Table 1 Summary of key biological and technical variables for each cohort. SD refers to standard deviation, QC refers to quality control
From: The application of epiphenotyping approaches to DNA methylation array studies of the human placenta
V-NORM | V-SSRI | QF2011 | p value* | |
|---|---|---|---|---|
n | 35 | 64 | 105 | |
Biological variables | ||||
Gestational age at birth (mean weeks (SD)) | 39.0 (1.1) | 39.5 (1.3) | 39.4 (1.2) | 0.29 |
Infant sex (n male (%)) | 19 (54.3) | 33 (51.6) | 59 (56.2) | 0.84 |
Infant birthweight (mean grams (SD)) | 3412.5 (537.8) | 3451.7 (460.7) | 3584.2 (403.4) | 0.06 |
Infant birthweight (mean Z-score (SD)) | − 0.02 (1.08) | − 0.02 (0.81) | 0.28 (0.82) | 0.04 |
Placental efficiency | − 0.09 (1.1) | − 0.10 (0.93) | 0.10 (0.99) | 0.37 |
Population | British Columbia, Canada | British Columbia, Canada | Queensland, Australia | |
Self-reported ethnicity (n (%)) | < 0.001 | |||
White | 14 (40.0) | 48 (75.0) | 102 (97.1) | |
Asian | 12 (34.3) | 6 (9.4) | 1 (1.0) | |
Black | 0 | 1 (1.6) | 1 (1.0) | |
Other | 8 (22.9) | 1 (1.6) | 0 (0.0) | |
Missing | 1 (2.9) | 1 (1.6) | 0 (0.0) | |
Technical variables | ||||
Processing time (median hours (SD)) | 2.9 (18.9) | 28.7 (59.8) | Approximately 1 h | |
Storage | − 20 °C | − 20 °C | Snap frozen liquid nitrogen | |
DNA extraction method, location | Salt extraction, Vancouver | Salt extraction, Vancouver | Qiagen DNeasy blood and Tissue kit, Montreal, Canada | |
Number of technical replicates | 4 | 0 | 8 | |
EPIC batch distribution (n (%)) | ||||
Batch 1 | 0 (0.0) | 64 (100.0) | 94 (89.5) | |
Batch 2 | 18 (51.4) | 0 (0.0) | 0 (0.0) | |
Batch 3 | 16 (45.7) | 0 (0.0) | 11 (10.5) | |