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Results for “Predictive testing”

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PubMed1990

Highly specific prediction of antineoplastic drug resistance with an in vitro assay using suprapharmacologic drug exposures.

Bayes' theorem has been used to describe the relationship between the accuracy of a predictive test (posttest probability) and the overall incidence of what is being tested (pretest probability). Bayes' theorem indicates that laboratory assays will be accurate in the prediction of clinical drug resistance in tumors with high overall response rates (e.g., previously untreated breast cancer) only when the assays are extremely (greater than 98%) specific for drug resistance. We developed a highly specific drug-resistance assay in which human tumor colonies were cultured in soft agar and drugs were tested at high concentrations for long exposure times. Coefficients for concentration x time exceeded those reported in contemporaneous studies by about 100-fold. We reviewed 450 correlations between assay results and clinical response over an 8-year period. Results were analyzed by subsets, including different tumor histologies, single agents, and drug combinations. Extreme drug resistance (an assay result greater than or equal to SD below the median) was identified with greater than 99% specificity. Only one of 127 patients with tumors showing extreme drug resistance responded to chemotherapy. This negligible posttest probability of response was independent of pretest (expected) probability of response. Once this population of patients with tumors showing extreme drug resistance had been identified, posttest response probabilities for the remaining cohorts of patients varied according to both assay results and pretest response probabilities, precisely according to predictions based on Bayes' theorem. This finding allowed the construction of a nomogram for determining assay-predicted probability of response.

Antineoplastic Agents↗
PubMedDate not supplied

On neural network techniques in the secure management of communication systems through improving and quality assessing pseudorandom stream generators.

Random components play an especially important role in the management of secure communication systems, with emphasis on the key management of cryptographic protocols. For this reason, the existence of strong pseudo random number generators is highly required. This paper presents novel techniques, which rely on Artificial Neural Network (ANN) architectures, to strengthen traditional generators such as IDEA and ANSI X.9 based on 3DES and IDEA. Additionally, this paper proposes a non-linear test method for the quality assessment of the required non-predictability property, which relies on feedforward neural networks. This non-predictability test method along with commonly used empirical tests based on statistics is proposed as a methodology for quality assessing strong pseudorandom stream generators. By means of this methodology, traditional and Neural Network based pseudorandom stream generators are evaluated. The results show that the proposed generators behave significantly better than the traditional ones, in particular, in terms of non-predictability.

Computer Communication Networks↗
PubMed1996

Ethanol resistive microbubble test: a modification of the stable microbubble test used to predict respiratory distress syndrome.

The stable microbubble (SM) test on gastric aspirate obtained at birth proved useful in identifying infants who would develop respiratory distress syndrome (RDS). This test involves only the count of stable microbubbles of < or = 15 microns in diameter. Larger bubbles (> 15 microns in diameter) are not necessary for the test and may interfere with stable microbubble counting. The aims of the present study were to determine: (i) if larger bubbles could be selectively removed by adding ethanol, a potent bubble breaker; and (ii) if the predictive value of this modified test, the ethanol resistive microbubble (ERM) test, on the development of RDS was similar to that of the SM test. Varying amounts of different concentrations of ethanol-water solutions were added to the top of the bubble crop generated by the SM test procedure, and the mean counts of stable microbubbles and larger bubbles in five regions were calculated. A volume of 10 microL of 47.5% ethanol was effective in defoaming larger bubbles generated by the SM test procedure without altering the stable microbubble counts. When concurrently performed on 43 samples of gastric aspirate obtained at birth from infants of less than 35 weeks gestation, the RDS predictive value of the ERM test was similar to that of the SM test. It was concluded that the ERM test may serve as an alternative to the SM test.

Amniotic Fluid↗
PubMed2003

Predicting difficult orotracheal intubation in pharyngo-laryngeal disease: preliminary results of a composite index.

PURPOSE: Prediction of difficulty in orotracheal intubation (DI) in patients undergoing laryngeal microsurgery should help reduce the morbidity-mortality associated with this clinical situation. To establish a simple score to predict this difficulty, we studied 11 variables and their association with DI in these patients. METHODS: The study included 181 patients. The variables evaluated were: Mallampati grade, thyromental distance, mouth opening, temporomandibular joint movement, tooth morphology, maxillary deficiency, head and neck movement, receding mandible, body mass index, and clinical symptoms of laryngeal and supraglottic disease. To establish the score, regression coefficients of the statistically significant variables were used on adjusted logistic regression analysis. RESULTS: DI was present in 50 patients (28%) and orotracheal intubation was impossible in four (2%). Except for obesity, all the variables evaluated were predictive of DI. A simple predictive test was established based on logistic regression analysis including all the variables except temporomandibular joint movement. To determine the optimum cut-off for the new test, a receiver operating characteristic curve analysis was applied. A score > or = 5 in the proposed test provided a sensitivity of 94% and a specificity of 76%. CONCLUSION: The index we describe is aimed at predicting DI in a very specific population with a high risk of this complication. This index uses a series of variables which may be measured easily during the preoperative period and provides an excellent predictive capacity with a high sensitivity and specificity when the index is > or = 5.

Female↗
PubMed1988

Perception testing in surgical pathology.

A test predictive of mature pathologic expertise could be of great value in the selection of individuals entering the field. Some individuals may have an aptitude superior to others to discriminate images based on the discovery of distinctive image features. This may enhance their ability to draw pathologic conclusions from clinical images and may favorably affect their performance as pathologists. A form of the Facial Recognition Test was administered to pathology residents and faculty to test this hypothesis. Facial recognition results correlated well with resident performance measured by overall faculty ratings, but only marginally with performance measured by scores on "direct recognition" slides of the American Society of Clinical Pathologists' in-service pathology exams. These preliminary results indicate that testing of visual discrimination may be predictive of resident performance in pathology. A test of this type could eventually be useful in selection and self selection of resident candidates and in development of remedial training for residents experiencing difficulty in learning morphologic interpretation.

Humans↗
PubMed2003

Dual nonlinearities regulate contrast sensitivity in pattern discrimination tasks.

Many current psychophysical models propose that visual processing in cortex is hierarchical, with nonlinearities sandwiched between linear stages of processing. In earlier publications, we proposed a model of this type to account for masking effects found with spatial frequency and orientation discriminations. Our model includes two nonlinear mechanisms that regulate contrast sensitivity in early cortical mechanisms. The first is a local within-pathway nonlinearity that accelerates at low contrasts but is compressive at high. The second is a pooled nonlinear gain control process that operates over a broad range of neurons with different tuning characteristics. Here, we test predictions of the model for spatial frequency discriminations. The model predicts that at low contrasts, adding a grating mask oriented parallel to test gratings will improve discrimination performance via operation of the within-pathway nonlinearity, analogous to the "dipper effect" found with contrast discriminations. Adding an orthogonally oriented mask is predicted to have no effect at low contrasts, where pooled gain control processes contribute little to performance. At high contrasts, the model predicts that performance will asymptote and become independent of contrast with either parallel or orthogonal masks. The results confirm model predictions.

Adult↗
PubMed1998

An evaluation of common breast cancer gene mutations in a population of Ashkenazi Jews.

OBJECTIVES: In view of the recent reports of recurrent mutations in BRCA1 and BRCA2 in the Ashkenazi Jewish population, we have undertaken to assess the frequency of these mutations in this population attending for genetic counselling and risk assessment of familial breast cancer. DESIGN: Mutation screening for the 185delAG and the 5382insC mutations in BRCA1 and the 6174delT mutation in BRCA2 was performed on DNA samples from either subjects affected by breast or ovarian cancer or obligate gene carriers. The likelihood of the cancers being hereditary in each family was calculated. SUBJECTS: Blood samples were obtained from 26 affected subjects or obligate gene carriers from 23 Ashkenazi Jewish families, all with a history of either early onset breast or ovarian cancers, or multiple cases of breast or ovarian cancer. RESULTS: Twelve mutations have been identified in the 23 families (52%) of which eight (67%) were the 185delAG mutation, three (25%) were the 6174delT mutation, and one (8%) was the 5382insC mutation. While the majority of these mutations were identified in families with a greater than 50% probability of being hereditary under the CASH segregation model, three mutations were identified in families with a 35% or less probability. CONCLUSIONS: Genetic screening of the recurrent mutations in Ashkenazi Jewish families will lead to the availability of predictive testing in a reasonably large proportion, even if the family history of breast/ovarian cancer is not particularly strong. In our view it is possible to reassure high risk unaffected members of these families, if the screening is negative for these mutations, even if a sample from an affected member of the family is unavailable for previous screening.

Adult↗
PubMed1991

Presymptomatic screening for multiple endocrine neoplasia type 2A with linked DNA markers. The MEN 2A International Collaborative Group.

Seven DNA markers from the pericentromeric region of chromosome 10 were tested for linkage to MEN 2A in a panel of 17 families. Four of the markers proved to be tightly linked and therefore suitable for predictive testing. The markers were used to estimate carrier risks for individuals who had a negative biochemical screening test for thyroid C-cell hyperplasia. The analysis substantially altered the carrier risks of most of these individuals, which suggests that typing with DNA markers should be introduced into the screening programme of MEN 2A families. Accurate prenatal diagnosis for this disorder is also now possible.

Adult↗
PubMed1984

Amniotic fluid analysis in prenatal diagnosis of neural tube defects: a comparison between six biochemical tests supplementary to the measurement of amniotic fluid alpha-fetoprotein.

Concanavalin A (con A) and lens culinaris agglutinin (LCA) microheterogeneity pattern of AFP (crossed affinity immunoelectrophoresis), alpha-2-macroglobulin and synaptic membrane protein D-2 (rocket immunoelectrophoresis) and qualitative (polyacrylamide gel electrophoresis) and quantitative (enzyme kinetic reaction rate) acetylcholinesterase were analysed in 87 consequtive samples from normal pregnancies and 37 abnormal samples (fetal neural tube defect or abdominal wall defect). Very few false positive results were obtained in normal pregnancies with any of the tests. In all cases of neural tube defects the correct result was obtained with qualitative acetylcholinesterase analysis, whereas only 2/3 of the abdominal wall defects were correctly predicted. Testing with con A or LCA was less optimal in neural tube defects, whereas all abdominal wall defects could be predicted correctly. Acetylcholinesterase in the quantitative test and protein D-2 did not decrease the rate of false results. Determination of the alpha-2-macroglobulin concentration performed well in the present study, but is not recommended because of the very high susceptibility to contamination of amniotic fluid with fetal or maternal blood.

Abdominal Muscles↗
PubMed1993

Seroquel: behavioral effects in conventional and novel tests for atypical antipsychotic drug.

Seroquel was compared to clozapine and several other antipsychotic agents in tests predictive of antipsychotic activity or extrapyramidal symptoms. In the conditioned avoidance test in squirrel monkeys as well as several paradigms using apomorphine or amphetamine-induced behavioral alterations, seroquel displayed the profile of a drug with potential antipsychotic activity. In these paradigms the potency of seroquel was somewhat less than clozapine in rodent tests, while the reverse was true in higher species, i.e. monkeys, cats. In tests designed to evaluate the propensity to induce EPS or tardive dyskinesia, for example, the production of dyskinetic reactions in haloperidol-sensitized cebus monkeys, seroquel displayed a profile similar to clozapine and disparate from typical antipsychotic drugs. In drug-naive cebus monkeys seroquel sensitized significantly fewer monkeys than haloperidol and the dyskinetic reactions were of significantly less intensity. It is anticipated that this novel antipsychotic agent will have a significantly reduced propensity to produce extrapyramidal symptoms and tardive dyskinesia than typical antipsychotics.

Amphetamine↗
PubMed1988

Chronic pain and depression: toward a cognitive-behavioral mediation model.

Although considerable attention has recently been devoted to explaining why depression is a frequent concomitant of chronic pain, little empirical work has been conducted to test predictions based on these models. The present study was designed to test a cognitive-behavioral mediation model of pain and depression that proposes perceived reduction in instrumental activities along with a decline in perceptions of control and personal mastery are necessary prerequisites for the development of depressive symptomatology in pain patients. According to this model, in contrast to alternative models, the presence of pain is not sufficient condition for the subsequent development of depression. This model was tested and confirmed through the application of structural modeling with latent variables. Specifically, the direct link between pain and depression was found to be non-significant, however, measures of perceived life interference and self-control were found to be significant intervening variables between pain and depression. These results provide the first empirical demonstration that psychological mediators may be involved in the development of depression secondary to chronic pain. The findings of this study are contrasted with single-factor models that postulate both chronic pain and depression as resulting from a common cause.

Adult↗
PubMed2002

Non-linear EEG measures during sleep: effects of the different sleep stages and cyclic alternating pattern.

The objective of this work was to study the non-linear aspects of sleep EEG, taking into account the different sleep stages and the peculiar organization of its phasic events in ordered sequences (CAP) by applying a series of new non-linear measures (non-linear cross prediction or NLCP), which appear more reliable for the detection and characterization of non-linear structures in experimental data than the commonly used correlation dimension. Eight healthy subjects aged 18-20 years participated in this study. Polysomnography was performed in all subjects; signals were sampled at 128 Hz and stored on hard disk. The C3 or C4 derivation was used for all the subsequent computational steps, which were performed on EEG epochs (4096 data points) selected from sleep stage 2 (S2) and slow-wave sleep (SWS), in both CAP and non-CAP (NCAP) conditions. Also, epochs from sleep stage 1 (S1), REM and wakefulness preceding sleep were recorded. The dynamic properties of the EEG were assessed by means of the non-linear cross-prediction test, which uses three different 'model' time series in order to predict non-linearly the original data set (Pred, Ama, and Tir). Pred is a measure of the predictability of the time series, and Ama and Tir are measures of asymmetry, indicating non-linear structure. The non-linear measures applied in this study indicate that sleep EEG tends to show non-linear structure only during CAP periods, both during S2 and SWS. Moreover, during CAP periods, non-linearity can only be detected during the phase A1 subtypes (and partially A2) of CAP. The A3 phases show characteristics of non-stationarity and bear some resemblance to wakefulness. Based on the results of this study, sleep might be considered as a dynamically evolving sequence of different states of the EEG, which we could track by detecting non-linearity, mostly in association with CAP. Our results clearly show that detectable non-linearity in the EEG is closely related to the occurrence of the phase A of CAP.

Adolescent↗
PubMed2003

Nonlinear EEG analysis during sleep in premature and full-term newborns.

OBJECTIVE: Recently it has been shown that the adult sleep EEG is mostly determined by high-dimensional, linear dynamics with the exception of the A phase of the cyclic alternating pattern which displays more synchronized nonlinear dynamics. It is not known how these two different types of brain dynamics develop in early life; for this reason the aim of this study was that to extend the nonlinear analysis to the EEG during sleep recorded in premature and full-term newborns. METHODS: EEG epochs were chosen from a total of 24 polygraphic recordings from 14 babies (9 males and 5 females) aged between 33 weeks 3 days and 4 months conceptional age. All subjects were neurologically normal and showed normal psychomotor development at follow-up. A total of 243 artifact-free epochs was chosen during active sleep (AS, 74 total epochs), quiet sleep (QS, 76 total epochs) and indeterminate sleep (IS, 93 total epochs). The dynamic properties of the EEG were assessed by means of the nonlinear cross prediction test which uses 3 different 'model' time series in order to predict nonlinearly the original data set (Pred, Ama, and Tir). Pred is a measure of the predictability of the time series, and Ama and Tir are measures of asymmetry, indicating nonlinear structure. RESULTS: Our results show that the structure of sleep EEG in newborns is significantly different from that of adults, it cannot be distinguished from that of high-dimensional noise in the majority of epochs, and shows a tendency to become nonlinear in nature, mostly during QS, in a small percentage of the epochs analyzed. CONCLUSIONS: These findings can be interpreted as the effect of immature synaptic interconnections between neurons in the newborn brain.

Aging↗
PubMed2004

The Informant Questionnaire on cognitive decline in the elderly (IQCODE): a review.

BACKGROUND AND AIMS: The IQCODE is widely used as a screening test for dementia, particularly where the subject is unable to undergo direct cognitive testing or for screening in populations with low levels of education and literacy. This review draws together research on the psychometric properties and validity of the IQCODE. METHOD: A systematic search of the literature was carried out using three databases. RESULTS: The review shows that the questionnaire has high reliability and measures a single general factor of cognitive decline. It validly reflects past cognitive decline, performs at least as well at screening as conventional cognitive screening tests, predicts incident dementia, and correlates with a wide range of cognitive tests. A particular strength is that the IQCODE is relatively unaffected by education and pre-morbid ability or by proficiency in the culture's dominant language. The disadvantage of the IQCODE is that it is affected by informant characteristics such as depression and anxiety in the informant and the quality of the relationship between the informant and the subject. CONCLUSIONS: Because the IQCODE provides information complementary to brief cognitive tests, harnessing them together can improve screening accuracy.

Aged↗
PubMed1982

Genotoxic activity of five antidepressant hydrazines in a battery of in vivo and in vitro short-term tests.

Five antidepressant agents (monoamine oxidase inhibitors) having a hydrazino group--phenelzine, nialamide, mebanazine, isocarboxazid, and iproniazid--were assayed in four in vivo or in vitro short-term tests predictive of the potential carcinogenicity of chemicals. (1) All the compounds tested except iproniazid, produced DNA fragmentation, as evaluated by the alkaline elution technique, in liver and/or lung cells of mice treated ip or po. (2) All the compounds except mebanazine (which was no longer available for testing) were weak inducers of sister chromatid exchanges in bone marrow cells of mice treated ip. (3) Phenelzine and nialamide elicited base-pair substitutions and mebanazine elicited frameshift errors in his- Salmonella typhimurium. S9 mix containing rat liver, mouse liver, or mouse lung S9 fractions had variable effects on mutagenicity. (4) The same three compounds were positive in a DNA repair bacterial test with five trp- Escherichia coli strains lacking a variety of repair mechanisms (uvrA, polA, recA, lexA) or incorporating plasmids (R391).

Animals↗
PubMed2004

Oxidative stress and preeclampsia: rationale for antioxidant clinical trials.

Preeclampsia remains a frequent and potentially dangerous complication of pregnancy. The cause remains largely unknown, but oxidative stress and a generalized inflammatory state are features of the maternal syndrome. The placenta appears to be the principal source of free radical synthesis but maternal leukocytes and the maternal endothelium are also likely contributors. Recent reports have suggested an important role for placental trophoblast NAD(P)H oxidase in free radical generation in preeclampsia. The antioxidant vitamin E is now known to have multiple actions in addition to prevention of lipid peroxidation (ie, inhibition of NAD(P)H oxidase activation and the inflammatory response). In view of the abnormally low plasma vitamin C concentrations in preeclampsia, a combination of vitamins C and E is a promising prophylactic strategy for prevention of preeclampsia. Several multicenter randomized clinical trials are now underway. The potential use of antioxidants and the recognized, albeit modest, benefit of low-dose aspirin prophylaxis have heightened the need for a reliable predictive test for preeclampsia. A combination test involving several relevant biomarkers is likely to provide the best predictive potential.

Antioxidants↗
PubMed2005

Hereditary ataxia and behavior.

Recognizing cognitive deficits and psychiatric disorders in patients with autosomal dominant ataxias is relatively new. At this time, the percentage of patients with these disorders who experience changes in cognition or psychiatric symptoms is unknown. Cognitive impairment, when seen, is often found on tests of executive function, probably reflecting disruption of afferent and efferent pathways of the prefrontal cortex and subcortical structures, including the cerebellum. Widespread global dysfunction does occur in some cases, especially later in the disease course. Psychiatric symptoms including depression, aggression, irritability, and psychosis have all been reported. As these behavioral changes receive further study, one hopes that guidelines for treating these symptoms will emerge. Clinicians should be mindful of the psychosocial effects that genetic testing for the hereditary ataxias may have, especially in cases of predictive testing for those who are asymptomatic but at risk because of family history. Guidelines established for genetic testing in HD may be helpful when approaching these cases.

Behavior↗
PubMed1995

Skin irritation testing in man for hazard assessment--evaluation of four patch systems.

1. The limitations of the Draize rabbit skin irritation test for hazard evaluation for man are widely documented. Nevertheless it remains the prescribed method for determining acute skin irritations hazard. 2. While the use of human testing for risk assessment of irritants is well established, the use of predictive testing in man for hazard identification has not been explored widely, and this is the object of the research programme. 3. The experiment described in this report evaluates the sensitivity of four patch testing systems (Finn chamber, Hill Top patch, Van der Bend chamber, and Webril patch) using a total of six irritant substances. 4. Following preliminary range-finding experiments, test materials were applied to the upper outer arm for up to 4 h. Assessments were performed immediately after patch removal and at 1, 24, 48, and 72 h. 5. Webril and Hill Top patches generated the greatest levels of response, although responses with Finn and Van der Bend were observed. Hill Top patches are recommended for future development work. 6. The use of very small preliminary panels to predict the effects in larger panels using different volunteers was only of limited value as each volunteer was found to have different irritant thresholds.

Acetates↗