title: Just add water: Accuracy of analysis of diluted human milk samples using mid-infrared spectroscopy.
abstract: OBJECTIVE
  To determine the maximum dilution of human milk (HM) that yields reliable results for protein, fat and lactose when analyzed by mid-infrared spectroscopy.
  
  
  METHODS
  De-identified samples of frozen HM were obtained. Milk was thawed and warmed (40°C) prior to analysis. Undiluted (native) HM was analyzed by mid-infrared spectroscopy for macronutrient composition: total protein (P), fat (F), carbohydrate (C); Energy (E) was calculated from the macronutrient results. Subsequent analyses were done with 1 : 2, 1 : 3, 1 : 5 and 1 : 10 dilutions of each sample with distilled water. Additional samples were sent to a certified lab for external validation.
  
  
  RESULTS
  Quantitatively, F and P showed statistically significant but clinically non-critical differences in 1 : 2 and 1 : 3 dilutions. Differences at higher dilutions were statistically significant and deviated from native values enough to render those dilutions unreliable. External validation studies also showed statistically significant but clinically unimportant differences at 1 : 2 and 1 : 3 dilutions.
  
  
  CONCLUSIONS
  The Calais Human Milk Analyzer can be used with HM samples diluted 1 : 2 and 1 : 3 and return results within 5% of values from undiluted HM. At a 1 : 5 or 1 : 10 dilution, however, results vary as much as 10%, especially with P and F. At the 1 : 2 and 1 : 3 dilutions these differences appear to be insignificant in the context of nutritional management. However, the accuracy and reliability of the 1 : 5 and 1 : 10 dilutions are questionable.
authors.forename: R W
authors.initials: RW
authors.lastname: Smith
authors.forename: D H
authors.initials: DH
authors.lastname: Adamkin
authors.forename: A
authors.initials: A
authors.lastname: Farris
authors.forename: P G
authors.initials: PG
authors.lastname: Radmacher
mesh_terms: D004041:Dietary Fats / Q000032:analysis*; D004044:Dietary Proteins / Q000032:analysis; D005260:Female; D006801:Humans; D007785:Lactose / Q000032:analysis*; D008894:Milk Proteins / Q000032:analysis*; D008895:Milk, Human / Q000737:chemistry*; D015203:Reproducibility of Results; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D004041:Dietary Fats; D004044:Dietary Proteins; D008894:Milk Proteins; D007785:Lactose
keywords: Human milk; macronutrients; mid infrared spectroscopy