Statistical analysis
Normality of continuous variables was quantified using the Shapiro-Wilk
test and was reported as the mean (standard deviation, SD) and the
median [inter-quartile range, IQR] for parametric and non-parametric
data respectively. Two group comparisons of continuous data for those
with and without CMD was performed using a non-paired t-test and
Wilcoxon rank-sum tests respectively. Comparisons between the MBFR
< 2.0 group and the MBFR ≥ 2.0 group were undertaken using a
Fisher’s Exact Test.
In univariate and multivariate analysis, septal mitral annular E/e’ was
used as the main outcome variable while known influencers of septal
mitral annular E/e’ (age, gender, diabetes, hypertension, smoking
status, Body Mass Index (BMI), fasting TG, fasting LDL, MBFR and Hs-CRP)
were used as the input variables. For multivariate analysis, an initial
fully saturated model was constructed using all the known predictor
variables. Non-significant predictors were sequentially deleted, and the
model re-run. Likelihood ratio testing was employed to quantify
significant differences, or lack thereof, between model iterations. The
final models only contained the significant predictors. Results are
reported as regression slope (β) and its level of significance. Where
required, inferential analysis was performed using standard regression
techniques except in the case of a dichotomous outcome variable, where
logistic regression was employed. Predictor variables were tested for
co-linearity using a standard Pearson’s correlation. Variables with
correlation coefficients (R) greater than ±0.80 were considered
co-linear with one or other excluded largely on empirical grounds. Where
appropriate, dummy variables were used when examining the significance
of categorial predictors and all two-way interactions were tested for
significance. Finally, all statistical models were tested for adequacy
using appropriate regression diagnostics with regression residuals
tested for normality using the Shapiro-Wilk test and for homoscedascity
using the Breusch-Pagan test.
Statistical analysis was performed using a propriety statistical package
(STATA version 15.1) with the level of significance set at p <
0.05.