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PubMed1992

Practical guidelines for DNA-based testing in multiple endocrine neoplasia type 1.

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominant predisposition to neoplastic lesions of the parathyroid glands, the neuroendocrine pancreas, and the anterior pituitary gland. The predisposing genetic defect was localized to the long arm of chromosome 11 by genetic linkage analysis in three affected families. By analyzing six MEN 1 families with 14 DNA marker systems located close to the MEN 1 gene, we have developed a method to identify carriers of the MEN 1 predisposition. We describe practical aspects of such DNA-based diagnostic procedures.

Blotting, Southern↗
PubMed1960

Simultaneous multiple tuberculin testing.

In experimental work with tuberculin testing-for example, for comparing different testing procedures, for standardizing tuberculin, etc.-two tests are often given to each person. Because of variations in allergy from person to person, such duplicate testing gives a much more precise comparison of two test procedures for a given number of persons than does the alternate use from person to person of two test procedures to be compared. In adopting this method of testing it is tacitly assumed that the two tests in the same person do not interact in any way. The present paper shows, however, that this assumption is not justifiable.The authors describe an experiment in which 611 infants who had been BCG-vaccinated at 2-5 days of age were tuberculin-tested 3-5 months later, 306 of them with a single 10 TU test and 305 with a 10 TU test in one arm and a 100 TU test in the other arm. The results showed that there was a highly significant difference between the two groups, both in the average size of the reactions and in the degree of induration, the single-test group giving the larger and stronger 10 TU reactions.

Biomedical Research↗
PubMed2001

Premorbid IQ estimates from a multiple aptitude test battery: regression vs. equating.

Estimation of premorbid abilities remains an integral part of neuropsychological evaluations. Several methods of indirect estimation have been suggested in the literature. Many of these methods are based in prediction via linear regression. Unfortunately, linear regression has the well-reported tendency to underpredict high IQ scores and overpredict low IQ scores. This can be shown to be an unavoidable statistical artifact of linear regression. We demonstrate a procedure to estimate premorbid IQ without the regression artifact. The procedure has two steps: confirmation of construct equivalence and psychometric equating. An example using real data is presented which shows the regression to the mean problem with prediction and compares it to the results from equating.

Journal Article↗
PubMed2006

International Staging System required standardization of biochemical laboratory testing in multiple myeloma.

The standardization of biochemical measurement procedures in multiple myeloma is necessary for reliable prognostic stratification of patients in multicentric trials. The new prognostic index International Staging System for multiple myeloma uses only two laboratory markers, albumin and beta-2 microglobulin. Our study compared results of albumin, beta-2 microglobulin and monoclonal immunoglobulin measurements from six centers which provide treatment for multiple myeloma in the Czech Republic and attempted to standardize the analytic procedures. We have found that the measurement of albumin is well standardized and the results from all laboratories were comparable. The measurement of beta-2 microglobulin achieved comparability only after a partial unification of analytical methods. The determination of monoclonal immunoglobulin concentration provided comparable results for concentrations higher than 20 g/l with higher variability for lower values.

Antibodies, Monoclonal↗
PubMed1991

The misuse of predictive value--or why you must consider the odds.

The predictive value of a test is often misinterpreted because it is presented as a percent. It is intuitive to assume that low percentages (70% or less) are "bad" and high percentages are "good". A positive predictive value of 20%, for example, was cited as proof that a test should not be used even though the positive likelihood ratio for that same test was 50. A likelihood ratio of 50 means that the post test odds of disease for a positive test result will be 50 times higher than the pretest odds of disease. Now, that is a large increase in the odds. Critics of laboratory medicine fail to recognize that sensitivity and specificity vary with the strength of the signal. Thus, a value well above the cutoff is far more likely to indicate disease than does a value just above the cutoff--even though both are reported as "positive". Tables of likelihood ratios for a wide range of specific test results, or for multiple test results, provide more information than a simple four-by-four predictive value table. Likelihood ratios are also more informative than predictive values or ROC curves. Finally, critics of laboratory medicine fail to take into account the information to be derived from a confirmatory test, a repeat test at a later time, and from other tests.

Clinical Laboratory Techniques↗
PubMed1991

Multiple swallow test for the quantitative and qualitative evaluation of esophageal motility disorders.

Esophageal motility was evaluated from the analysis of six consecutive swallows. A sum image was generated comprising the representative information of an entire study. Calculation of emptying rates and characterization of the bolus behavior was performed from the sum image and the single swallow data. In 86 patients investigated, liquid and solid-phase studies showed a remarkable variation of single swallow data in normals (relative variation coefficient for liquid: 10%, solid: 14%), which were even higher (p less than 0.001) in patients with disorders (liquid: 31%, solid: 25%). As sum images compensate for this intra-individual variation, false-positive (liquid: 16%, solid: 25%) or negative single swallow findings (liquid: 36%, solid: 27%) are reduced. Qualitative analysis of condensed sum images provided characteristic image patterns representing different pathophysiologic aspects. Since the method introduced better discriminates between normal and pathologic function, it may enhance diagnostic accuracy.

Deglutition↗