Cystic fibrosis (CF) is identified with a monocyte adhesion defect disease (LAD-IV). Since drug correction of CFTR can correct the adhesion defect in this white blood cell subtype, measuring the correction of this defect can be used to monitor CF patients on a therapeutic regimen. In this study, monocytes isolated from the peripheral blood of 35 CF patients were studied before and during treatment with Kaftrio or Symkevi. The results show that in 76% of patients treated with Kaftrio, and in 83% of patients treated with Symkevi, the therapy corrected the adhesion defect in monocytes. In addition, together with the recovery of adhesion, there was an average increase of 26% in respiratory capacity (FEV1) and an average reduction of 59% in the concentration of chlorine in sweat. The data, therefore, show that Kaftrio and Symkevi can correct adhesion deficits in CF monocytes. This represents the first example of pharmacological correction of a LAD phenotype. Furthermore, in most patients treated with Kaftrio or Symkevi there is a correspondence between increased adhesive function of monocytes and improved clinical parameters. The data, therefore, suggest that the measurement of monocyte adhesiveness can be used as a novel test to monitor CF patients on a therapeutic regimen.