Glossary

Abell-Kendall method: The Abell-Kendall method is a standard reference method for estimation of total serum cholesterol without interference from bilirubin, protein, and haemoglobin.

Anthropometric: Anthropometry is the science that defines physical measurements of a person's size, form, and functional capacities.

Atherosclerosis: Atherosclerosis is a specific form of arteriosclerosis. The term refers to build up of plaques in the arteries.

Arteriosclerosis: Arteriosclerosis refers to a thickening and hardening of arteries.

AutoAnalyzer N-24 method: The AutoAnalyzer N-24 method is a standard reference method for estimation of total serum cholesterol based on the ferric chloride reaction. The Abell-Kendall method was noted as the most used reference method following its introduction in 1952. The AutoAnalyzer N-24 method was found to give comparable results to the Abell-Kendall procedure with the benefit of a degree of automation [6].

Bifurcation: Bifurcation is the division of something into two parts. This describes locations where arterial branches occur.

Blood plasma: Blood plasma (sometimes called just plasma) is obtained by taking a sample of blood and removing blood cells. The red blood cells and white blood cells are removed by spinning with a centrifuge. Chemicals are added to prevent the blood's natural tendency to clot.

Blood serum: Blood serum is prepared by obtaining a blood sample, allowing formation of the blood clot, and removing the clot using a centrifuge. Both plasma and serum are light yellow in colour. Blood serum is blood plasma without clotting factors.

Cholestyramine: Cholestyramine is a medication that binds bile in the gastrointestinal tract to prevent its re-absorption. The resulting loss of bile acids is addressed by the liver by converting more serum cholesterol to bile acids to normalise levels, thus lowering serum cholesterol levels.

Cohort study: See observational study: Cohort study.

Digitalis Glycosides: Digitalis Glycosides are medications indicated for the treatment of congestive heart failure. They have a positive inotropic action, which stimulates and increases the strength of heart muscle contraction.

Eucaloric: Eucaloric means in caloric balance: at an intake designed to maintain weight.

Funnel plot: See Statistical terms in meta-analysis.

Haemodynamics: Haemodynamics is the study of blood flow.

Intima: Intima is the innermost coating or membrane of a part or organ, particularly of a vein or artery.

Lecithin: Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues composed of phosphoric acid, choline, fatty acids, glycerol, glycolipids, triglycerides, and phospholipids.

Linoleic acid: Linoleic acid is a polyunsaturated omega-6 fatty acid.

Linolenic acid: Linolenic acid is a polyunsaturated omega-3 fatty acid

Meta-analysis: Meta-analysis is a statistical technique for pooling data. Meta-analysis is one of the steps undertaken during a systematic review. Best practice methodology for systematic review and meta-analysis was defined in 2009 with the PRISMA statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [3]. The earliest use of the term meta-analysis is credited to Gene Glass [7]. Systematic review of data is always possible; meta-analysis is not always possible – it depends on the data available.

MOOSE: MOOSE is an acronym for “Meta-analysis Of Observational Studies in Epidemiology methodology” [8]. This is the best practice methodology for systematic review of observational studies.

Nosologist: Nosology is a branch of medicine that deals with classification of diseases. A nosoligst is a practitioner of disease classification.

Observational study: An observational study is where no intervention takes place. The researcher observes and assesses the strength of the relationship between an exposure and a disease variable. There are three types of observational study [9]:

-           Cohort study: A cohort study can be prospective (looking forward) or retrospective (looking back). Cohort observational studies are sometimes called longitudinal studies. The word “cohort” in epidemiology means “a group of people with defined characteristics who are followed up to determine incidence of, or mortality from some specific disease, all cause of death, or some other outcome.” (Morabia A. A History of Epidemiologic Methods and Concepts. Birkhaeuser Verlag; Basel: 2004. pp. 1–405).

-           Case-control study: A case control study looks at the present and past. The key difference between a case-control study and a cohort study is that the case-control study has a control, or unexposed, group. For example, the Richard Doll smoking study followed a number of people over time and divided them into those who developed cancer and those who didn’t. It then evaluated the smoking incidence among those who developed cancer vs. those who didn’t.

-           Cross-sectional study (prevalence study): A cross-sectional study looks at the present. It can be viewed as a ‘snap-shot’. It cannot assess cause and effect.

Occidentals: Occidentals are people from the western part of the world – the Occident

PRISMA: PRISMA is an acronym for “Preferred Reporting Items for Systematic Reviews and Meta-Analyses” [3]. See Systematic review.

Prospective Cohort study: See Observational study: cohort (prospective).

Randomised Controlled Trial (RCT): A randomised controlled trial is a study in which participants are randomly assigned (i.e., they have an equal probability of being assigned to any group) to a control group or an intervention group. Procedures are controlled to ensure that all participants in all study groups are treated the same except for the factor that is unique to their group. The unique factor is the type of intervention that they receive.

Statistical terms:

-        Effect size: The effect size is calculated as the mean (intervention) minus the mean (control), divided by the pooled standard deviations [10].

-        Egger’s regression intercept: Egger's regression intercept uses the inverse of the standard error to predict the standardised effect (the effect size divided by the standard error). The more the intercept deviates from zero, the more pronounced the asymmetry. If the p-value (1 tailed recommended) of the intercept is 0.1 or smaller, the asymmetry is considered to be statistically significant.

-        Fisher’s exact test: A statistical test of independence of rows and columns in a 2 by 2 contingency table. Its null hypothesis is that intervention does not affect outcome – the two are independent. This is rejected if the p value is small/significant.

-        Funnel plot: The funnel plot measures study size on the vertical axis as a function of effect size on the horizontal axis. Large studies appear toward the top of the graph and tend to cluster near the mean effect size. Smaller studies appear toward the bottom of the graph and are dispersed across a range of values. In the absence of publication bias studies are distributed symmetrically about the combined effect size. In the presence of bias, the bottom of the plot shows asymmetry. This reflects the fact that smaller studies, toward the bottom, are more likely to be published if they have larger than average effects, which makes them more likely to meet the criterion for statistical significance.

-        I²: is the proportion of the variance that reflects differences in true effects rather than sampling error. If there are no differences in true effects (all differences can be attributed to sampling) then I² is zero. If no differences can be attributed to sampling then I² is 100%.

-        Q: reflects the distance of each study from the mean effect (weighted, squared and summed over all studies). If all studies share the same effect size, the expected value of Q would equal the degrees of freedom. If Q is greater than df(Q) there is some dispersion of effects. If p is concomitantly <0.1 (which is the recommended criterion for this test), the excess dispersion is statistically significant.

-        T²: is the estimate of between study variance in true effects. If T² is greater than 0 there is a variation in true effect size.

Statistically significant: Some of the literature reported that findings were “significant” or “not significant”, without specifying at what level. Unless specified, it has been assumed that the significance level was p<0.05.

Systematic review: The term systematic review appears as early as 1948 in a literature search [11]. It means to review something in a methodological/systematic way. Best practice methodology for randomised controlled trials was defined in 2009 with the PRISMA statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [3].

Tallow: Tallow is a rendered form of beef or mutton fat, processed from suet.