Tuberculosis burden and its predictors among people living with HIV/AIDS at a Nigerian treatment centre: a prospective study by S. A. Olowookere, O. F. Awopeju, F. O. Fehintola, O. Arije, T. O. Ojo, O. I. Obe-Adeoye, O. A. Aina, M. O. Gbadamosi, E. G. Adepoju