Year: 2026
Type: article
Study design: Observational Study
Abstract: Salivary secretory immunoglobulin A (sIgA) is a biomarker of mucosal immunity, but its day-to-day variability hampers interpretation of single-timepoint measurements. We sampled saliva daily from 46 healthy adults for 56 consecutive days, extracted 23 time-series features per trajectory and retained twelve for clustering. Clustering of component scores gave three groups: Stable-balanced ( n = 26; intermediate levels, low variability), High-variable ( n = 7; high concentrations, large fluctuations) and Low-unstable ( n = 13; lowest concentrations, greatest variance instability). Neither the gap statistic nor a parametric bootstrap null supported three natural clusters (silhouette 0.283, P = 0.246); we therefore present an exploratory stratification. Mean level and variability drifted little between the two halves in 18/25 (72.0%, 95% CI 52.4–85.7), 5/7 (71.4%, 35.9–91.8) and 4/13 participants (30.8%, 12.7–57.6) respectively, intervals that overlap widely. Individual-level prediction was poor; the residual component held 75–85% of the variance (an upper bound). Cough was most frequent in the Low-unstable group (5/13, 38.5%, 17.7–64.5, versus 3/26 and 0/7), but this exploratory association was not significant ( P = 0.072). A single measurement therefore cannot separate an individual’s level from day-to-day fluctuation: characterising salivary sIgA requires repeated sampling over weeks, for which this stratification is a starting point.
Source: Scientific Reports
Authors: Yu Akiyama, Takahiro Shiga, Hirotaka Minagawa, Tomoko Fujita, Ikuo Shiratori
Institution: NEC Solution Innovators, Ltd. (Japan)
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,690
OpenAlex ID: W7214218792