Volume Measurements in Aortic Root Assessment Using Two-Dimensional Echocardiography.

BACKGROUND: Aortic dilatation is associated with the presence of aortic diseases. Current guidelines for assessing the aortic root (AoR) depend on linear measurements acquired by two-dimensional (2D) echocardiography. We considered that real-time three-dimensional echocardiography, which correlates better with AoR volume obtained by computed tomography, is widely unavailable, and therefore, there is a need to determine the AoR volume using 2D echocardiography. METHODS: Fifty-one consecutive apparently healthy volunteers were recruited and subsequently divided into three age groups. Specified planes of acquisition and previously defined landmarks were identified, and phases of the cardiac cycle that allowed for measurement standardization were used. Volume was determined by the modified Simpson's method. RESULTS: Although the average diastolic and systolic volume measurements of the AoR dimensions were not significantly different across the three age groups in the study population, a highly significant difference was observed in the volume measurements between male and female normotensive persons, P < 0.01 in each case. AoR volume measurements were five times in the diseased compared with the normotensive individuals; however, linear measurements were only 1.5 times in size of the normal individuals. Both point and interval estimates of the volume measurements of AoR in adult normotensives in three age groups were presented as baseline information. CONCLUSIONS: We hereby present a novel way to determine the AoR volume using 2D echocardiography and the normal reference range with respect to age and gender. We also established the relevance of our measurement by comparing the normal population with two isolated diseased aortas.

Bias, precision and statistical power of analysis of covariance in the analysis of randomized trials with baseline imbalance: a simulation study.

BACKGROUND: Analysis of variance (ANOVA), change-score analysis (CSA) and analysis of covariance (ANCOVA) respond differently to baseline imbalance in randomized controlled trials. However, no empirical studies appear to have quantified the differential bias and precision of estimates derived from these methods of analysis, and their relative statistical power, in relation to combinations of levels of key trial characteristics. This simulation study therefore examined the relative bias, precision and statistical power of these three analyses using simulated trial data. METHODS: 126 hypothetical trial scenarios were evaluated (126,000 datasets), each with continuous data simulated by using a combination of levels of: treatment effect; pretest-posttest correlation; direction and magnitude of baseline imbalance. The bias, precision and power of each method of analysis were calculated for each scenario. RESULTS: Compared to the unbiased estimates produced by ANCOVA, both ANOVA and CSA are subject to bias, in relation to pretest-posttest correlation and the direction of baseline imbalance. Additionally, ANOVA and CSA are less precise than ANCOVA, especially when pretest-posttest correlation ≥ 0.3. When groups are balanced at baseline, ANCOVA is at least as powerful as the other analyses. Apparently greater power of ANOVA and CSA at certain imbalances is achieved in respect of a biased treatment effect. CONCLUSIONS: Across a range of correlations between pre- and post-treatment scores and at varying levels and direction of baseline imbalance, ANCOVA remains the optimum statistical method for the analysis of continuous outcomes in RCTs, in terms of bias, precision and statistical power.

Clinical outcomes among low back pain consulters with referred leg pain in primary care.

STUDY DESIGN: Merged data from two primary care prospective cohort studies. OBJECTIVE: To compare the clinical course of low back pain (LBP) consulters to primary care with and without self-reported referred leg pain. SUMMARY OF BACKGROUND DATA: In patients with LBP, the presence of leg pain/sciatica is considered a poor prognostic indicator, associated with more severe pain, disability, and time off work. However, questions remain about how best to identify sciatica in primary care and whether self-reported referred leg pain provides a distinct classification for primary care. METHODS: Data from two large prospective cohort studies of consecutive patients consulting with LBP in 13 general practices were merged. Using self-report data patients were divided into three subgroups: (1) those with LBP alone, (2) LBP with referred pain above the knee (LBP + above-knee), and (3) LBP with referred pain below the knee (LBP + below-knee). Unadjusted and adjusted baseline and 6-month follow-up scores on physical, psychological, and social indicators were compared between the groups using multiple regression analysis. RESULTS: Among 1247 consulters the baseline prevalence of cases with LBP alone was 465 (37%), LBP + above-knee was 308 (25%), and LBP + below-knee was 474 (38%). Baseline severity and 6-month outcomes in the consulters with referred leg pain were significantly worse compared to those with LBP alone across a wide range of clinical characteristics, although differences diminished after adjusting for baseline characteristics. CONCLUSION: The clinical course for LBP with self-reported referred leg pain is much worse. However, the fact that differences in outcome were not worse after adjustment suggests that baseline differences in severity and duration of back pain, demographic, and psychological characteristics largely explain the poorer outcomes in patients with referred leg pain. Future research needs to establish if similar results are observed among patients with clinically determined sciatica.