Virological suppression: achieving and maintaining a VL level <50 copies/ml

Virological failure: incomplete virological response after commencing treatment or evidence of confirmed virological rebound to >200 copies/mL 

Incomplete virological response: Two consecutive VL >200 copies/ml after 24 weeks without ever achieving VL <50 copies/mL. Consideration of the baseline VL and regimen should be made as some regimens will take longer than others to suppress HIV RNA levels. In patients with a high baseline viral load [e.g. > 100,000 copies/ml] it may take longer for viral load to fall below the limit of detection; in contrast, patients treated with an integrase inhibitor are more likely to experience more rapid reduction in viral load. 

Virological rebound: failure to maintain a VL below the limit of detection (ordinarily <40-50 copies/mL) on 2 or more consecutive occasions

Low-level viraemia: a persistent VL between 50 – 200 copies/mL

Virological blip: after virological suppression, a single VL between 50 and 200 copies/ml followed by an undetectable result