David P Serota

The concept of “undetectable = untransmittable (U = U)” has been revolutionary in both the prevention and treatment of persons with human immunodeficiency virus (HIV). Most studies proving the concept of U = U used an HIV RNA (viral load [VL]) cutoff of 200 copies/mL to define being undetectable. Since then, increasingly sensitive commercial VL assays, sometimes down to a lower limit of detection (LLD) of 20 copies/mL, lead to confusion about the definition of “undetectable” and when someone is truly considered untransmittable. VLs between the LLD and 200 copies/mL have been associated with future virologic failure; however, no data exist to suggest that intervening in those patients leads to any meaningful benefits. In the absence of a demonstrable benefit of reporting such low VLs, we view this practice as harmful. We suggest recommendations for adjusting VL reporting and improving provider counseling, and call for research designs to mitigate the harms of overly sensitive VL testing.