Biomedical subjects

Deborah Thompson

Publications and source records attributed to Deborah Thompson.

42 records · Page 3Linked to original sources

PubMed2002

Improving inter-observer agreement and certainty level in diagnosing and grading papillary urothelial neoplasms: usefulness of a Bayesian belief network.

BACKGROUND AND OBJECTIVE: A Bayesian belief network (BBN), as diagnostic decision support system, enables the processing of our knowledge of histopathology expressed in descriptive terms, words and concepts. The aim of this study was to evaluate the contribution of a BBN in the improvement of inter-observer agreement and certainty level in the diagnosis and grading of papillary urothelial neoplasms. MATERIALS: Inter-observer agreement and certainty level were investigated on 40 cases of non-invasive papillary urothelial neoplasms subdivided according to the WHO 1973 classification. There were 10 urothelial papillomas (UPs), 10 grade 1 papillary carcinomas (G1), 10 grade 2 papillary carcinomas (G2) and 10 grade 3 papillary carcinomas (G3). Five consecutive sessions were held with three observers (RMa, PC and MSt). Sessions A, B and D were based on the morphological evaluation of the specimens with a conventional light microscope only. In sessions C and E, a BBN was used in addition to the microscope. The BBN output was represented by four belief values for four possible diagnostic outcomes. These values ranged from 0.0 to 1.0, with the sum of the belief values being 1.0. Concerning the certainty level, a two-tier system of assessment was adopted in sessions A, B and D: certain versus less certain. In sessions C and E, a belief value equal to or greater than 0.65 was considered as equivalent to "certain". RESULTS: In session A, an all-encompassing or synthetic approach to decision-making was adopted. Agreement with the gold standard was seen in 60% (RMa), 55% (PC) and 65% (MSt) of cases, respectively. The level of subjective confidence was "certain" in 35%, 40% and 35% of cases, respectively. Better agreement-70% (RMa), 68% (PC) and 72% (MSt) of cases-was present in session B where an analytical approach based on the evaluation of a series of morphological features was used. The level of subjective confidence was "certain" in 45%, 50% and 55% of cases, respectively. In session C, where a BBN was utilised, a further increase in degree of agreement with the gold standard was observed, e.g. 85% (RMa), 80% (PC) and 86% (MSt) of cases, respectively. Levels of certainty or belief values were high. Decrease in both the level of agreement-60% (RMa), 62% (PC) and 65% (MSt) of cases-and certainty was seen in session D where the observers were left free to evaluate the cases morphologically without the constrain of either a synthetic or analytical approach. In session E, where the BBN was used again, the percentage of cases in agreement with the gold standard increased to 83% (RMa), 81% (PC) and 84% (MSt), respectively. Increase in certainty or belief was also seen. The difference of the results obtained in the sessions A, B and D with those seen in the BBN-based sessions (C and E) is statistically significant. CONCLUSIONS: Conventional morphological evaluation of papillary urothelial neoplasms is affected by inter-observer variability and, in many instances, by diagnostic uncertainty. The greatest difficulties are found with G1 and G2 cases. Improvement in inter-observer agreement and certainty level can be achieved with a BBN.

Bayes Theorem↗

PubMed2002

What is the recall rate of breast MRI when used for screening asymptomatic women at high risk?

Breast screening acceptability is dependent on sensitivity and recall rate. We aimed to establish the recall rate for MRI and mammography, separately and together, when screening a cohort of women at high genetic risk. Women aged 35-49 years in the MARIBS study form the cohort. We analysed the recall rate, the number of extra tests and their effectiveness. Wilcoxon Rank test was used to estimate the effect of age and logistic regression with robust variance the effect of mammographic density on recall rates. The first 726 screening studies took place in 415 women. Following 86 of these recall occurred, comprising 140 additional investigations. 28 of the cases were resolved without further MRI, and 18 women had more than 2 additional tests. Neither age nor mammographic density was associated with recall. MRI had a recall of rate of 10.19%, and mammography 4.00%. The two techniques largely recalled different cases and 10 cases only (11.62% of those recalled) were abnormal by both tests. The two together had a recall rate of 11.85%. Recall rates varied widely between centres of the study. Breast MRI in asymptomatic high-risk women age 35-49 years largely recalls different women from mammography. The combined figure of approximately 12% may be acceptable for screening and will be useful for planning similar studies.

Adult↗

PubMed2002

Variation in BRCA1 cancer risks by mutation position.

Previous studies have reported variation in BRCA1 breast and ovarian cancer risks with mutation position, suggesting that mutations toward the 3' end of the gene are associated with lower ovarian cancer risks. We evaluated the evidence for genotype-phenotype correlations in 356 families with protein-truncating BRCA1 mutations. In contrast to previous reports, the ovarian:breast cancer ratio associated with mutations in a central region of the gene (nucleotides 2401-4190) was significantly higher than for other mutations [odds ratio, 1.70 (P = 0.017) compared with nucleotides 1-2400; odds ratio, 1.89 (P = 0.02) compared with nucleotides 4191-end]. The risks of breast and ovarian cancer conferred by mutations in different regions of the gene were estimated separately by conditional maximum likelihood. According to the best fitting model, the breast cancer risk associated with mutations in the central region was found to be significantly lower than for other mutations (relative risk, 0.71; 95% confidence interval, 0.58-0.86; P = 0.0002), whereas the ovarian cancer risk associated with mutations 3' to nucleotide 4191 was significantly reduced relative to the rest of the gene (relative risk, 0.81; 95% confidence interval, 0.66-1.00; P = 0.044). The cancer risks associated with missense mutations in the RING domain in exon 5 appear to be similar to those associated with protein-truncating mutations toward the 3' end of BRCA1, based on nine additional families.

Aged↗

PubMed2002

Karyometry in endometrial adenocarcinoma of different grades.

OBJECTIVE: To characterize nuclei from adenocarcinoma of the endometrium of different grades in order to establish whether significantly different nuclear subpopulations exist. STUDY DESIGN: A total of 1,400 nuclei from 14 cases of adenocarcinoma of the endometrium of grades 1, 2 and 3 were recorded, and 600 nucleifrom normal, secretory phase glandular endometrial epithelium were used as a reference data set. Karyometric features were computed and a discriminant function derived to define a trend in feature values for nuclei from lesions of different grades. The nuclei from lesions of different grades were processed by a nonsupervised learning algorithm in an effort to detect and define subpopulations. RESULTS: Nuclei from grade 1 lesions represented a near-diploid stemline, whereas nuclei from grade 3 lesions formed an aneuploid set with a mode around 3N. The existence of three subpopulations with statistically different nuclear chromatin patterns could be shown for nuclei from each grade. In each grade these three subpopulations occupied the same relative position in feature space. For grade 1 lesions all three subpopulations were near diploid, for grade 3 lesions all three were approximately triploid. CONCLUSION: The nuclei in adenocarcinoma of the endometrium form a heterogeneous set, with subpopulations of distinctly different chromatin patterns and different ploidy. This should be taken into consideration in assessing the efficacy of chemopreventive intervention.

Adenocarcinoma↗

PubMed2002

Statistical analysis of chemopreventive efficacy of vitamin A in sun-exposed, normal skin.

OBJECTIVE: To develop numeric, statistically secured measures of chemopreventive efficacy and to derive procedures with high sensitivity of detection. STUDY DESIGN: Karyometric features were computed for nuclei from the basal cell layer of biopsies taken from sun-exposed but histologically "normal" skin. Biopsies were collected from placebo-treated subjects and subjects treated for one year with daily, oral doses of 25,000, 50,000 and 75,000 IU of vitamin A. A total of 22,600 nuclei were recorded from 113 cases, at baseline and after one year. RESULTS: Two numeric measures of chemopreventive efficacy were applied: a measure of nuclear abnormality and a measure based on discriminant function scores. Both showed statistically significant chemopreventive effects of vitamin A. Dose-response curves were derived. A novel procedure, second order discriminant analysis, resulted in very high sensitivity for the detection of change in nuclear chromatin patterns. CONCLUSION: Karyometric analysis has increased in sensitivity such that changes on the order of 10%, found in only a low percentage of nuclei in a biopsy specimen, can be reliably documented. The methodology lends itself to cost-efficient screening of compounds for chemopreventive efficacy.

Biopsy↗

PubMedDate not supplied

School-based obesity prevention: a blueprint for taming the epidemic.

OBJECTIVE: To review the literature on school-based obesity prevention programs to identify what can be done to minimize the increasing levels of obesity. METHODS: Twenty articles reporting school-based dietary or physical activity change programs were identified that used BMI or skinfolds as part of the evaluation. RESULTS: Seven studies obtained change in BMI and differed from those not finding change in 3 ways: program implementers were not classroom teachers; intervention targeted middle or high schools; and inactivity reduction was promoted. CONCLUSIONS: An 8-step research strategy was delineated to develop and evaluate programs with a maximum chance of taming the obesity epidemic.

Adolescent↗