Predicting virological decay in patients starting combination antiretroviral therapy

Objective: Model trajectories of viral load measurements from time of starting
combination antiretroviral therapy (cART), and use the model to predict whether
patients will achieve suppressed viral load ( 200 copies/mL) within 6-months of starting cART.
Design: Prospective cohort study including HIV-positive adults (UK Collaborative HIV Cohort Study).
Methods: Eligible patients were antiretroviral-naïve and started cART after 1997.
Random-effects models were used to estimate viral load trends. Patients were
randomly selected to form a validation dataset with those remaining used to fit the model. We evaluated predictions of suppression using indices of diagnostic test performance.
Results: Of 9562 eligible patients 6435 were used to fit the model and 3127 for
validation. Mean log10 viral load trajectories declined rapidly for 2-weeks post-cART, moderately between 2-weeks and 3-months, and more slowly thereafter. Higher pretreatment viral load predicted steeper declines, whilst older age, white ethnicity and boosted-PI/NNRTI-based cART-regimen predicted a steeper decline from 3-months onwards. Specificity of predictions and the diagnostic odds-ratio substantially improved when predictions were based on viral load measurements up to the 4-month visit compared to the 2 or 3-month visits. Diagnostic performance improved when suppression was defined by two consecutive suppressed viral loads compared to one.
Conclusions: Viral load measurements can be used to predict if a patient will be
suppressed by 6-months post-cART. Graphical presentations of this information could help clinicians decide the optimum time to switch treatment regimen during the first months of cART.