As a result, a simple linear regression model revealed a significant association (p < 0.25) between FEV1s (l) and sex (male sex was used as a reference), height, respiratory symptoms (SGRQ score <24 being used as a reference), history of pulmonary TB (no. being used as a reference), duration of HIV infection, duration of treatment, treatment regimen (another treatment regimen being used as a reference), current CD4 cell count, and khat chewing (no. being used as a reference). This evidence concerns the gene CD4 and HIV infectious disease.