The Importance of Attending to Underlying Statistical Assumptions

Non-parametric association analysis of additive and dominance effects of casein complex SNPs on milk content and quality in Murciano-Granadina goats

Goat milk casein proteins (αS1, αS2, β and κ) are encoded by four loci (CSN1S1, CSN1S2, CSN2 and CSN3, respectively) clustered within 250 kb in chromosome 6. In this study, 159 Murciano-Granadina goats were genotyped for 48 SNPs within the entire casein region. Phenotypes on milk yield and components were obtained from 2,594 dairy registries. Additive and dominance effects on milk composition and quality were studied using non-parametric tests and principal component analysis to prevent SNPs multicollinearity. Two deletions in exon 4 (CSN1S1 and CSN3), one in exon 7 (CSN2) and one in exon 15 (CSN1S2) have been found at frequencies ranging from 0.12 to 0.50. Bonferroni-corrected significant SNP additive and dominance effects were found for milk yield, fat, protein, dry matter and lactose, and somatic cells. Exons 15 and 7 were significantly associated with milk yield and components except for lactose and somatic cells, while exon 4 was significantly associated with milk yield and components except for protein and dry matter. SNPs' associations with somatic cells were less frequent and weaker than those with milk yield and components. As caseins increase, somatic cells decrease, reducing milk enzymatic activity and consumption suitability. Hence, including molecular information in breeding schemes may promote production efficiency, as selecting against undesirable alleles could prevent the compromises derived from their dominance effects.

An exploration of the prevalence and experience of cardiac cachexia: protocol for a mixed methods cross-sectional study

BACKGROUND

Cachexia is a complex and multifactorial syndrome defined as severe weight loss and muscle wasting which frequently goes unrecognised in clinical practice [1]. It is a debilitating syndrome, resulting in patients experiencing decreased quality of life and an increased risk of premature death; with cancer cachexia alone resulting in 2 million deaths per annum [2]. Most work in this field has focused on cancer cachexia, with cardiac cachexia being relatively understudied - despite its potential prevalence and impact in patients who have advanced heart failure. We report here the protocol for an exploratory study which will: 1. focus on determining the prevalence and clinical implications of cardiac cachexia within advanced heart failure patients; and 2. explore the experience of cachexia from patients' and caregivers' perspectives.

METHODS

A mixed methods cross-sectional study. Phase 1: A purposive sample of 362 patients with moderate to severe heart failure from two Trusts within the United Kingdom will be assessed for known characteristics of cachexia (loss of weight, loss of muscle, muscle mass/strength, anorexia, fatigue and selected biomarkers), through basic measurements (i.e. mid-upper arm circumference) and use of three validated questionnaires; focusing on fatigue, quality of life and appetite. Phase 2: Qualitative semi-structured interviews with patients (n = 12) that meet criteria for cachexia, and their caregivers (n = 12), will explore their experience of this syndrome and its impact on daily life. Interviews will be digitally recorded and transcribed verbatim, prior to qualitative thematic and content analysis. Phase 3: Workshops with key stakeholders (patients, caregivers, healthcare professionals and policy makers) will be used to discuss study findings and identify practice implications to be tested in further research.

DISCUSSION

Data collected as part of this study will allow the prevalence of cardiac cachexia in a group of patients with moderate to severe heart failure to be determined. It will also provide a unique insight into the implications and personal experience of cardiac cachexia for both patients and carers. It is hoped that robust quantitative data and rich qualitative perspectives will promote crucial clinical discussions on implications for practice, including targeted interventions to improve patients' quality of life where appropriate.