{
  "abstract": "Background The Proportion of Days Covered (PDC) is widely used to measure antiretroviral therapy (ART) adherence, with a threshold of ≥90% conventionally defining adequate adherence. Empirical confirmation of this threshold in contemporary real-world cohorts, particularly in the context of the UNAIDS 95% virological success target, remains clinically relevant. In this study, we aimed to characterise the relationship between PDC and virological outcomes across the full adherence spectrum.Methods Observational retrospective cohort study including all people living with HIV (PLWH) attending our HIV Outpatient Clinic between January 2024 and June 2025, on stable ART for at least 6 months. Adherence was measured by the Proportion of Days Covered (PDC) from pharmacy refill records. The virological outcome was the worst HIV-RNA recorded during follow-up. The probability of achieving HIV-RNA <200 cp/mL across the PDC spectrum was modelled using logistic regression with a natural spline (df=4), with 95% confidence intervals. Virological outcome distribution across PDC bins was summarised as proportions in three categories: suppressed (<50 cp/mL), low-level viremia (50–200 cp/mL), and overt viremia (>200 cp/mL). Independent predictors of virological success were identified by multivariable logistic regression.Results Among 1,086 patients with available viral load data, the forgiveness curve demonstrated a steep increase in virological success probability as PDC approached 90%, with the curve reaching and exceeding the 95% success threshold precisely at PDC = 90% ( figure 1A). In the PDC 90–94% bin, 95.2% of patients achieved HIV-RNA <200 cp/mL, meeting the WHO target (figure 1B). Virological suppression (<50 cp/mL) exceeded 90% in patients with PDC ≥90% and increased progressively with higher adherence. On multivariable logistic regression (table 1), each 10% increment in PDC was independently associated with significantly higher odds of virological success (aOR 1.51, 95% CI 1.29–1.77; p<0.001), after adjustment for age, sex, region of origin, years on ART, baseline CD4 count, and ART switch during follow-up. Origin from the WHO African region (aOR 0.34, 95% CI 0.18–0.64; p<0.001) and higher baseline CD4 count (aOR 1.16 per 100 cells/μL, 95% CI 1.05–1.29; p=0.005) were additional independent predictors.Conclusions In this real-world cohort, a PDC threshold of 90% corresponds to the UNAIDS 95% virological success target, providing empirical validation of the conventional 90% PDC cutoff. These findings support the use of PDC ≥90% as a clinically meaningful and operationally actionable adherence benchmark in routine HIV care.Abstract P45 Figure 1ART forgiveness - virological outcomes by adherence levelAbstract P45 Table 1Adjusted logistic regression: predictors of virological success (HIV-RNA < 200 cp/mL) among the 1086 patients included in the cohort",
  "authors": [
    {
      "affiliations": [
        "Infectious and Tropical Diseases Unit, Padua University Hospital, Padua, Italy"
      ],
      "name": "FV Segala"
    },
    {
      "affiliations": [
        "Infectious and Tropical Diseases Unit, Padua University Hospital, Padua, Italy"
      ],
      "name": "E Vania"
    },
    {
      "affiliations": [
        "Hospital Pharmacy Unit, Azienda Ospedale-Università Padova, Padua, Italy"
      ],
      "name": "D Mengato"
    },
    {
      "affiliations": [
        "Infectious and Tropical Diseases Unit, Padua University Hospital, Padua, Italy"
      ],
      "name": "D Leoni"
    },
    {
      "affiliations": [
        "Infectious and Tropical Diseases Unit, Padua University Hospital, Padua, Italy"
      ],
      "name": "S Gardin"
    },
    {
      "affiliations": [
        "Infectious and Tropical Diseases Unit, Padua University Hospital, Padua, Italy"
      ],
      "name": "A Ferrari"
    },
    {
      "affiliations": [
        "Hospital Pharmacy Unit, Azienda Ospedale-Università Padova, Padua, Italy"
      ],
      "name": "G Berti"
    },
    {
      "affiliations": [
        "Infectious and Tropical Diseases Unit, Padua University Hospital, Padua, Italy"
      ],
      "name": "L Sasset"
    },
    {
      "affiliations": [
        "Infectious and Tropical Diseases Unit, Padua University Hospital, Padua, Italy",
        "Department of Molecular Medicine, University of Padua, Padua, Italy"
      ],
      "name": "A Cattelan"
    }
  ],
  "title": "P45 Validation of the 90% proportion of days covered threshold against the WHO 95% virological success target in people living with HIV",
  "uid": "f3e5b45d-f651-5fbb-a3a6-7944eb39cd73"
}