Post-stratification

Analysis of covariance. In the context of clinical trials, a statistical technique used for taking account of the effect of various prognostic factors on the outcome observed, with a view to obtaining a more precise estimate of the effect of the treatment itself or in order to account for accidental bias. It is more general than post-stratification and... 

Post-stratification. The formation of relatively homogeneous groups of patients after the trial is completed for the purpose of providing a fair basis of comparison for the treatments. Treatment effects are established for each stratum by comparing like with like and are then combined in some appropriate way across strata. See also analysis of... 

Pharmacogenomics for Inclusion/Exclusion Criteria (or Stratification), or When Is It Appropriate for Pharmacogenetic and Pharmacogenomic Relationships to be Explored Post Hoc .210... 

Several participants felt that pharmacogenetics and pharmacogenomics should not be treated differently from any other covariate. In some cases, more confirmation would be required prior to using these data as inclusion/exclusion criteria (or for stratification), and pharmacogenetics and pharmacogenomics would be viewed as a covariate in the post hoc analyses. 

In order to modify asphalt, 100% acrylic latex is used. Special latices are marketed for this purpose. The latex can be post-added to asphalt emulsion followed by agitation to prevent stratification. 

Singh M, Reeder GS, Jacobsen SJ, Weston, S, Killian J, Roger VL. Scores for post-myocardial infarction risk stratification in the community. Circulation 2002 106 2309-14. 

As demonstrated by the results of CABG-PATCH and DINAMIT, risk stratification immediately post-MI remains challenging and TWA may have a role in this setting. In a study of 1041 patients post-MI with an LVEF >40% (average 55 10%), TWA was measured 48 66 days post-MI (52). An abnormal TWA had a... 

As with other risk stratification tests, the utility of SAECG may be enhanced by the presence of another test. In a post-MI population comparing TWA and SAECG, SAECG was more specific, but less sensitive than TWA (62). The highest positive predictive value (50%) was obtained when TWA and SAECG were combined. 

Baroreflex sensitivity (BRS) is a measure of the reflex bradycardia that follows an increase in systemic blood pressure. This reflex is mediated by arterial baroreceptors and may be measured after injection of phenylephrine or after spontaneous rises in blood pressure (64). Correlation between the two different tests is poor (69) and measures of baroreflex sensitivity are only moderately reproducible (70). Data on the ability of BRS to predict sudden death are conflicting. In the ATRAMI study in 1284 patients post-MI, HRV, and BRS were assessed at discharge (71). Depressed HRV and BRS carried a significant risk of cardiac mortality when both parameters were depressed the risk increased further. Thus, ATRAMI demonstrated that since BRS adds to the prognostic value of HRV, the two measures are complimentary rather than redundant. However, in another study of 700 post-MI patients, HRV or BRS was not predictive of SCD (60). BRS also does not appear useful for risk stratification in patients with nonischemic cardiomyopathy (63). 

Therefore, in patients post-MI with ischemic cardiomyopathy, NSVT may predict SCD and total mortality however, the incremental risk stratification in patients with LVEF <35% is unclear. The utility of obtaining routine Holter monitors for screening in this population is unclear and not currently recommended (77). NSVT may be more useful in patients post-MI with LVEF over the range of 35% to 40% however, it is difficult to separate the predictive ability of NSVT versus EP study in this population. In patients with nonischemic cardiomyopathy, NSVT has not been demonstrated to reliably predict SCD. 

Cardiac MRI may have a role in risk stratification for SCD due to its ability to detect myocardial scar. The use of gadolinium, which accumulates in infarcted tissue, has allowed delayed enhancement MRI to detect scar burden. Early experiments in dog models performed by coronary artery occlusion compared acute and chronic infarcts to pathologic specimens of the dog heart postmortem (89,90). Delayed enhancement MRI was remarkably accurate in imaging the infarcted tissue in comparison to the pathologic specimen. The spatial extent of hyperenhancement was the same as the spatial extent of myocyte necrosis at every stage post-MI. Reversible ischemia did not show delayed gadolinium uptake. Thus, delayed enhancement MRI can distinguish between reversible and irreversible injury, and... 

Benditt DG, Chow T, Kereiakes DJ, et al. MASTER II -Microvolt T Wave Alternans Testing for Risk Stratification of Post MI Patients. Identifier NCT00305214. http //clinicaltri-als.gov/ct2/show/NCT00305214. 

Camm AJ, Pratt CM, Schwartz PJ, et al. Mortality in patients after a recent myocardial infarction a randomized, placebo-controlled trial of azimilide using heart rate variability for risk stratification. AzimiLide post Infarct surVival Evaluation (ALIVE) Investigators. Circulation 2004 109(8) 990—6. 

Post-service examination revealed that all positive plates had undergone softening and considerable expansion. In addition, lead dioxide particles had penetrated the separator. The general condition of the positive plates was better with separators of higher fine-fibre content, which was related to the lower degree of acid stratification. 

It is noted that the specific phase morphology of the injected molded tensile specimens used in the present study may differ from the compression molded film morphology. In the case of extruded samples of polymer blends displaying macrophase separation. Van Oene (25) indicates that the dispersed phase may appear as either ribbons (stratification) or droplets independent of shear strain rate but dependent of the post-extrusion thermal history. A study of the effect of morphology and phase inversion on the mechanical properties of the incompatible PPO blends is presently in progress. 

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