A handheld milk conductivity sensing device (Mylee) for measuring secretory activation progress in lactating women: a device validation study

BACKGROUND: Human milk electrolytes are known biomarkers of stages of lactation in the first weeks after birth. However, methods for measuring milk electrolytes are available only in laboratory or expert settings. A small handheld milk sensing device (Mylee) capable of determining on-site individual secretory activation progress from sensing the conductivity of a tiny milk specimen was developed. Here we evaluate the validity of a novel milk-sensing device (Mylee) for measuring the progress of milk maturation and secretory activation status. METHODS: Retrospective data analysis of laboratory records generated using the Mylee device. Device conductivity measurements were assessed for accuracy, reliability and stability in rigorous laboratory tests with standard materials. A set of human milk specimens (n = 167) was used to analyze the agreement between the milk maturation score and laboratory measurements of the secretory activation biomarker milk sodium [Na+]. RESULTS: The Mylee device was demonstrated to have excellent reproducibility (CV95%<5%) and accuracy (error < 5%) for conductivity measurements of a small specimen (350 µl), with good device stability and almost perfect inter-device unit reliability (ICC > 0.90). With regression analysis, we revealed excellent agreement between Mylee milk maturation (MM%) output or its raw conductivity signal and laboratory measurements of conductivity and sodium [Na+] in a dataset of milk specimens (n = 167; R2 > 0.9). The Mylee MM% score showed good predictive ability for secretary activation status, as determined by sodium threshold (18 mmol/L) in human milk specimens. CONCLUSIONS: In this study, we demonstrated the reliability and validity of the Mylee device and its ability to detect on-site milk secretory activation in a manner comparable to that of electrolyte-based methods. The novel MyLee device offers the potential to generate real-time information about the lactation stage, measured by mothers at the commodity of their home.