Introduction: In this cohort study, we investigated whether monitoring blood levels of immature neutrophils (myelocytes, metamyelocytes and band cells) differentiated patients with sepsis from those with the non-infectious (N-I) systemic inflammatory response syndrome (SIRS). We also ascertained if the appearance of circulating immature neutrophils was related to adverse outcome.
Methods: Blood samples were routinely taken from 136 critically ill patients within 48 hours of ICU entry and from 20 healthy control subjects. Clinical and laboratory staff were blinded to each other's results, and patients were retrospectively characterised into those with SIRS (n = 122) and those without SIRS (n = 14). The patients with SIRS were further subdivided into categories of definite sepsis (n = 51), possible sepsis (n = 32) and N-I SIRS (n = 39). Two established criteria were used for monitoring immature white blood cells (WBCs): one where band cells >10% WBCs and the other where >10% of all forms of immature neutrophils were included but with a normal WBC count. Immature neutrophils in blood smears were identified according to nuclear morphology and cytoplasmic staining.
Results: With the first criterion, band cells were present in most patients with SIRS (mean = 66%) when compared with no SIRS (mean = 29%; P <0.01) and with healthy subjects (0%). The prevalence of band cells was higher in definite sepsis (mean = 82%) than in patients with possible sepsis (mean = 63%; P <0.05) or with N-I SIRS (mean = 39%; P <0.001), and they had a sensitivity of 84% and a specificity of 71% for the detection of definite sepsis. With the second criterion (that is, patients with normal WBC counts), we noted that immature neutrophils did not differentiate any of the patient groups from one another. Patients who died within 1 week of blood sample provision had higher levels of myelocytes and metamyelocytes (median = 9%; P <0.05) than patients who died at 2 to 4 weeks (median =0.5%).
Conclusions: Raised blood levels of band cells have diagnostic significance for sepsis, provided that measurements are not confined to patients with normal WBC counts, whereas an increased prevalence of myelocytes and metamyelocytes may have prognostic application.