Showing papers on "False positive paradox published in 1988"

False positive rates in the determination of changes in probing depth-related periodontal measurements.

Abstract: False positive rates associated with changes in periodontal probing measurements (changes which are of such magnitude as to be construed as due to disease or healing when the observed changes are actually due to measurement error) were estimated by computerized simulation. In the first phase of the simulation study, various distributions of error variances among sites were evaluated for their ability to produce matches to an empirical distribution of differences between replicate measurements. In the second phase of the study, distributions of variances identified in Phase I were used to estimate the false positive rate, under conditions of no actual change, for detection methods based on critical differences between averaged pairs of measurements. This rate was found to be substantially greater than that predicted using normal distribution probabilities and, for a difference of ≥2.5 mm, approached one false detection per examination of 168 sites. In the third phase of the study, simulation procedures were extended to the tolerance detection methodology and the false positive rate, in the absence of real change, was almost one detection per two examinations. This simulation suggested that perhaps one third of tolerance detected “bursts” of periodontal attachment change may be false positives attributable to measurement error.

EEG outside the hairline: detection of epileptiform abnormalities.

Abstract: We have assessed the reliability in 25 epileptic patients of EEG recording using disposable self-adhesive electrodes and a seven-channel extra-hairline montage, through comparison to simultaneous standard cable telemetry. Epileptiform abnormalities were detected in all patients on blind interpretation of data acquired using the novel technique. On comparison of specific epileptiform abnormalities identified blindly, a false positive rate of 10% and a false negative rate of 8% were encountered. Posterior temporal complexes accounted for most false negatives, and most false positives did not represent failings of the recording technique. We conclude that EEG recording outside the hairline with disposable electrodes represents a reliable means to acquire, quickly and simply, EEG evidence of epilepsy. As such, it may prove useful in the acute evaluation of patients presenting with apparent seizures.

A new test for screening color vision: concurrent validity and utility.

Abstract: Recognizing the need for an effective test for screening color vision in young children, we have developed a new pseudoisochromatic (PIC) plate test which is useful for a wide variety of observers at different ages. The test consists of four plates and responses can be used to categorize color vision as normal or as either red-green or blue-yellow defective. Results of this validation study with adults, both color normal and red-green defective, show a high degree of correlation between the new test and the Nagel anomaloscope: there were no false positives and only a few false negatives, which occurred with mild deuteranomalous observers. The validity of the test compares favorably to the Ishihara, F-2, and the AO-HRR screening plates. Results with toddlers (3 to 6 years) indicate that the task demands of the test are well suited for testing young children. The percentage of color defectives identified in the toddler sample using the new test is closer to the adult prevalence than results obtained with the F-2 and AO-HRR screening plates, which gave dramatically higher failure rates. The new test is culture-free and can be administered rapidly to both verbal and nonverbal observers using pointing or preferential looking.

Diagnostic schemes for fine needle aspirates of breast masses.

Abstract: A comparison was made of four statistically based schemes for classifying epithelial cells from 243 fine needle aspirates of breast masses as benign or malignant. Two schemes were computer-generated decision trees and two were user generated. Eleven cytologic characteristics described in the literature as being useful in distinguishing benign from malignant breast aspirates were assessed on a scale of 1 to 10, with 1 being closest to that described as benign and 10 to that described as malignant. The original computer-generated dichotomous decision tree gave 6 false negatives and 12 false positives on the data set; another tree generated from the current data improved performance slightly, with 5 false negatives and 10 false positives. Maximum diagnostic overlap occurred at the cut-point of the original dichotomous tree. The insertion of a third node evaluating additional parameters resulted in one false negative and seven false positives. This performance was matched by summing the scores of the eight characteristics that individually were most effective in separating benign from malignant. We conclude that, while statistically designed, computer-generated dichotomous decision trees identify a starting sequence for applying cytologic characteristics to distinguish between benign and malignant breast aspirates, modifications based on human expert knowledge may result in schemes that improve diagnostic performance.

Optimal inspection under semi-markovian deterioration: basic results

Abstract: This article develops a model for determining the optimal inspection schedule for a system which deteriorates according to a semi-Markov process that progresses through three states: good, defective, and bad. A binary test is used, and false positives may occur. A true positive results in an action that reduces the likelihood of entering the bad state, but at most one such corrective action can occur during the lifetime of the system. Costs are associated with each inspection, each false positive, the corrective action, and the entrance into the bad state. Dynamic programming is used to compute the minimum expected cost, which is a function of the age of the system. The optimal inspection schedule is readily derived from this value function. Computational examples are provided. This model is appropriate for medical screening or for a mission where there is only one spare part.

PLS assessment of the performance of short-term tests for carcinogens

Abstract: Partial least squares modelling in latent variables is applied to the analysis of short-term test genotoxicity data obtained by testing 42 chemicals, known carcinogens and non-carcinogens, in 35 different assay systems that are deemed to be potential indicators of carcinogencity. Results of a preliminary analysis of all data, and of a second analysis on a reduced data base, are presented. The latter analysis provided a model explaining 73% of variance, whereby no false negative or positive was predicted among 38 chemicals, in spite of qualitative predictions indicating five false positives and two false negatives. Only nine out of 35 assays appear to be relevant to the description of carcinogenicity/non-carcinogenicity of chemical substances.

Immunohistochemical Localization of Hepatitis B Surface Antigen and Hepatitis B Core Antigen in Tissue Sections: A Source of False Positive Staining

Abstract: The occurrence of apparent false positive immunoperoxidase staining for hepatitis B surface antigen (HBsAg) led to the evaluation of several commercial antisera for usefulness in the diagnosis of hepatitis B by immunohistochemistry. One commercial antibody to hepatitis B core antigen (HBcAg) was tested and found to give sensitive and specific staining, with only a few false negatives and no false positives. Of three antibodies to HBsAg, one gave good staining results that were consistent with serologic data; one had many false positive stains due to contaminating antibodies to plasma proteins; and one (a monoclonal antibody) had many false negatives, probably due to its restricted antigenic specificity. Diagnosticians should be aware of the problems with false positive and false negative immunohistochemical stains. False positives in particular can be a significant problem, causing frequent misdiagnosis of hepatitis B.

[Receiver operating curve, an aid in decision making. Principles and applications illustrated with some examples].

Abstract: The practitioner has many difficult questions to resolve when he has placed in front of him more and more diagnostic and screening tests. Which is, in a given situation, the best test, by which is meant useful, least costly and most acceptable by the patient? Having chosen the test, at what level is the result to be considered positive or negative? The authors, having explained the principles and having taken some examples out of the literature of gynaecology and obstetrics, present a technique that shows on a receiver operating characteristic curve sensitivity and specificity sharing as a function of the possible levels for making decisions according to the test. The curve inordinate shows the sensitivity of the test or the number of true positives and on the abscissa the complement of specificity or the rate of false positives ford each decision threshold of the test. A simple glance gives the practitioner a view of the characteristics of the test over the whole band that this test can use. Using these curves it is possible to adopt more elaborate techniques to select the best threshold and to compare different tests.

Improving the Integrity of Pharmaceutical Sterility Testing: A New Robotic Approach

Abstract: Concern over the occurence of false positives within the sterility testing process has been and will continue to be of grave concern to pharmaceutical manufacturers. To date, very few truly effective solutions to this problem have been offered, while the FDA becomes ever more stringent over false positive results and second phase testing.A new robotic system for sterility test applications is described, which completely isolates the actual test area from human operators, and thus reduces substantially any possibility for false positives. The configuration utilizes the USP-preferred membrane filtration method, and uses the Millipore Steritest filtration chambers as its “output” for incubation. The system allows a technician to simply place product to be tested in an input station, mount the Steritest cannisters in designated sockets, then remove the empty containers and filled cannisters post-processing and incubate. This new method allows for the testing of a variety of different sample containers...

Clinical Application of Brain-stem Audiometry

Abstract: Based on the examination of 249 consecutive patients, the usefulness of brain-stem response audiometry in a major audiological clinic was evaluated. Auditory brain-stem responses were performed either for hearing threshold determination (67 patients) or for assessment of retrocochlear hearing loss (182 patients). The results demonstrate that ABR is a reliable method for the estimation of hearing thresholds in non-cooperative subjects. The rate of false positives was 5% and no false negatives were found. In combination with caloric testing, ABR is considered a valuable testing procedure in the audiological clinic and it may form the basis for submission to brain imaging examination when a suspicion of retrocochlear hearing disorder is raised. Concerning the diagnosis of retrocochlear hearing disorder, no false negatives have yet been found, while a rate of 13% of false positives has been indicated.

New AIDS test is said to reduce false positives

Abstract: SmithKline Beckman has developed a new test for AIDS antibodies that it says will reduce or eliminate false positive tests and greatly reduce inconclusive results. According to Harry C. Groome III, president of SmithKline Bio-Science Laboratories (the company's network of clinical testing laboratories), SmithKline will use its new Hivagen test to replace the Western blot assay, the current standard confirmatory test for human immunodeficiency virus (HIV). Those blood samples tested by the company's laboratories that test positive on the enzyme-linked immunosorbent assay (ELISA) will be confirmed using the Hivagen test, he says. SmithKline will neither sell kits nor license its Hivagen test. Instead, Groome says, SmithKline will handle confirmatory test procedures for $80 per test at its facilities in Van Nuys, Calif. With 500,000 confirmatory tests performed last year, and more expected this year, the potential market for Hivagen is at least $40 million. Because the Hivagen test is a clinical testing proc...

A knowledge-based approach to the automated detection of EEG waveforms

Abstract: Reliable automated detection of EEG waveforms should involve adequate and efficient utilization of heuristics used in the visual EEG analysis process, which include spatiotemporal information. The knowledge-based approach to automated EEG waveform detection quantifies efficiently the highly qualitative reasoning used in visual EEG analysis and provides an effective means for dealing with the problem of misses and false positive detections. The knowledge-based system follows an object-oriented strategy with procedural information attached to frame-based descriptions. It is also implemented in KEE on a Symbolics 3640 LISP computer, and involves a blackboard scheme as well. The overall system has been tested with data from several subjects, and it shows good agreement with the electroencephalographer minimizing false positive detections due to sharp but normal EEG activity, or to sharp but artifactual (non-EEG) activity. >