Background: Premature babies have improved clinical outcomes when fed
breast milk with a relatively high protein content. Since there was no convenient way
of measuring the macronutrition of breast milk we used our routine laboratory
pyrogallol red dye binding method for cerebrospinal fluid microprotein (MTP) and our
routine method for serum triglyceride to determine the total protein and triglyceride
content of human breast milk.
Methods: The total protein contents of whole and defatted breast milk
samples, randomly collected from 115 nursing mothers, analysed using a pyrogallol red
dye binding assay on a Synchron CX7 Delta analyser were compared with the total
protein contents determined by dry combustion analysis. Triglyceride concentrations,
determined on the Synchron CX7 Delta analyser were compared with their respective
creamatocrits.
Results: Passing and Bablok regression analysis (95% confidence
interval) gave the following regression equations: y = 5.98(5.48 to 6.56)x-1.32(-2.02
to -0.73) where y is whole milk MTP (g/L) and x is dry combustion analysis (g/100 g);
y = 7.09 (6.54 to 7.78)x-2.44 (-3.46 to -1.67) where y is volume-corrected defatted
milk MTP (g/L) and x is dry combustion analysis (g/100 g); y = 7.52 (6.86 to
8.24)x+0.90(-2.42 to 3.37) where y is whole milk triglyceride (mmol/L) and x is
creamatocrit (%).
Conclusion: The Synchron CX7 Delta total protein and triglyceride assays
provide practical, rapid and reliable methods for the determination of the
macronutrition in human milk.
