Infectious Disease
Conflation of prediction and causality in observational cohort studies of HIV and drug-resistant tuberculosis Matthew L. Romo* Matthew Romo Lucia Barcellini Molly F. Franke Palwasha Y. Khan
Observational data can answer both predictive and etiologic research questions; however, the model-building approach and interpretation of results differ based on the research goal (i.e., prediction versus causal inference). Conflation occurs when aspects of the methodology and/or interpretation that are unique to prediction or etiology are combined or confused, potentially leading to biased estimates and erroneous conclusions. Drug-resistant (DR) tuberculosis (TB) remains a major global public health threat, and living with HIV might be a predictor and/or cause of worse treatment outcomes. We conducted a rapid review using MEDLINE (2018–2023) to identify cohort studies among people with DR-TB that considered HIV status an exposure of interest and reported on TB treatment outcomes. Using signaling questions related to elements of predictive and etiologic studies, two reviewers assessed four domains of each article: (i) research question, (ii) statistical approach, (iii) presentation of results, and (iv) discussion and interpretation of results. An article was classified as conflated if any one of the domains was conflated (i.e., containing both etiologic and predictive elements) or at least two domains had discordant classifications (e.g., predictive research question domain with etiologic interpretation of results). Of 177 unique articles from our search, 40 articles met the inclusion criteria and were included in the review. Research questions were classified as unclear for 17 (43%) articles. When considering the four domains, 31 (78%) articles had evidence of conflation. The most common types of conflation were recommending or proposing interventions to modify exposures in a predictive study and having a causal interpretation of predictors. Conflation between prediction and etiology was common in the HIV and DR-TB literature highlighting the importance of increasing awareness about it and its potential consequences, and ways to avoid it.