Hasselbalch et al reported equations for estimating the thymic index of an infant at 4 and 8 months based on length and weight. The authors are from Hvidovre University, Roayl Veterinary and Agricultural University and Rigshospitalet in Denmark.
Patient selection: infants at 4 and 8 months
Parameters:
(1) length in centimeters
(2) weight in grams
(3) feeding method if 4 months old
Age in Months
Feeding
LN(thymic index) =
4
breast only
(0.0832 * (length)) + 3.199
4
partial breast
(0.0832 * (length)) + 2.915
4
formula only
(0.0832 * (length)) + 2.476
4
breast only
(0.000143 * (weight)) + 2.613
4
partial breast
(0.000143 * (weight)) + 2.326
4
formula only
(0.000143 * (weight)) + 1.902
8
NA
(0.0818 * (length)) - 2.625
8
NA
(0.000198 * (weight)) + 1.455
where:
• The equations in Table 2 (page 224) use 10^4 when 10^(-4) seems more appropriate.
However, the equations for length at 4 months do not give credible values. If the data in Figure 1 is analyzed then the following equations are derived.
Age in Months
Feeding
LN(thymic index) =
4
breast only
(0.078 * (length)) - 1.452
4
partial breast
(0.081 * (length)) - 1.9
4
formula only
(0.080 * (length)) - 2.25
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