[Preliminary results in standardization of flow cytometry protocols for monocytic HLA-DR measurement and their application in the follow up of septic shock].

In septic shock, the diminished HLA-DR expression on monocytes has been proposed as a marker of immunoparalysis that correlates with an increased risk for fatal outcome. The present study was designed to determine whether some differences in protocol procedures could lead to discrepant results in HLA-DR measurement. After establishing a reliable protocol, the second objective was to illustrate the immunoparalysis in patients with septic shock. HLA-DR measurement on monocytes was determined by means of flow cytometry in 54 healthy donors and 16 patients with septic shock. We demonstrated that storage temperature, storage duration before staining and red cells lysis constitute crucial steps in HLA-DR measurement. The precision results with coefficients of variation below 5%, were quite convincing for a manual immunoassay. At 48 hours after diagnosis of septic shock, we found severely decreased percentages of monocytes expressing HLA-DR in septic patients (24 +/- 4%, mean +/- SEM) in comparison with healthy donors (90 +/- 1%), p < 0.001). Furthermore, the persistence of a low level of monocytic HLA-DR (less than 50 %) at day 9 after admittance was associated with patients who died. This study illustrates the state of immunoparalysis in patients with septic shock and supports the potential interest in measuring HLA-DR expression on monocytes. However, multicenter studies are now needed to validate this parameter. Based on our analytical results, we conclude that a critical issue in such studies will be the capacity in each center to perform standardized measurement of HLA-DR. It should be remembered that this determination requires the definition of a common analytical procedure between laboratories participating in the trial.