age at collection
The infant's chronological age when the blood sample is obtained, critical for proper interpretation of screening results.
Full Definition
Age at collection refers to the precise time elapsed between birth and blood sample collection for newborn screening. This parameter is crucial because many analyte concentrations change rapidly during the first days of life, affecting the accuracy of screening algorithms and cutoff values. Most programs recommend collection between 24-48 hours of life to balance the need for adequate metabolic stress while avoiding false results due to physiological changes. Premature infants may require special consideration for timing based on gestational age versus chronological age.
Usage
Usage note: Always express in hours for the first few days, then transition to days for older samples.
In Context
- "The age at collection was 18 hours, requiring careful interpretation of thyroid function results." — laboratory report
- "Samples collected before 24 hours of age show increased false positive rates for several conditions." — program evaluation