Usefulness of biomarkers on infection management: with or without them?

Infectious diseases are disorders caused by many different microorganisms that produce clinical conditions with a wide variation in patient-rated symptoms and severity. Therefore, different diagnostic and prognostic tools are needed to help make the most accurate decisions at each moment of patient´s care with suspected infection. This mini review will analyse how some biomarkers reduce the level of uncertainty in the making decision process at some phases of sepsis, including prompt identification of septic patients, early initiation of empiric broad-spectrum antimicrobials, regimen and duration.

Cystatin C as an early marker of acute kidney injury in septic shock

OBJECTIVE

To describe the utility of determining plasma cystatinC concentrations in the diagnosis of acute incident kidney injury in septic shock.

PATIENTS AND METHODS

Prospective series of 50 patients with septic shock and plasma creatinine levels <2mg/dL hospitalized in an intensive care unit. Clinical and laboratory follow-ups were conducted, with measurements of cystatinC, urea and plasma creatinine levels from the diagnosis of septic shock to 5days later. The severity of the septic shock was assessed with the RIFLE scale.

RESULTS

Twenty patients (40%) developed acute kidney injury: 8 (16%) were categorized as RIFLE-R, 5 (10%) as RIFLE-I and 7 (14%) as RIFLE-F. All patients categorized as RIFLE-F required extracorporeal renal clearance. Eighteen (36%) patients died, 8 (20%) of whom had developed acute kidney injury in their evolution. There was poor correlation between plasma creatinine and cystatin C levels (r=.501; P=.001), which disappeared upon reaching any degree of renal impairment on the RIFLE scale. CystatinC levels increased earlier and were better able to identify patients who would develop serious renal function impairment (RIFLE-F) than creatinine and urea levels. The initial cystatinC levels were related to mortality at 30days (OR=1.16; 95%CI: 03-.85).

CONCLUSIONS

For patients who developed acute septic kidney injury, the plasma cystatinC levels increased before the classical markers of renal function. CystatinC also constitutes a severity biomarker that correlates with progression to RIFLE-F, the need for extrarenal clearance and, ultimately, mortality. This precocity could be useful for starting measures that prevent the progression of renal dysfunction.