Mixed Models and Variance Components

A novel metric of reliability in pressure pain threshold measurement

Scientific Reports ◽

10.1038/s41598-021-86344-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Bernard Liew ◽

Ho Yin Lee ◽

David Rügamer ◽

Alessandro Marco De Nunzio ◽

Nicola R. Heneghan ◽

...

Keyword(s):

Mixed Models ◽

Variance Components ◽

Pain Threshold ◽

Intraclass Correlation ◽

Pressure Pain Threshold ◽

Total Variance ◽

Lumbar Region ◽

Pressure Pain ◽

Pressure Algometer ◽

Testing Protocols

AbstractThe inter-session Intraclass Correlation Coefficient (ICC) is a commonly investigated and clinically important metric of reliability for pressure pain threshold (PPT) measurement. However, current investigations do not account for inter-repetition variability when calculating inter-session ICC, even though a PPT measurement taken at different sessions must also imply different repetitions. The primary aim was to evaluate and report a novel metric of reliability in PPT measurement: the inter-session-repetition ICC. One rater recorded ten repetitions of PPT measurement over the lumbar region bilaterally at two sessions in twenty healthy adults using a pressure algometer. Variance components were computed using linear mixed-models and used to construct ICCs; most notably inter-session ICC and inter-session-repetition ICC. At 70.1% of the total variance, the source of greatest variability was between subjects ($${\sigma }_{subj}^{2}$$ σ subj 2 = 222.28 N2), whereas the source of least variability (1.5% total variance) was between sessions ($${\sigma }_{sess}^{2}$$ σ sess 2 = 4.83 N2). Derived inter-session and inter-session-repetition ICCs were 0.88 (95%CI: 0.77 to 0.94) and 0.73 (95%CI: 0.53 to 0.84) respectively. Inter-session-repetition ICC provides a more conservative estimate of reliability than inter-session ICC, with the magnitude of difference being clinically meaningful. Quantifying individual sources of variability enables ICC construction to be reflective of individual testing protocols.

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130 Utilization of Nutrack to Assess Variance Components and Heritability of Activity Traits

Journal of Animal Science ◽

10.1093/jas/skab054.030 ◽

2021 ◽

Vol 99 (Supplement_1) ◽

pp. 17-17

Author(s):

Lexi M Ostrand ◽

Melanie D Trenhaile-Grannemann ◽

Garrett See ◽

Ty B Schmidt ◽

Eric Psota ◽

...

Keyword(s):

Animal Model ◽

Mixed Models ◽

Variance Components ◽

Average Speed ◽

Genetic Variances ◽

Sow Longevity ◽

Selection Decisions ◽

Recorded Data ◽

Residual Variances ◽

And Behavior

Abstract Overall activity and behavior are integral components of sows remaining productive in the herd. This investigation studied overall activity of group housed replacement gilts and the heritability of various activity traits. Beginning around 20 wk of age, video recorded data of approximately 75 gilts/group for a total of 2,378 gilts over 32 groups was collected for 7 consecutive d using the NUtrack System, which tracks distance travelled (m), avg speed (m/s), angle rotated (degrees), and time standing (s), sitting (s), eating (s), and laying (s). The recorded phenotypes were standardized to the distribution observed within a pen for each group. The final values used for analysis were the average daily standardized values. Data were analyzed using mixed models (RStudio V 1.2.5033) including effects of sire, dam, dam’s sire and dam, dam’s grandsire and granddam, farrowing group, barn, pen, and on-test date. Sire had an effect on every activity trait P < 0.001), and dam had an effect on average speed (P < 0.001). The dam’s sire had an effect on all activity traits (P < 0.001) and the dam’s grandsire had an effect on average speed (P < 0.001). Heritabilities and variance components of activity traits were estimated in ASReml 4 using an animal model with a two-generation pedigree. Genetic variances are 0.17 +/- 0.029, 0.19 +/- 0.034, and 0.11 +/- 0.024, residual variances are 0.37 +/- 0.023, 0.41 +/- 0.027, and 0.41 +/- 0.022, phenotypic variances are 0.54 +/- 0.018, 0.60 +/- 0.020, and 0.52 +/- 0.016, and heritabilities are 0.32 +/- 0.048, 0.32 +/- 0.049, and 0.21 +/- 0.044 for average speed, distance, and lie respectively. NUtrack offers potential to aid in selection decisions. Given the results presented herein, continued investigation into these activity traits and their association with sow longevity is warranted.

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