From Research Tool to Routine Test: CD38 Monitoring in HIV Patients

摘要

Background: CD38 expression on CD8+ T lymphocytes in HIV-infected patients is monitored by flowcytometry (FCM). There is however no consensus re CD38 protocols, analyses or result reporting within/between laboratories. Internal quality control measures (QC) were established for a standardized CD38protocol and a system proposed for reporting CD38 fluctuation in longitudinal HIV+ patient monitoring. Methods: A single-platform (SP) CD38/CD8 protocol was "piggy-backed" onto the standardized "pan-leucogating" CD45/CD4+ protocol. A weekly QC was established to monitor instrument stability (Flow-SET~TM) and absolute cell count accuracy reproducibility (stabilized blood product, Immuno-Trol~TM).The Mean Fluorescence Intensity (MFI) of CD38 expression on CD8+-lymphocytes was monitored on bothstabilized blood and HIV-control samples. Linearized MFI values were determined from biological con-trols, i.e. healthy donor monocytes and granulocytes, and tested as a method of reporting CD38 expres-sion on selected HIV+ patients on ART. Results: The CD45/CD4/CD8/CD3 method for lymphocyte enumeration compared well with the CD38protocol (CD45/CD4/CD8/CD38) with excellent similarity (±100%) and precision for absolute CD4 andCD8 counts (CVs < 5%). Fluorosphere MFI- (FlowSet~TM, FlowCount~TM) and color compensation valueswere exceptionally stable over time. CD38 MFI values established on monocytes as biological controlwas 4.0 and <2.0 for HIV-control lymphocytes. Conclusions: Monitoring FCM with fluorosphere MFI values, color compensation, and biological con-trols, can ensure that CD38 analyses are technologically stable. Flow cytometry is thus the preferredmethod to monitor fluctuations in CD38 MFI (CD38 molecules/cell) associated with HIV-disease progres-sion and/or response to ART and has potential for application across instruments and centers.