Showing papers on "False positive paradox published in 1975"

Method for differentiation of nonspecific from specfic toxoplasma IgM fluorescent antibodies in patients with rheumatoid factor.

Abstract: In a study performed to define the prevalence of false positive toxoplasma IgM-IFA test results in sera containing RF, 8 (19.5%) of 41 sera which were positive for RF were positive in the toxoplasma DT and conventional toxoplasma IFA test. Three of these eight were also positive in the toxoplasma IgM-IFA test and in two, the results were considered to be false positives. Of the 33 sera remaining which were positive for RF but negative in both the DT and conventional IFA test, three were positive in the toxoplasma IgM-IFA test. Of 51 sera from patients with suspected rheumatoid arthritis or other collagen vascular disorders, all of which were negative when tested for RF, none was positive for toxoplasma IgM antibodies in the IgM-IFA test. Sera from 15 adults with the acute lymphadenopathic form of toxoplasmosis and 13 infants with congenital toxoplasmosis were tested for the presence of RF. Whereas none of the sera from the acquired cases had demonstrable RF, two of the congenital cases had RF, and their titers were both 1:320. False positive IgM-IFA test results became negative after treatment of sera with heat-aggregated IgG. In contrast, IgM-IFA test titers in cases of acute congenital or acquired toxoplasmosis were unaffected by this treatment. Thus, treatment with heat-aggregated IgG can be used to differentiate false positive IgM-IFA test titers due to RF from those due to specific IgM toxoplasma antibody.

The patch test--who should and should not use it and why.

Abstract: Since its introduction into medicine by Joseph Jadassohn in 1895, the patch test has proven its supreme value in tens of thousands of cases and in research. But emphasis must be placed on the grave errors which can occur when the test is used improperly. Errors are common in the direction of both false positives and false negatives. Common causes of errors are described in detail. The conclusion is drawn that this valuable test had best be used only by those who have been adequately trained and who can apply it regularly on a sufficiently large number of selected patients.

The prediction of glaucoma from ocular biometric data. Part 2. An evaluation.

Abstract: A method of glaucoma prediction from ocular biometric data has been described previously. A study was undertaken to evaluate the performance of the existing multiple regression equations (prediction systems) on data obtained from an independent sample consisting of 22 angle-closure glaucoma, 29 open angle glaucoma and 44 normal subjects. This performance, found by comparing the predicted and actual classification for this sample, was such that between 2 and 7% false positives and 12 and 27% false negatives were found on the equations differentiating glaucoma from normal subjects; and between 14 and 27% false positives, with 10 to 14% false negatives on the equations classifying the glaucoma subjects as angle-closure or open angle. From these results the efficiency of glaucoma prediction from ocular biometric data would appear to be equal to that of the combined tonography and provocative tests, provocation with corticosteroids and visual field screening.

Thermography in diagnosis of breast diseases.

Abstract: While carrying out 10,000 breast thermographic studies we have examined 4,000 palpable lesions, 1,100 of which were verified cancers. The study of these cases according to our classification into 5 categories has shown that: (1) in the benign lesions, there were 18% equivocal results and 13% 'false positives', and (2) in the malignant diseases, there were 18% doubtful thermograms, 8.5% 'false negatives' and 10% 'false positives'. Thermography allowed us to detect 10 subclinical and 56 occult cancers; in another connection we have identified a growth phase in 11% of our cancers (fast-growth forms).

The College of American Pathologists comprehensive blood bank survey program, 1973.

Abstract: The 1973 Comprehensive Blood Bank Survey Program of the College of American Pathologists was administered to 2,200 laboratories and blood banks throughout the United States. The results showed a considerable increase in the accuracy of the testing and in the performance of reagents. Accuracy of ABO testing was 99.3%; Rh testing, 99%; crossmatching was 98.9% correct. Antibody detection was correct 96.3% of the time, with the exception of a cold-reacting anti-P1 which was found by only 62% of the participants. About the same number of laboratories also did not find the antibody during the crossmatch procedure. A sample from a donor with a positive antiglobulin test created much confusion and was misinterpreted in a number of ways. Reagents were found to be performing well with the exception of two, one [anti-hr'(C)] which produced a significant number of false positives, and another (anti-Kell) which produced numerous false negatives. The results seem to indicate that the anti-hr'(C) from several manufacturers is at fault for this error, while the anti-Kell errors showed no predilection for manufacturers and may represent erroneous testing by the laboratories or a failure to employ adequate quality control.

The prediction of glaucoma from ocular biometric data. Part 1. An application of multiple regression analysis.

Abstract: Two sets of multiple regression equations (prediction systems) were derived from the analysis of ocular biometric data obtained from glaucoma patients (16 open angle; 16 angle-closure) and 75 normal subjects. Discriminant scores were established for both sets of equations which minimised the number of false negatives. One set, the 'Glaucoma Equations' was applied to the data to segregate the glaucoma from the normal subjects. The other prediction system, the 'Classification Equations,' was then applied to the group defined as glaucomatous to discriminate between patients in the angle-closure and open angle categories. The performance of these equations, obtained by comparing the predicted and actual classifications for this sample, was such that between 9 and 12% of false positives and 0 and 3% false negatives were found on the 'Glaucoma Equations' and between 6 and 12% of false positives with no false negatives on the 'Classification Equations.'

[Observer error in interpretation of chest-radiophotographs (author's transl)].

Abstract: A series of 434 radiophotographs (70 X 70 mm) containing 40 patients with known abnormal symptoms and 15 resp. 21 pictures with suspected abnormalities were interpreted by 85 chest physicians. 84% (average of 77 readers) of the known symptoms were found in the right localisation. The mean value of 8 diagnosticians with only little routine in reading radiophotographs, was 65%. The number of correct findings with respect of the 40 plus 15 resp. 21 abnormalities lies near 80%. Nearly 10% of the true negative cases were described as positive by the diagnosticians. The number of false positives varies considerably (between 0% and 50%) for different interpreters. The number of true positive findings when the films are read by two observers independently increases only when we combine two readers with poor results in finding true positive cases. But dual reading means nearly twice as much false positive findings. The repetition of reading the films by the same interpreter gives nearly the same results as the first reading.