Johns Hopkins researchers have developed a new method that could advance research into HIV’s effects on the brain by enabling scientists to pool and compare results from different types of cognitive tests without having to administer new tests to groups of patients—saving both time and resources while improving understanding of how the disease affects thinking and memory.

“Development of a refined harmonization approach for longitudinal cognitive data in people with HIV,” appears on ScienceDirect.

“This approach not only broadens the scope of research, but also holds the potential to deepen our understanding of the neurological complications faced by people living with HIV, ultimately improving clinical treatment outcomes and advancing therapeutic strategies,” says co-author Lang Lang, a PhD student in the Whiting School of Engineering’s Department of Applied Mathematics and Statistics.

One major challenge in understanding the cognitive effects of HIV is the use of different tests across studies, making it difficult to compare patients’ memory performance.

“It’s similar to trying to evaluate two students’ abilities when they take entirely different exams. Without a way to translate results from one test to another, the comparisons become unreliable, which has hindered progress in HIV neuroscience research,” says lead author and Malone affiliate Yanxun Xu, an associate professor of applied mathematics and statistics.

To solve this problem, the research team developed a harmonization process based on the second-order factor model—an innovative approach that extracts measures of underlying cognitive abilities from across tests, even when those tests are entirely different. By using correlations between areas of cognitive functioning (called “domains”) such as language skills and motor skills, the model draws on a broader understanding of how cognition works, allowing direct comparisons of memory performance even when the original studies used different tests.

The second-order factor model works in two stages. In the first, it consolidates data from various cognitive tests within a single domain, such as memory, to create a summary score. In the second stage, it integrates these domain-specific scores to create a comprehensive “general function” factor that reflects an individual’s overall cognitive health.

“By synthesizing data from diverse studies and creating a more consistent way to measure brain function, the second-order factor model could transform HIV research and help improve treatments for people living with the virus,” says Xu.

Study co-authors include Leah Rubin and Raha Dastgheyb, both professors at the Johns Hopkins School of Medicine; David Vance, a professor and associate dean at the University of Alabama at Birmingham; and Scott Letendre and Donald Franklin, both from the University of California, San Diego.