Knowledge Item: CA-Technical Issues-10
Scaling Criteria for Viral Load Outcomes

In six projects, viral load data were collected between 1996 and 1999. During this time, there were significant advancements in the methods of assessing viral loads and their sensitivity. In addition, several different methods for assaying for viral loads were used and developed including PCR and bDNA 2 and bDNA 3. This Knowledge Item suggests four criteria for quantifying a clinically significant change in viral load over time, and examines the implications of each.

It should be emphasized that the criteria used here for a successful outcome are somewhat less stringent than those used in 2000 when this Knowledge Item was created. Viral load results were less sensitive during some of the years at some of the sites than the commonly accepted current undetectable standards of 400 copies (or 50 copies for a "sensitive" test). Additionally, in the literature, both criteria of .3 log units change and .5 log units change are used for a clinically significant drop in viral loads, usually defined as occurring after a period of six months.

Pragmatically examining the data that could be obtained from these projects, we defined a successful outcome in four different ways. Given everything we know about the distributions of the data, the tests that were used, the way that the data were recorded, and consistency among six sites after equating for different viral load testing methods, we believe that Method II (a viral load change over time of at least .3 logs or a follow-up test that is undetectable at the threshold of 3.01 logs) is the best criterion for this evaluation. It may be appropriate to use a more stringent criterion in subsequent studies with other datasets.

Knowledge Base Citation: The Knowledge Base and this Knowledge Item were designed and authored by G. J. Huba, Ph.D.; in collaboration with Lisa A. Melchior, Ph.D.; A. T. Panter, Ph.D.; and the staff of The Measurement Group. Cite this work as "Huba, G. J., Melchior, L. A., and Panter, A. T. (1998 - 2001). The Measurement Group Knowledge Base on HIV/AIDS Care. On the World Wide Web: http://www.TheMeasurementGroup.com."

Questions or Comments: Contact The Measurement Group.

Use of Knowledge Base Information: Acceptable Uses and Limitations.

Collaborators from Participating Projects: Cooperative Agreement Steering Committee 1999. 

Participating Projects: This Knowledge Base is based on the service delivery experiences of 27 Cooperative Agreement Projects on Innovative Models of HIV/AIDS Care. These projects and the Evaluation and Dissemination Center which produced this Knowledge Base were funded by the Health Resources and Services Administration (HRSA), HIV/AIDS Bureau (HAB) as Special Projects of National Significance (SPNS) between 1994 and 1999. Click the Model Programs button above for descriptions of the projects that contributed to this specific Knowledge Item, a list of key staff, and project grant numbers.

Why This Evaluation was Conducted: Editorial.

More Information: Design of this Knowledge Base.

Recommended Citation Format for Web Materials: American Psychological Association Publication Manual Section, Revised 2001.

Work on the Knowledge Base and the cross-cutting evaluation was supported in part by Grant Number 5 U90 HA 00030-05 from the Health Resources and Services Administration (HRSA), HIV/AIDS Bureau's (HAB) Special Projects of National Significance (SPNS). The contents of this Knowledge Base are solely the responsibility of The Measurement Group and do not necessarily represent the official views of HRSA or HRSA/HAB's Special Projects of National Significance nor may they represent the positions of the individual grantees whose projects are included in the cross-cutting evaluation.

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