Paired Correlation Analysis Research Articles

Clinical Comparison of Patient-Side Fibrinogen Assay and Common Laboratory Analyzer in Pediatric Cardiopulmonary Bypass

The coagulation status of infant and pediatric patients can be severely compromised during the course of cardiopulmonary bypass due primarily to hemodilution and hypothermia. Fibrinogen level is one source of information necessary to assess the coagulation status of a patient. An accurate and expedient method to determine the fibrinogen level would allow for earlier initiation of coagulation therapy to prevent excessive postoperative bleeding. The purpose of this study was to compare two methods of determining fibrinogen level: a patient-side assay and a common laboratory analyzer. The patient-side test utilized the HemoChron Fibrinogen Assay and was performed in the operating room. The MLA 1000C was the laboratory method utilized in the hospital's coagulation laboratory. Simultaneous testing was conducted pre bypass and intraoperatively on 26 infant and pediatric patients undergoing cardiopulmonary bypass for palliation and correction of congenital heart defects. The resulting values were compared using paired t-test, regression and correlation analysis, and descriptive analysis. The values obtained by the two methods were significantly different (p<.05) at each collection time. Further analysis revealed that other variables, such as hematocrit and platelet count, affected the differences between the results of the methods. The HemoChron Fibrinogen Assay may not be a viable tool for the assessment of fibrinogen level on infant and pediatric patients undergoing cardiopulmonary bypass surgery. Further studies should be done in this patient population incorporating other confounding variables.

An analysis of side chain interactions and pair correlations within antiparallel beta-sheets: the differences between backbone hydrogen-bonded and non-hydrogen-bonded residue pairs.

Cross-strand pair correlations are calculated for residue pairs in anti-parallel beta-sheet for two cases: pairs whose backbone atoms are hydrogen bonded together (H-bonded site) and pairs which are not (non-H-bonded site). The statistics show that this distinction is important. When glycine is located on the edge of a sheet, it shows a 3:1 preference for the H-bonded site. The strongest observed correlations are for pairs of disulfide-bonded cystines, many of which adopt a close-packed conformation with each cystine in a spiral conformation of opposite chirality to its partner. It is likely that these pairs are a signature for the family of small, cystine-rich proteins. Most other strong positive and negative correlations involve charged and polar residues. It appears that electrostatic compatibility is the strongest factor affecting pair correlation. Significant correlations are observed for beta- and gamma-branched residues in the non-H-bonded site. An examination of the structures shows a directionality in side chain packing. There is a correlation between (1) the directionality in the packing interactions of non-H-bonded beta- and gamma-branched residue pairs, (2) the handedness of the observed enantiomers of chiral beta-branched side chains, and (3) the handedness of the twist of beta-sheet. These findings have implications for the formation of beta-sheets during protein folding and the mechanism by which the sheet becomes twisted.