CALCA and infection: In a cohort study involving 789 patients with severesepsis or septic shock in an intermediate care unit, PCT levels decreased by lessthan 15% in 72 hours and by less than 20% between the first 24 and 72 hours; thedecreases over these intervals were independent predictors of 30-day mortality, withhazard ratios (HR) of 3.9 (confidence interval - 95%CI, 1.6 - 9.5; p < 0.0001)and 3.1 (95%CI, 1.2 - 7.9; p < 0.001), respectively.(25) The common outcome in the last 3 studies was thatmost patients had pneumonia as the infection source, at frequencies of 44%, 52%, and51%, respectively.