Orthostatic change in shock index: comparison with traditional tilt test definitions

To determine whether the orthostatic change in the shock index or published tilt test criteria better discriminated normal individuals from those with moderate acute blood loss.

Postural vital signs were recorded in a standardized manner before and after an elective 450-mL phlebotomy associated with blood donation in healthy volunteers. Paired comparisons of the sensitivity of each of 3 published tilt test criteria were made against the sensitivity of an orthostatic change in shock index (OCSI) at the threshold for OCSI yielding the same specificity. Subjects were prospectively divided into group 1 (age < 65 years) and group 2 (age > or = 65 years).

A total of 336 healthy euvolemic adult blood donors were studied over a 1-year period (group 1 = 292; group 2 = 44). For each published criterion for a positive tilt test (for both groups), OCSI had the same or higher sensitivity for a chosen specificity. No sensitivity difference was statistically significant. An OCSI > or = 0 was 99%/98% sensitive and 10%/10% specific (group 1/group 2) for a 450-mL blood loss; whereas an OCSI > or = 0.25 was 28%/23% sensitive and 92%/100% specific (group 1/group 2).

The OCSI discriminates normal individuals from those with acute moderate blood loss as well as previously published tilt test definitions do.