Impaired PMN migratory capacity: a risk marker for impending infections in severe trauma patients

Objective

PMNs represent the foremost line of host defence against bacterial and fungal infections. We investigated the association between impaired PMN migratory capacity and subsequent infections in critically ill trauma patients.

Method

Twenty-six patients with different ISSs were included in a prospective study. PMN migration was measured daily in fresh whole blood in a membrane filter assay. Migration was evaluated in an automated image analyser. The relevant parameter was the percentage of PMNs migrating from the blood samples into filters upon FMLP stimulation. Migration values below the critical minimum of 6% on three consecutive days predict high infection risk, as we have repeatedly found in our numerous studies on this subject.

Results

Nine patients developed microbiologically verified infections. In comparison with the 17 noninfected patients, these patients showed reduced PMN migratory capacity 1–19 days before infection occured.

The group with infections developed a significantly lower total PMN migration (P = 0.0018); they more frequently had values below the critical limit of 6% (P = 0.0005) and low values over longer periods (P = 0.0008). When these parameters were combined, infections could be predicted with a specifity/sensivity of 82.3/88.8%. Trauma severity had no influence on PMN migration. An increase of PMN migration signalled the restoration of immunity.

Conclusion

Trauma patients with impaired PMN migratory capacity are at increased risk for infections. PMN migration tests can define the risk and may be useful for deciding when to initiate, maintain and discontinue antimicrobial treatment.