Combination of biphasic transmittance waveform with blood procalcitonin levels for diagnosis of sepsis in acutely ill patients

Objectives: To assess the diagnostic utility of combining measurement of blood procalcitonin (PCT) concentrations with the presence of a biphasic transmittance waveform (BPW) from the activated partial thromboplastin time (aPTT) to identify sepsis in critically ill patients. Design: Prospective observational study. Setting: Thirty-one-bed university hospital department of medico-surgical intensive care. Patients: Two hundred consecutive adult patients admitted to the department during a 3-month period. Measurements and Main Results: aPTT waveform analysis was performed on admission and daily throughout the intensive care unit (ICU) stay. Receiver operating characteristic curves were created to determine the best threshold values of BPW and PCT for prediction of sepsis. Of the 200 patients, 63 (32%) had sepsis during the ICU stay; 29 (15%) patients were diagnosed with sepsis at admission. Using a threshold value of BPW slope_1 = -0.075%T/sec, 37 patients (19%) had a BPW at ICU admission and 84 (42%) at some time during the ICU stay. At this threshold, 23 of the patients (62%) with a BPW at admission and 51 (61%) with a BPW during the ICU stay were diagnosed with sepsis. Using a cut-off value of 1 ng/ml, 60 patients (30%) had abnormal PCT at admission, and 86 during the ICU stay. At this threshold, 24 of the patients (40%) with abnormal PCT at admission and 52 (60%) with abnormal PCT during the ICU stay were diagnosed with sepsis. Thirty patients had a BPW and an abnormal PCT, and 23 (77%) of these had sepsis. Of the other 170 patients, only six patients (4%) had sepsis. Hence, the sensitivity of the combination of BPW and PCT at admission was 79% and specificity 96%; the negative predictive value was 96%. Conclusion: aPTT waveform analysis is an easy and rapid method for identification of sepsis; its combination with PCT increases its specificity.