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Regression-based reference limits and their reliability: example on hemoglobin during the first year of life
A Virtanen1, V Kairisto, K Irjala
1Central Laboratory, University Central Hospital of Turku, Finland.
Clinical Chemistry
|February 25, 1998
Summary
Regression analysis offers a way to calculate age-dependent reference limits for blood hemoglobin, but confidence intervals require careful evaluation. This study provides methods for reliable regression-based confidence intervals (CIs) in infants.
Area of Science:
- Clinical Chemistry
- Biostatistics
- Pediatric Hematology
Background:
- Regression analysis simplifies reference limit calculation, avoiding data subgrouping and enabling narrow age interval estimations.
- The reliability of regression-based reference limits, particularly their confidence intervals (CIs), has not been previously established.
- Accurate age-dependent reference limits are crucial for interpreting pediatric blood hemoglobin concentrations.
Purpose of the Study:
- To develop and validate methods for calculating reliable, age-dependent reference limits with confidence intervals (CIs) for blood hemoglobin concentrations.
- To assess the reliability of regression-based confidence intervals (CIs) for reference limits.
- To provide practical tools, including a table and equations, for calculating regression-based reference limits and their CIs.
Main Methods:
- Blood hemoglobin concentrations from newborns to 12 months were analyzed using linear regression.
- Piecewise linear regression was applied after identifying transition zones where the slope of age-dependent changes altered.
- Methods for estimating variance associated with reference limits and calculating exact and approximate CIs were developed.
Main Results:
- Age-dependent reference limits and CIs for blood hemoglobin were generated for infants aged 0-12 months.
- Regression-based CIs were evaluated by considering the convolution of two distributions.
- Piecewise linear regression yielded significantly different reference limits and CIs compared to conventional linear regression during the first two months of life, a period of rapid change.
Conclusions:
- The study provides a robust methodology for calculating reliable age-dependent reference limits and their confidence intervals for infant blood hemoglobin.
- Piecewise linear regression is essential for accurately estimating reference limits during periods of rapid physiological change in early infancy.
- The findings offer improved tools for clinical interpretation of pediatric hemoglobin levels, particularly in neonates and young infants.