Population
Adult surgery and obstetric patients (90 in vitro and in vivo studies).
Intervention
Visual blood loss estimation methods.
Comparison
Several methods including: gravimetric and colorimetric methods.
Outcome
The mixed effect meta-analysis showed the highest correlation to the reference for colorimetric methods (0.93), followed by gravimetric (0.77) and finally visual methods (0.61). The bias for estimated blood loss (ml) was lowest for colorimetric methods (57.59) compared to the reference, followed by gravimetric (326.36) and visual methods (456.51). Colorimetric methods offer the highest degree of accuracy in blood loss estimation.