PRONOUNCED ELEVATION IN CIRCULATING CALCITONIN IN CRITICAL CARE PATIENTS IS RELATED TO THE SEVERITY OF ILLNESS AND SURVIVAL

Objective: To study circulating levels of calcitonin in critically ill patients in relation to the severity of illness and survival. Design: Cross-sectional and prospective. Setting: The ICU in Gavle hospital, a secondary non-teaching hospital. Patients: 37 consecutive ICU patients. Measurements and results: Serum calcium and immunoreactive calcitonin (iCT) were measured and the Apache II and the Multiple Organ Failure (MOF) scores were recorded during the first 24 h in the ICU. Patients were followed for hospital survival. Profound increase in circulating iCT was seen (mean 591, median 184, range 8 - 3445 pg/ml) in the studied sample and only 11% of the patients showed normal levels (< 40 pg/ml). iCT was higher in septic than non-septic patients (p<0.004) and was correlated to two indices of severity of illness (r = 0.50, p < 0.006 versus the Apache II score and p = 0.55, p<0.003 versus the MOF score). Furthermore, iCT was correlated to the length of stay in the intensive care unit (r = 0.56, p<0.001) and was elevated in the patients who did not survive when compared to survivors (p<0.03). iCT was not significantly related to the degree of serum calcium (mean 2.22+/-0.15 SD mmol/l). Gel chromtography in a fast protein liquid chromatography (FPLC) system of serum from 4 patients with elevated iCT disclosed that a majority of the measured CT was not due to monomeric CT, but high molecular CT. Conclusions: Pronounced elevations in circulatin iCT were seen during the first 24 h critically ill patients. As the major part of the iCT consisted of high molecular weight CT this would not induce hypocalcemia. Rather, the elevated iCT would be regarded as a part of the metabolic responses to illness.