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Median Absolute Deviation (median + absolute_deviation)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Determination of rank by median absolute deviation (DRMAD): a simple method for determining the number of principal factors responsible for a data matrix,

JOURNAL OF CHEMOMETRICS, Issue 1 2009
Edmund R. Malinowski
Abstract Median absolute deviation (MAD) is a well-established statistical method for determining outliers. This simple statistic can be used to determine the number of principal factors responsible for a data matrix by direct application to the residual standard deviation (RSD) obtained from principal component analysis (PCA). Unlike many other popular methods the proposed method, called determination of rank by MAD (DRMAD), does not involve the use of pseudo degrees of freedom, pseudo F -tests, extensive calibration tables, time-consuming iterations, nor empirical procedures. The method does not require strict adherence to normal distributions of experimental uncertainties. The computations are direct, simple to use and extremely fast, ideally suitable for online data processing. The results obtained using various sets of chemical data previously reported in the chemical literature agree with the early work. Limitations of the method, determined from model data, are discussed. An algorithm, written in MATLAB format, is presented in the Appendix. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Brain natriuretic peptide in the prediction of recurrence of angina pectoris

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2 2004
H. Takase
Abstract Background, Circulating levels of brain natriuretic peptide (BNP) provide prognostic information for patients with heart failure, but little is known about its prognostic usefulness in patients with stable angina pectoris. We investigated whether BNP could be used as a marker for the prediction of anginal recurrence after successful treatment. Design, Brain natriuretic peptide levels of 77 patients with stable angina pectoris were measured at enrolment and after confirmation of successful treatment (i.e. no anginal attack for at least 6 months: chronic phase) with percutaneous transluminal coronary angioplasty and/or conventional medication. Then, we prospectively followed them up for 25·9 ± 1·4 months, with the endpoint being a recurrence of anginal attacks. Results, An anginal attack recurred in seven patients. In patients without recurrence, BNP levels in the chronic phase (21 ± 12 [median ± median absolute deviation] pg mL,1) were lower than those measured at enrolment (46 ± 25 pg mL,1, P < 0·0001), whereas the levels in patients with recurrence increased during the same period (from 36 ± 16 to 72 ± 42 pg mL,1, P < 0·05). A univariate analysis revealed that the BNP level measured in the chronic phase was the significant predictor of future anginal recurrence. Analysis of the receiver operating characteristic curve indicated that the cutoff level of BNP in the chronic phase was 68 pg mL,1. The Kaplan-Meier method revealed that the incidence of anginal recurrence was higher in patients with higher (71·4%) than lower levels of BNP (2·9%; P < 0·0001). Conclusions, Measurement of BNP levels after successful therapy is clinically useful for the prediction of recurrence of anginal attacks in patients with angina pectoris. [source]

Determination of rank by median absolute deviation (DRMAD): a simple method for determining the number of principal factors responsible for a data matrix,

Threshold levels of purified natural Bos d 2 for inducing bronchial airway response in asthmatic patients

CLINICAL & EXPERIMENTAL ALLERGY, Issue 10 2002
T. Zeiler
Summary Background Provocation tests are invaluable in establishing threshold levels and a causal relationship between atopic asthma and a certain allergen source, especially in relation to work-associated exposure. Purified major allergens open possibilities for a more accurate assessment of sensitization. Objective To determine the threshold dose of purified major bovine dander allergen Bos d 2 in bronchial provocation in comparison with the standard allergen and a set of other parameters of allergy. Method Nine consecutive patients referred to hospital for confirming the bovine origin of their occupational asthma were subjected to bronchial provocation tests with purified natural Bos d 2 and a standard bovine dander allergen. Additional tests included bronchial histamine challenge, measurements of total IgE, specific IgE antibody determinations and skin prick tests (SPT) with both allergens. Results In the provocation tests with Bos d 2, a 15% decrease in the forced expiratory volume in 1 s (FEV1) and/or peak expiratory flow (PEF) values in eight out of nine patients confirmed the predominant role of Bos d 2 in the sensitization. The threshold dose of Bos d 2 varied from 0.1 µg to > 100 µg (median ± median absolute deviation = 4.5 ± 3.9 µg). A positive SPT was induced by a median dose of 13.9 ± 9.8 µg of Bos d 2. Bronchial response to histamine and IgE antibodies against Bos d 2 showed the highest correlations to the provocations results. Conclusions The efficacy of Bos d 2 in bronchial provocation in patients with occupational cattle-associated asthma was confirmed and the range of the threshold level was determined. There were individual variations, but the response in provocation remains the reference method for identification of the cause of occupational atopic asthma. SPT and the measurement of specific IgE antibodies, preferably with purified or recombinant major allergens, increase the accuracy of the diagnosis. [source]