Table 1.
The Influence of Infant Demographics and Collection Procedures on Neonatal TSH
| Mean TSH (mIU/L)±SD | r2 | 1 P-value | r2 | 2 P-value | |
|---|---|---|---|---|---|
| Gestational age N=698 | 0.057 | <0.0001 | 0.060 | <0.0001* | |
| 23–28 wk (N=156) | 4.4±2.9 | ||||
| 29–32 wk (N=246) | 5.8±3.8 | ||||
| 33–36 wk (N=296) | 6.5±3.8 | ||||
| Birth weight N=698 | 0.034 | <0.0001 | 0.060 | 0.67 | |
| <1,250 g (N=185) | 5.0±3.6 | ||||
| 1,250–1749.9 g (N=179) | 5.6±3.5 | ||||
| 1,750–2,249.9 g (N=174) | 6.2±3.6 | ||||
| ≥2,250 g (N=160) | 6.4±4.0 | ||||
| Age at sample collection N=698 | 0.003 | 0.52 | 0.069 | 0.03 | |
| 24–36 hrs (N=588) | 5.8±3.6 | ||||
| 36–48 hrs (N=88) | 5.7±4.1 | ||||
| 48–60 hrs (N=18) | 4.8±.3.0 | ||||
| 60–72 hrs (N=4) | 6.5±6.6 | ||||
| Length at birth N=494 | 0.013 | 0.10 | 0.075 | 0.03 | |
| <25th (27–38.5 inches) (N=125) | 5.6±3.9 | ||||
| 25–50th (39–42.5 inches) (N=127) | 5.6±3.5 | ||||
| 50–75th (43–46 inches) (N=149) | 5.9±3.4 | ||||
| >75th (46.5–53.5 inches) (N=93) | 6.6±4.1 | ||||
| Head circumference at birth N=507 | 0.025 | 6x10−3 | 0.068 | 0.13 | |
| <25th (21–27.5 inches) (N=139) | 5.3±3.9 | ||||
| 25–50th (28–30 inches) (N=136) | 5.8±3.7 | ||||
| 50–75th (30.5–32 inches) (N=134) | 6.5±3.7 | ||||
| >75th (32.5–45.5 inches) (N=98) | 6.1±3.8 | ||||
| Season of Birth N=698 | 0.013 | 0.03 | 0.071 | 0.02 | |
| Winter (Dec-Feb) (N=182) | 6.1±3.7 | ||||
| Spring (Mar-May) (N=153) | 5.9±3.6 | ||||
| Summer (Jun-Aug) (N=182) | 5.2±3.5 | ||||
| Fall (Sep-Nov) (N=181) | 5.9±3.9 | ||||
| Year N=698 | 0.004 | 0.10 | 0.063 | 0.05 | |
| 2000–2004 (N=310) | 5.5±3.5 | ||||
| 2005–2009 (N=388) | 6.0±3.9 | ||||
| Major Assay Change N=698 | 0.002 | 0.54 | 0.060 | 0.42 | |
| Change #1 (N=3) | 5.6±3.7 | ||||
| Change #2 (N=433) | 5.7±3.7 | ||||
| Change #3 (N=262) | 5.9±3.7 | ||||
| Infant Gender N=698 | 0.006 | 0.05 | 0.065 | 0.02 | |
| Male (N=391) | 6.1±4.0 | ||||
| Female (N=307) | 5.4±3.3 | ||||
| Infant Race N=698 | <0.001 | 0.89 | 0.058 | 0.58 | |
| White (N=603) | 5.8±3.7 | ||||
| Non-White/Unknown (N=95) | 5.8±4.0 | ||||
| Multiple Birth N=698 | <0.001 | 0.76 | 0.058 | 0.80 | |
| Singleton (N=557) | 5.7±3.7 | ||||
| Twin/Multiple (N=141) | 5.8±3.9 | ||||
| Feeding method at birth N=538 | 0.020 | 0.01 | 0.066 | 0.23 | |
| Bottle (N=47) | 6.3±3.8 | ||||
| Breast (N=238) | 6.1±3.9 | ||||
| Both (N=12) | 6.3±3.7 | ||||
| NPO (N=241) | 5.3±3.6 | ||||
| Total parenteral nutrition at birth N=698 | <0.001 | 0.52 | 0.059 | 0.30 | |
| No (N=631) | 5.8±3.7 | ||||
| Yes (N=67) | 5.7±4.2 |
1
P-value: single variable one-way ANOVA.
2
P-value: ANOVA adjusted for gestational age.
*
This model includes adjustment for birth weight. NPO = nil per os - nothing by mouth, Major Assay Change is defined as a manufacture’s kit change which could alter the assay variability in TSH levels.