Development and validation of decision rules to guide frequency of monitoring CD4 cell count in HIV-1 infections before starting antiretroviral therapy

Thierry Buclin, University of Lausanne
Amalio Telenti, University of Lausanne
Rafael Perera, University of Oxford
Chantal Csajka, University of Lausanne
Hansjakob Furrer, University of Bern
Jeffrey K. Aronson, University of Oxford
Paul P. Glasziou, University of Oxford

Document Type Journal Article

Published Version.

Buclin, T., Telenti, A., Perera, R., Csajka, C., Furrer, J., Aronson, J. K. & Glasziou, P. P. (2011). Development and validation of decision rules to guide frequency of monitoring CD4 cell count in HIV-1 infection before starting antiretroviral therapy. PLoS ONE 6(4): e18578.

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© 2011 Buclin et al.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Background: Although CD4 cell count monitoring is used to decide when to start antiretroviral therapy in patients with HIV-1 infection, there are no evidence-based recommendations regarding its optimal frequency. It is common practice to monitor every 3 to 6 months, often coupled with viral load monitoring. We developed rules to guide frequency of CD4 cell count monitoring in HIV infection before starting antiretroviral therapy, which we validated retrospectively in patients from the Swiss HIV Cohort Study.

Methodology/Principal Findings
: We built up two prediction rules (‘‘Snap-shot rule’’ for a single sample and ‘‘Track-shot rule’’ for multiple determinations) based on a systematic review of published longitudinal analyses of CD4 cell count trajectories. We applied the rules in 2608 untreated patients to classify their 18 061 CD4 counts as either justifiable or superfluous, according to their prior $5% or ,5% chance of meeting predetermined thresholds for starting treatment. The percentage of measurements that both rules falsely deemed superfluous never exceeded 5%. Superfluous CD4 determinations represented 4%, 11%, and 39% of all actual determinations for treatment thresholds of 500, 350, and 2006106/L, respectively. The Track-shot rule was only marginally superior to the Snap-shot rule. Both rules lose usefulness for CD4 counts coming near to treatment threshold.

: Frequent CD4 count monitoring of patients with CD4 counts well above the threshold for initiating therapy is unlikely to identify patients who require therapy. It appears sufficient to measure CD4 cell count 1 year after a count .650 for a threshold of 200, .900 for 350, or .1150 for 5006106/L, respectively. When CD4 counts fall below these limits, increased monitoring frequency becomes advisable. These rules offer guidance for efficient CD4 monitoring, particularly in resource-limited settings.


This document has been peer reviewed.