Key result
Drawing 5 or more blood tubes linked to ~8-fold higher vasovagal syncope risk.
Why the study?
There have been no large-scale studies investigating the incidence and predisposing factors of vasovagal syncope in the blood collection room during phlebotomy.
What are the incidence and predisposing factors for vasovagal syncope in outpatients undergoing phlebotomy?
Population
677,956 phlebotomies performed in outpatients in the blood collection room
Comparison
Phlebotomy with more than 5 blood collection tubes and waiting time over 15 min vs fewer tubes and shorter waiting time
Design
Retrospective observational study
Authors
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May support limiting tubes in outpatient phlebotomy; leaves open causality and need for prospective trials.
Observational (n=677,956)
No
What are the incidence and predisposing factors for vasovagal syncope in outpatients undergoing phlebotomy?
Odds Ratio: 8.1 (95% CI 3.76–17.5)
Absolute Event Rate: 0.016% vs 0.002%
p-value: p=<0.001
In a large-scale retrospective study, the incidence of vasovagal syncope during outpatient phlebotomy was very low (0.004%), but risk increased with the use of >5 collection tubes and waiting times >15 minutes.
Yoshimoto et al. (2020) conducted an observational in Outpatients undergoing phlebotomy (n=677,956). Use of ≥5 blood collection tubes vs. Use of <5 blood collection tubes was evaluated on Incidence of immediate vasovagal syncope (VVS) (OR 8.10, 95% CI 3.76-17.50, p=<0.001). Use of 5 or more blood collection tubes during outpatient phlebotomy was associated with a significantly higher risk of vasovagal syncope compared to fewer tubes (OR 8.10).
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