Optimal Partitioning Method for Evaluating of Effect of Hemoglobin Oxygenation Levels of Vessel Endothelial Growth Factor

Abstract

The work is aimed to study relationship between vessel endothelial growth factor (VEGF) serum levels and hypoxia in patients with severe neurological disorders. Overviewed literature sources indicate activation of VEGF synthesis during hypoxia. But standard correlation analysis does not reveal a statistically significant association between VEGF levels and pulse oxymetry parameters objectively assessing oxygen supply. Due to a proposed in the paper technique it became possible to reveal valid relationship between VEGF levels and oxygenation. This relationship can be described as increase of correlation between VEGF and immunological complement C4 when oxygenation level is below a certain threshold. Developed method includes searching of such boundaries for oxymetry parameters that correlation coefficients between VEGF and some additional factor Z in formed group are maximally different. ranges. The original technique based on permutation test was used not only to asses validity of effects associated with each oxymetry parameter but also to evaluate joint effect by full group of such factors. Great number of variable from database were tested as additional factors. So additional correction of validity was made to take into account multiple testing.

Determining Subgroups of Significant Correlation in Analyzing Relation between NR2 Antibodies and Factor VIII in Acute Neurological Diseases

“…This approach to assessing statistical significance is consistent with the concept of fully significant regularities discussed earlier in the works [1,2,3]. Ignoring the requirement to achieve full significance can lead to an erroneous conclusion about the existence of combined effects on data configurations arising from of simpler effects [1].…”

“…In the works [2,3] the boundary b was selected so that the special quality functional Q, which characterizes the presence of a high degree of correlation between the variables X and Y on one side of the boundary and at the same time the difference between the correlation coefficients to the left and right of the border reached the maximum possible value. The following functional was used:…”

“…The purpose of this work is, among other things, to prove the existence of a pronounced correlation between ABNR2 and FVIII in a group of patients, which can be distinguished by the values of the third factor, which in our case is VEGF. The use of the VCLR variant of the method of optimal valid partitions [2,3] to assess the significance of such a combined effect did not allow us to assess the significance of the combined effect at a sufficient level. The analysis of the shortcomings of this option, carried out in the next section, allowed us to develop a new modification of the VCLR method, which makes it possible to obtain estimates in broader conditions.…”

“…Standard statistical tools are found to be insufficient to assess full statistical significance. In the works [2,3], an approach is used in which the estimation of the statistical significance of the combined effect considered above should be reduced to the refutation of three null hypotheses:…”

“…This approach requires no additional assumptions. It was also used in the works [2,3] in the method of valid conditionally linear regularities(VCLR). At that, the maximum of the functional depending on the values of the correlation coefficients in the subgroups corresponding to the values of the third factor to the sides of the threshold and the sizes of these subgroups was used as the statistics of the test.…”