Reliability of an Ion-Selective Electrode as a Simple Diagnostic Tool for Mastitis

• Published in: Journal of human lactation Vol. 38; no. 2; p. 262
• Main Authors: Furukawa, Kazuna, Mizuno, Katsumi, Azuma, Minami, Yoshida, Yurika, Den, Hiroki, Iyoda, Masayuki, Nagao, Saeko, Tsujimori, Yuta
• Format: Journal Article
• Language: English
• Published: United States 01.05.2022
• Subjects: Breast Feeding; Female; Humans; Ion-Selective Electrodes; Mastitis - diagnosis; Milk, Human - chemistry; Potassium - analysis; Reproducibility of Results; Sodium - analysis; ion-selective electrode; sodium; potassium; breastfeeding; mastitis
• ISSN: 1552-5732
• DOI: 10.1177/08903344221075050

Developing a simple quantitative tool for mastitis diagnosis is essential. The Ion-Selective Electrode for sodium has been reported to reliably measure sodium concentrations in human milk. To determine whether an Ion-Selective Electrode measurement of sodium:potassium ratios could serve as a diagnostic tool for mastitis and, if so, to determine the diagnostic cut-off value. A total of 107 milk samples, including 55 from milk bank donors and 52 from participants with mastitis, were studied. The sodium:potassium ratios were determined in 33 samples (without mastitis = 15; with mastitis = 18) by the Ion-Selective Electrode and ion chromatography. The remaining 74 samples (donor milk = 40; participants with mastitis = 34) were analyzed by Ion-Selective Electrode only. Values were averaged over three measurements for each method. The median postpartum months of donors and participants with mastitis were 2 and 3 months, respectively. The mean ( ) sodium:potassium ratios without and with mastitis were 0.5 (0.1) and 1.7 (1.2), respectively. A positive correlation existed between sodium:potassium ratios obtained from the two methods ( = 0.98). Area under the curve values were 0.951 (95% CI [0.904, 0.986]) for the Ion-Selective Electrode ( = 107) and 0.978 (95% CI [0.926, 1.000]) for the ion chromatography ( = 33) methods. The optimal cut-off value for the Ion-Selective Electrode method was 0.60, with 86.5% sensitivity and 92.7% specificity. The Ion-Selective Electrode was sufficiently accurate for the diagnosis of mastitis. Cohort studies are needed to explore the relationship between sodium:potassium ratios and clinical outcomes.