. The secondary objective was to assess the potential role of real-time elastography in the preoperative evaluation of skin melanoma. SUBJECTS AND METHODS The study included 42 cutaneous melanoma lesions in 39 adult subjects examined in the division of ultrasound of a department of radiology between September 2011 and January 2015. Gray-scale sonographic features at 40 MHz (thickness, echogenicity, contour) and real-time strain elastographic (qualitative and semiquantitative, strain ratio) characteristics were evaluated and compared with the pathologic results. RESULTS The melanoma lesions had a homogeneous hypoechoic appearance with a regular contour and stiff or medium consistency. The mean difference between Breslow index and ultrasound thickness was -0.05 mm (95% CI, -0.24 to 0.13 mm), sustaining the absence of significant differences between these two measurements. A strong relation was identified between real-time elastographic appearance and strain ratio for the relations between lesion and hypodermis and between lesion and neighboring dermis (p < 0.002) or hypodermis. CONCLUSION Our study showed that very-high-frequency ultrasound and real-time elastography can be useful examinations for comprehensive preoperative evaluation of cutaneous melanoma.

Characteristic and counting polynomials: modelling nonane isomers properties

The major goal of this study was to investigate the broad application of graph polynomials to the analysis of Henrys law constants (solubility) of nonane isomers. In this context, Henrys law constants of nonane isomers were modelled using characteristic and counting polynomials. The characteristic and counting polynomials on the distance matrix (CDi), on the maximal fragments matrix (CMx), on the complement of maximal fragments matrix (CcM) and on the Szeged matrix (CSz) were calculated for each compound. One of the nonane isomers, 4-methyloctane, was identified as an outlier and was withdrawn from further analysis. This report describes the performance and characteristics of most significant models. The results showed that Henrys law constants of nonane isomers could be modelled by using characteristic polynomial and counting polynomial on the distance matrix.

Doppler ultrasound and strain elastography in the assessment of cutaneous melanoma: preliminary results

AIM To study the usefulness of color or power Doppler ultrasound (US) in the pre-surgical evaluation of skin melanoma, and to correlate the Doppler characteristics with the appearance on high frequency ultrasound strain elastography (SE) in the preoperative evaluation of cutaneous melanoma. MATERIALS AND METHOD The study included 42 cutaneous melanoma lesions in 39 adult subjects examined between September 2011 and January 2015. Doppler US features (the presence and aspect of vascularization, and the number of vascular pedicles) and elasticity by strain elastography were evaluated together with the pathological results. RESULTS The melanoma lesions presented hyper-vascularization, with multiple vascular pedicles and stiff appearance. Significant correlations between the thickness of the tumor, measured histopathologically by the Breslow index, and the degree of vascularization (p=0.0167), and number of vascular pedicles (p=0.0065) were identified. Strong correlations between the SE appearance and vascularization on one hand, and SE and the number of vascular pedicles were also identified (p<0.001). CONCLUSION Our study demonstrates that Doppler US and SE offer useful information for THE preoperative evaluation of cutaneous melanoma and may contribute to better defining the long term prognosis.

Sensitivity, specificity, and accuracy of predictive models on phenols toxicity

The investigation of how the influential affect the metrics and predictivity of multiple linear regressions on a set of phenolic compounds with toxicity on Tetrahymena pyriformis is presented. The investigation of influential was conducted using standardized residuals (ri-model) and Cooks distance (Di-model) approaches. The applied approaches let to improvement of models metrics, robustness and accuracy on the investigated sample. Overall, the ri-model proved higher accuracy and robustness in terms of sensitivity while Di-model proved robustness in terms of specificity. Characterization of the withdrawn compounds is essential for advance in developing models for the toxicity of phenols.