Browsing by Author "Cantor, Scott B."

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    Accuracy of optical spectroscopy for the detection of cervical intraepithelial neoplasia without colposcopic tissue information; a step toward automation for low resource settings
    (Society of Photo-Optical Instrumentation Engineers, 2012-04) Yamal, Jose-Miguel; Zewdie, Getie A.; Cox, Dennis D.; Atkinson, E. Neely; Cantor, Scott B.; MacAulay, Calum; Davies, Kalatu; Adewole, Isaac; Buys, Timon P. H.; Follen, Michele
    Optical spectroscopy has been proposed as an accurate and low-cost alternative for detection of cervical intraepithelial neoplasia. We previously published an algorithm using optical spectroscopy as an adjunct to colposcopy and found good accuracy (sensitivity ¼ 1.00 [95% confidence interval ðCIÞ ¼ 0.92 to 1.00], specificity ¼ 0.71 [95% CI ¼ 0.62 to 0.79]). Those results used measurements taken by expert colposcopists as well as the colposcopy diagnosis. In this study, we trained and tested an algorithm for the detection of cervical intraepithelial neoplasia (i.e., identifying those patients who had histology reading CIN 2 or worse) that did not include the colposcopic diagnosis. Furthermore, we explored the interaction between spectroscopy and colposcopy, examining the importance of probe placement expertise. The colposcopic diagnosis-independent spectroscopy algorithm had a sensitivity of 0.98 (95% CI ¼ 0.89 to 1.00) and a specificity of 0.62 (95% CI ¼ 0.52 to 0.71). The difference in the partial area under the ROC curves between spectroscopy with and without the colposcopic diagnosis was statistically significant at the patient level (p ¼ 0.05) but not the site level (p ¼ 0.13). The results suggest that the device has high accuracy over a wide range of provider accuracy and hence could plausibly be implemented by providers with limited training.
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    An Alternative Approach for Estimating the Accuracy of Colposcopy in Detecting Cervical Precancer
    (Public Library of Science, 2015) Davies, Kalatu R.; Cantor, Scott B.; Cox, Dennis D.; Follen, Michele
    Introduction: Since colposcopy helps to detect cervical cancer in its precancerous stages, as new strategies and technologies are developed for the clinical management of cervical neoplasia, precisely determining the accuracy of colposcopy is important for characterizing its continued role. Our objective was to employ a more precise methodology to estimate of the accuracy of colposcopy to better reflect clinical practice. Study design: For each patient, we compared the worst histology result among colposcopically positive sites to the worst histology result among all sites biopsied, thereby more accurately determining the number of patients that would have been underdiagnosed by colposcopy than previously estimated. Materials and Methods: We utilized data from a clinical trial in which 850 diagnostic patients had been enrolled. Seven hundred and ninety-eight of the 850 patients had been examined by colposcopy, and biopsy samples were taken at colposcopically normal and abnormal sites. Our endpoints of interest were the percentages of patients underdiagnosed, and sensitivity and specificity of colposcopy. Results: With the threshold of low-grade squamous intraepithelial lesions for positive colposcopy and histology diagnoses, the sensitivity of colposcopy decreased from our previous assessment of 87.0% to 74.0%, while specificity remained the same. The drop in sensitivity was the result of histologically positive sites that were diagnosed as negative by colposcopy. Thus, 28.4% of the 798 patients in this diagnostic group would have had their condition underdiagnosed by colposcopy in the clinic. Conclusions: In utilizing biopsies at multiple sites of the cervix, we present a more precise methodology for determining the accuracy of colposcopy. The true accuracy of colposcopy is lower than previously estimated. Nevertheless, our results reinforce previous conclusions that colposcopy has an important role in the diagnosis of cervical precancer.
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    Cost-effectiveness analysis of a low-cost bubble CPAP device in providing ventilatory support for neonates in Malawi - a preliminary report
    (BioMed Central, 2014) Chen, Ariel; Deshmukh, Ashish A.; Richards-Kortum, Rebecca; Molyneux, Elizabeth; Kawaza, Kondwani; Cantor, Scott B.; Institute for Global Health Technologies
    A low-cost bubble continuous positive airway pressure (bCPAP) device has been shown to be an excellent clinical alternative to nasal oxygen for the care of neonates with respiratory difficulty. However, the delivery of bCPAP requires more resources than the current routine care using nasal oxygen. We performed an economic evaluation to determine the cost-effectiveness of a low-cost bCPAP device in providing ventilatory support for neonates in Malawi. We used patient-level clinical data from a previously published non-randomized controlled study. Economic data were based on the purchase price of supplies and equipment, adjusted for shelf life, as well as hospital cost data from the World Health Organization. Costs and benefits were discounted at 3%. The outcomes were measured in terms of cost, discounted life expectancy, cost/life year gained and net benefits of using bCPAP or nasal oxygen. The incremental cost-effectiveness ratio and incremental net benefits determined the value of one intervention compared to the other. Subgroup analysis on several parameters (birth weight categories, diagnosis of respiratory distress syndrome, and comorbidity of sepsis) was conducted to evaluate the effect of these parameters on the cost-effectiveness. Nasal oxygen therapy was less costly (US$29.29) than the low-cost bCPAP device ($57.78). Incremental effectiveness associated with bCPAP was 6.78 life years (LYs). In the base case analysis, the incremental cost-effectiveness ratio for bCPAP relative to nasal oxygen therapy was determined to be $4.20 (95% confidence interval, US$2.29–US$16.67) per LY gained. The results were highly sensitive for all tested subgroups, particularly for neonates with birth weight 1– < 1.5 kg, respiratory distress syndrome, or comorbidity of sepsis; these subgroups had a higher probability that bCPAP would be cost effective. The bCPAP is a highly cost-effective strategy in providing ventilatory support for neonates in Malawi.
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    Prediction using hierarchical data: Applications for automated detection of cervical cancer
    (Wiley, 2015) Yamal, Jose-Miguel; Guillaud, Martial; Atkinson, E. Neely; Follen, Michele; MacAulay, Calum; Cantor, Scott B.; Cox, Dennis D.
    Although the Papanicolaou smear has been successful in decreasing cervical cancer incidence in the developed world, there exist many challenges for implementation in the developing world. Quantitative cytology, a semi-automated method that quantifies cellular image features, is a promising screening test candidate. The nested structure of its data (measurements of multiple cells within a patient) provides challenges to the usual classification problem. Here we perform a comparative study of three main approaches for problems with this general data structure: (i) extract patient-level features from the cell-level data, (ii) use a statistical model that accounts for the hierarchical data structure, and (iii) classify at the cellular level and use an ad hoc approach to classify at the patient level. We apply these methods to a dataset of 1728 patients, with an average of 2600 cells collected per patient and 133 features measured per cell, predicting whether a patient had a positive biopsy result. The best approach we found was to classify at the cellular level and count the number of cells that had a posterior probability greater than a threshold value, with estimated 61% sensitivity and 89% specificity on independent data. Recent statistical learning developments allowed us to achieve high accuracy.