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Updated: Jul 22, 2025

Author Spotlight: Advancing Immune Monitoring in Critical Care Patients Using Whole Blood Assays
Published on: September 20, 2024
The identification of diurnal variations on circulating immune cells by finger prick blood sampling in small sample
Dayna Bushell1, Jonathan Kah Huat Tan2, Jessica Smith2
1Faculty of Health Sciences and Medicine, Bond University, Robina, Australia.
Objective:
There are well-described impacts of biological rhythms on human physiology. With the increasing push for routine blood tests for preventative medical care and clinical and physiological research, optimizing effectiveness is paramount. This study aimed to determine whether it is feasible to assess diurnal variations of peripheral lymphocyte prevalence using finger prick blood in a small sample size.
Methods:
Using polychromatic flow cytometry, the prevalence of lymphocytes was assessed using 25 µL fingertip blood samples at 8 AM and 5 PM from 8 participants.
Results:
TH cells and B cells showed significantly higher percentages in the 5 PM samples, whereas NK cells demonstrated a significantly higher morning percentage. T cells, leukocytes, and cytotoxic T cells showed no significant changes.
Conclusion:
The detection of diurnal variations demonstrates that small blood volumes can be used to detect lymphocyte variations. The lower blood volume required provides a new testing method for clinical and research settings.
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