In critically ill COVID-19 patients, plasma ferritin alone does not reliably predict who benefits from the immune-modulating drug anakinra, but low baseline suPAR (a marker of immune activation) showed potential as a stratification tool. These findings suggest the need for more refined biomarker strategies in ICU COVID-19 treatment.
The REMAP-CAP trial represents one of the largest adaptive platform trials for COVID-19 treatment. This exploratory analysis focused on a specific question: can we use blood markers to identify which critically ill patients actually benefit from anakinra, an interleukin-1 receptor antagonist that dampens inflammatory response?
The researchers examined two potential "treatable traits" - measurable characteristics that might predict treatment response. Plasma ferritin, an acute phase reactant linked to inflammation and tissue damage, was analyzed in 1,243 patients. The results were underwhelming: while patients with higher ferritin levels numerically had fewer organ support-free days (OSFD), the probability that anakinra provided benefit across increasing ferritin levels was inconsistent (64%, 71%, and 21% across three ferritin groups). This suggests ferritin levels alone don't reliably identify anakinra responders. The posterior probability in unadjusted analyses was 53%, showing that ferritin stratification didn't substantially improve treatment selection.
The suPAR analysis, conducted in a smaller subset of 145 patients, produced more interesting findings. Soluble urokinase plasminogen activator receptor (suPAR) is a marker of immune cell activation and endothelial dysfunction. Patients with high baseline suPAR (≥6 ng/ml, n=85) had notably worse outcomes with median OSFD of -1.0 days compared to -1.0 to 13.0 days in low suPAR patients. Critically, the benefit profile inverted across the groups: in patients with low baseline suPAR, anakinra showed a posterior probability of benefit of 94.8% (OR 2.28, 95% CrI 0.85-6.06), whereas in high suPAR patients, this dropped to 38.6% (OR 0.88, 95% CrI 0.39-2.00). The credible intervals in both cases were wide, reflecting uncertainty, but the direction of effect was opposite.
This pattern contradicts findings from non-critically ill COVID-19 populations, where high inflammatory markers like ferritin typically predicted better responses to anti-inflammatory therapy. The authors hypothesize that critically ill patients may represent a distinct phenotype: those with extremely high inflammation may already have progressed beyond the therapeutic window for immune modulation, or they may harbor concurrent bacterial infection where dampening inflammation could be harmful. Conversely, patients with lower baseline immune activation markers might benefit from targeted IL-1 inhibition without sacrificing protective immunity.
This study does not change clinical practice for most people. Anakinra is an injectable medication used only in hospital ICUs under physician supervision for critically ill COVID-19 patients. The findings are exploratory and hypothesis-generating rather than definitive.
However, the results illustrate an important principle in precision medicine: inflammatory markers that predict severity don't automatically predict treatment response. High ferritin predicts worse outcomes in COVID-19, but measuring it doesn't tell us who will benefit from a specific anti-inflammatory drug. This distinction matters for trial design and for future attempts to personalize critical care.
For patients or families facing ICU decisions for severe COVID-19, the practical implication is that biomarker-guided treatment selection in critical care remains an area of active research. Clinicians should base treatment decisions on the totality of evidence from randomized trials, not on individual biomarker levels in isolation. The REMAP-CAP trial's broader findings on anakinra remain the reference standard, and this analysis provides context for future more refined patient selection strategies.
| Attribute | Detail |
|---|---|
| Study Type | Randomized controlled trial (exploratory subgroup analysis) |
| Sample Size | 1,243 patients (ferritin analysis); 145 patients (suPAR analysis) |
| Population | Critically ill adults within 24 hours of requiring respiratory or cardiovascular support in ICU with suspected or confirmed COVID-19 |
| Intervention | Anakinra (IL-1 receptor antagonist) vs. standard care |
| Primary Outcome | Organ support-free days (OSFD) until day 21 |
| Key Finding (Ferritin) | No consistent benefit signal across ferritin levels; ferritin does not identify anakinra responders |
| Key Finding (suPAR) | Potential benefit in low suPAR patients (94.8% posterior probability) but not high suPAR patients (38.6%) |
| Analysis Method | Bayesian cumulative logistic regression |
| Journal | Critical Care |
| PubMed ID | 42823695 |
| Trial Registration | NCT02735707 |
Remap-Cap Investigators. (2024). Evaluating plasma ferritin and suPAR as treatable traits for critically ill patients with COVID-19 treated with anakinra: an exploratory analysis of the immune modulation domain of the REMAP-CAP randomised clinical trial. *Critical Care*, 28, 31.
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