The Association of Provider and Practice Factors With HIV Antiretroviral Therapy Adherence

David J. Meyers, MPH; Megan B. Cole, PhD, MPH; Momotazur Rahman, PhD; Yoojin Lee, MS, MPH; William Rogers, PhD, Roee Gutman, PhD; Ira B. Wilson, MD, MSc, FACP


AIDS. 2019;33(13):2081-2089. 

In This Article


Sample Characteristics

Over 80% of all HIV patients during the study period were successfully attributed to providers, with some variation between states in the rates of attribution (refer to Appendices 3 and 4, Our final sample included 60 496 patients with HIV contributing a total of 111 013 patient-years during our study period.

Table 1 displays patient characteristics for the overall sample and compares patients in the highest vs. lowest quintiles of adherence performance at the provider-level. The percentage of year adherent across all patients in the sample was 69.8% (SD 28.5%). Given our large sample sizes, almost all differences between patients in the lowest and highest quintiles were statistically significant, but many were also clinically large. Notably, patients attributed to low adherence providers were more often black (56.7 vs. 35.9%), younger (46.4 vs. 52.7 years old), disabled (50 vs. 42.8%), and had fewer years on average attributed to the same provider (1.3 vs. 2.4).

Provider and Practice Level Adherence Performance

Figure 1 shows the distribution of unadjusted and adjusted adherence for each provider or practice. In the unadjusted model, the median adherence for providers was 66.2% with an interquartile range of 23.0 percentage points. For practices the median adherence was 66.2% with an interquartile range of 19.8 percentage points.

Figure 1.

Distribution of crude and adjusted antiretroviral therapy adherence by provider and provider
Un-adjusted is a boxplot of the distribution of provider or practice level antiretroviral therapy Proportion of Days Covered rates. It is comprised of the mean adherence across all patients attributed to each provider or practice. The adjusted distribution comes from a model at the patient level their adherence adjusting for age, sex, race/ethnicity, regimen, chronic conditions, substance use, and state, year, and provider or practice fixed effects, then calculating the adjusted mean for each provider or practice.

After adjusting for patient characteristics, for providers, the median was 68.8% with an interquartile range of 10.4 percentage points, representing a 16.2% difference between the 25th and the 75th percentiles. For practices, the median adherence was 68.7% with an interquartile range of 9.5 percentage points representing a 15.0% difference between the 25th and the 75th percentiles.

Results of Multilevel Modeling of Patient-level Adherence

Table 2 presents the coefficients from the full regression model that includes both provider and practice random effects. Each coefficient represents a percentage point difference in the percentage of year adherent at the patient-level. At the provider and practice-level, patients seen by generalists and other specialists had a 1.6 [95% confidence interval (CI): 0.6–2.5] and 5.1 (95% CI: 4.1–6.1) percentage point greater adherence compared with those seen by infectious disease specialists (P < 0.001). A provider having an MD/DO as their credential was also associated with a 1.6 percentage point increase in adherence (P = 0.016). Patients who saw providers with greater HIV patient volume tended to have higher adherence; however, the size of the association was small: every increase in 10 patients was associated with a 0.4 percentage point increase in adherence.

At the patient-level, the factor most associated with adherence was number of years the patient was attributed to the same provider. A 1-year increase in years attributed to the same provider was associated with a 6.0 percentage point increase in percentage of year adherent (95% CI: 5.7–6.3). Substance use was associated with a lower adherence (−1.2% for drug or alcohol use diagnoses). Black patients and Hispanic patients had lower adherence rates than white, non-Hispanic patients: 4.5 percentage points (95% CI: 3.7–5.3) and 1.7 percentage points (95% CI: 0.8–2.5 percentage points) lower, respectively.

Variance Components Analysis

Table 3 presents the amount of variance attributable to each level of the model. Providers alone explained 13% of the variance, whereas practices alone explained 10.4% of the variance. Providers and practices together explained 11.9% of the variance. In the full model that included patient characteristics and random effects, providers and practices accounted for 6.8% of all variation in adherence. Patient random effects explained 452% of the total variance in adherence in this full model.

All results were largely robust to changes in model specifications and the inclusion of zip code fixed effects, as shown in the Appendix,