Measurements in the intensive care unit: what do they mean?

Intensivists depend upon a large number of measurements to make daily decisions in the ICU. However, the reliability of these measures may be jeopardized by the effects of therapy. Moreover, in critical illness, what is normal is not necessarily optimal. Procalcitonin, a putative marker of occult infection, is emerging as a valuable diagnostic marker in the ICU. Although questions remain regarding its specificity, an increasing body of work suggests that it is reliably elevated in the setting of infection. As demonstrated by Level and colleagues in this issue of Critical Care, its utility as a diagnostic marker is not affected by concomitant hemodialysis.